- Catalytic degradation of an organophosphorus agent at Zn-OH sites in a metal-organic framework
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Chemical warfare agents (CWAs), and in particular organophosphorus nerve agents, still pose a significant threat to society due to their continued use despite international bans. While nature has constructed a variety of enzymes that are capable of rapidly hydrolyzing organophosphorus substrates, the poor stability of enzymes outside of buffered solutions has limited their use in practical applications, such as in filters or on protective suits. As a result, we have explored the use of metal-organic frameworks (MOFs) as robust and tunable catalytic materials in which the nodes can be tailored to resemble the active sites found in these enzymes. We identified the Zn-based MOF, MFU-4l, as a promising hydrolysis catalyst due to the presence of Zn(II)-OH groups on the nodes, which are structurally reminiscent of the active sites in carbonic anhydrase (CA), a Zn-based enzyme that has been shown to efficiently catalyze the hydrolysis of phosphate esters. Indeed, MFU-4l can rapidly hydrolyze both the organophosphorus nerve agent, GD, and its simulant, DMNP, with half-lives as low as 1 min, which is competitive with the some of best heterogeneous hydrolysis catalysts reported to date.
- Mian, Mohammad Rasel,Islamoglu, Timur,Afrin, Unjila,Goswami, Subhadip,Cao, Ran,Kirlikovali, Kent O.,Hall, Morgan G.,Peterson, Gregory W.,Farha, Omar K.
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- Influence of activated carbons on the kinetics and mechanisms of aromatic molecules ozonation
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Companies have been looking for new methods for treating toxic or refractory wastewaters; which can mainly be used prior to or after or in connexion with biological treatment processes. This paper compares conventional ozone oxidation with activated carbon (AC) promoted ozone oxidation, which helps developing a mechanism involving HO{radical dot} radical. For a compound which is quite easy to oxidise, like 2,4-dichlorophenol (2,4-DCP) conventional ozonation is efficient enough to remove the initial molecule. The mechanism involved mainly consists of an electrophilic attack on the aromatic ring, which is activated by the donor effect of the -OH group, then followed by a 1,3 dipolar cycloaddition (Criegee mechanism) that leads to aliphatic species, mainly carboxylic acids. Yet, the addition of AC, through the presence of HO{radical dot} radical, enhances the removal of these species which are more refractory. For a refractory compound like nitrobenzene (NB), with a de-activated aromatic ring because of the attractive effect of -NO2, conventional ozonation is inefficient. On the contrary, this molecule can be quite easily removed with AC promoted oxidation and it is found that the mechanism (electrophilic attack followed by a 1,3 dipolar cycloaddition) is quite similar to the one corresponding to conventional ozonation, but with less selectivity. For both molecules, a mass balance has established that the by-products accounting for more than 75% of the remaining COD can be quantified. A significant part is composed of carboxylic acids (acetic, oxalic, etc.), which could afterwards be easily removed in an industrial wastewater treatment process followed by a final biological treatment step.
- Merle,Pic,Manero,Mathé,Debellefontaine
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- Biomimicking, metal-chelating and surface-imprinted polymers for the degradation of pesticides
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Molecularly imprinted polymer beads (PIBs) and non-imprinted (control) polymer beads (NIBs) have been prepared from methacryloylhistidine-Co2+, -Ni2+, and -Zn2+ monomers and applied as catalyst in the hydrolysis of paraoxo
- Erdem, Murat,Say, Ridvan,Ers?z, Arzu,Denizli, Adil,Türk, Hayrettin
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- A simple DNase model system comprising a dinuclear Zn(II) complex in methanol accelerates the cleavage of a series of methyl aryl phosphate diesters by 1011-1013
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The di-Zn(II) complex of 1,3-bis[N1,N′1-(1,5,9- triazacyclododecyl)]propane with an associated methoxide (3:Zn(II) 2:-OCH3) was prepared and its catalysis of the methanolysis of a series of fourteen methyl aryl phosphate diesters (6) was studied at sspH 9.8 in methanol at 25.0 ± 0.1°C. Plots of kobs vs [3:Zn(II)2: -OCH3]free for all members of 6 show saturation behavior from which KM and kcatmax were determined. The second order rate constants for the catalyzed reactions (k catmax/KM) for each substrate are larger than the corresponding methoxide catalyzed reaction (k2-OMe) by 1.4 × 108 to 3 × 109-fold. The values of kcatmax for all members of 6 are between 4 × 10 11 and 3 × 1013 times larger than the solution reaction at sspH 9.8, with the largest accelerations being given for substrates where the departing aryloxy unit contains ortho-NO 2 or C(=O)OCH3 groups. Based on the linear Bronsted plots of kcatmax vs sspK aof the phenol, βIg values of -0.57 and -0.34 are determined respectively for the catalyzed methanolysis of regular substrates that do not contain the ortho-NO2 or C(=O)OCH3 groups, and those substrates that do. The data are consistent with a two step mechanism for the catalyzed reaction with rate limiting formation of a catalyst-coordinated phosphorane intermediate, followed by fast loss of the aryloxy leaving group. A detailed energetics calculation indicates that the catalyst binds the transition state comprising [CH3O -:6]?, giving a hypothetical [3:Zn(II) 2:CH3O-:6]? complex, by -21.4 to -24.5 kcal/mol, with the strongest binding being for those substrates having the ortho-NO2 or C(=O)OCH3 groups.
- Neverov, Alexei A.,Liu, C. Tony,Bunn, Shannon E.,Edwards, David,White, Christopher J.,Melnychuk, Stephanie A.,Brown, R. Stan
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- Guanidine based self-assembled monolayers on Au nanoparticles as artificial phosphodiesterases
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Gold nanoparticles passivated with a long chain alkanethiol decorated with a phenoxyguanidine moiety were prepared and investigated as catalysts in the cleavage of the RNA model compound HPNP and diribonucleoside monophosphates. The catalytic efficiency and the high effective molarity value of the Au monolayer protected colloids points to a high level of cooperation between the catalytic groups.
- Salvio, Riccardo,Cincotti, Antonio
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- Structural flexibility enhances the reactivity of the bioremediator glycerophosphodiesterase by fine-tuning its mechanism of hydrolysis
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The glycerophosphodiesterase from Enterobacter aerogenes (GpdQ) belongs to the family of binuclear metallohydrolases and has attracted recent attention due to its potential in bioremediation. Formation of a catalytically competent binuclear center is prom
- Hadler, Kieran S.,Mitic, Natasa,Ely, Fernanda,Hanson, Graeme R.,Gahan, Lawrence R.,Larrabee, James A.,Ollis, David L.,Schenk, Gerhard
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- A unique nickel system having versatile catalytic activity of biological significance
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A new dinuclear nickel(ll) complex, [Ni2(LH2)(H 2O)2(OH)(NO3)](NO3)3 (1), of an "end-off" compartmental ligand 2,6-bis(N-ethylpiperazine- iminomethyl)-4-methyl-phenolato, has been synthesized and structurally characterized. The X-ray single crystal structure analysis shows that the piperazine moieties assume the expected chair conformation and are protonated. The complex 1 exhibits versatile catalytic activities of biological significance, viz. catecholase, phosphatase, and DNA cleavage activities, etc. The catecholase activity of the complex observed is very dependent on the nature of the solvent. In acetonitrile medium, the complex is inactive to exhibit catecholase activity. On the other hand, in methanol, it catalyzes not only the oxidation of 3,5-ditert-buty !catechol (3,5-DTBC) but also tetrachlorocatechol (TCC), a catechol which is very difficult to oxidize, under aerobic conditions. UV-vis spectroscopic investigation shows that TCC oxidation proceeds through the formation of an intermediate. The intermediate has been characterized by an electron spray ionizaton-mass spectrometry study, which suggests a bidentate rather than a monodentate mode of TCC coordination in that intermediate, and this proposition have been verified by density functional theory calculation. The complex also exhibits phosphatase (with substrate p-nitrophenylphosphate) and DNA cleavage activities. The DNA cleavage activity exhibited by complex 1 most probably proceeds through a hydroxyl radical pathway. The bioactivity study suggests the possible applications of complex 1 as a site specific recognition of DNA and/or as an anticancer agent.
- Chattopadhyay, Tanmay,Mukherjee, Madhupama,Mondal, Arindam,Maiti, Pali,Banerjee, Arpita,Banu, Kazi Sabnam,Bhattacharya, Santanu,Roy, Bappaditya,Chattopadhyay,Mondai, Tapan Kumar,Nethaji, Munirathinam,Zangrando, Ennio,Das, Debasis
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- Designed four-helix bundle catalysts - The engineering of reactive sites for hydrolysis and transesterification reactions of p-nitrophenyl esters
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Four-helix bundle proteins have been designed that catalyze the hydrolysis and transesterification reactions of p-nitrophenyl esters by a cooperative nucleophilic and general acid mechanism. The catalysts consist of two 42-residue peptides that fold into
- Baltzer, Lars,Broo, Kerstin S.,Nilsson, Helena,Nilsson, Jonas
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- Mesoporous zeolites as enzyme carriers: Synthesis, characterization, and application in biocatalysis
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We study the application of hierarchical ZSM-5 zeolites, combining micropores and intracrystalline mesopores, as carriers for lipase enzymes compared with purely microporous ZSM-5 and mesoporous MCM-41. Strategies to improve enzyme immobilization by modif
- Mitchell, Sharon,Pérez-Ramírez, Javier
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- Isotope effects and medium effects on sulfuryl transfer reactions
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Kinetic isotope effects and medium effects have been measured for sulfuryl-transfer reactions of the sulfate ester p-nitrophenyl sulfate (pNPS). The results are compared to those from previous studies of phosphoryl transfer, a reaction with mechanistic similarities. The N-15 and the bridge O-18 isotope effects for the reaction of the pNPS anion are very similar to those of the p-nitrophenyl phosphate (pNPP) dianion. This indicates that in the transition states for both reactions the leaving group bears nearly a full negative charge resulting from a large degree of bond cleavage to the leaving group. The nonbridge O-18 isotope effects support the notion that the sulfuryl group resembles SO3 in the transition state. The reaction of the neutral pNPS species in acid solution is mechanistically similar to the reaction of the pNPP monoanion. In both cases proton transfer from a nonbridge oxygen atom to the leaving group is largely complete in the transition state. Despite their mechanistic similarities, the phosphoryl- and sulfuryl-transfer reactions differ markedly in their response to medium effects. Increasing proportions of the aprotic solvent DMSO to aqueous solutions of pNPP cause dramatic rate accelerations of up to 6 orders of magnitude, but only a 50-fold rate increase is observed for pNPS. Similarly, phosphoryl transfer from the pNPP dianion to tert-amyl alcohol is 9000-fold faster than the aqueous reaction, while the sulfuryl transfer from the pNPS anion is some 40-fold slower. The enthalpic and entropic contributions to these differing medium effects have been measured and compared.
- Hoff,Larsen,Hengge
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- Organoruthenium(II) compounds with pyridyl benzoxazole/benzthiazole moiety: studies on DNA/protein binding and enzyme mimetic activities
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We report herein synthesis and characterization of four new organoruthenium(II) complexes of the type [RuH(CO)(PPh3)2(L1,2)]Cl (1, 3) and [Ru(CO)(Cl)2(AsPh3)(L1,2)] (2, 4) derived from the reaction of [RuHCl(CO)(EPh3)3] (E?=?P or As) with 2-(pyridine-2yl)benzoxazole (L1) and 2-(pyridine-2yl)benzthiazole (L2). Single-crystal X-ray diffraction data of 2 proved octahedral geometry of the complexes with a 1 : 1 ratio between the metal and the coordinated ligands. The binding affinities of 1–4 toward calf-thymus DNA (CT-DNA) and BSA were thoroughly studied by various spectroscopic techniques. Furthermore, the coordination compounds exhibit catecholase-like activities in the aerial oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone and phosphatase-like activities in the hydrolysis of 4-nitrophenyl phosphate to 4-nitrophenolate ion. The kinetic parameters have been determined using Michaelis–Menten approach. The highest kcat values suggested that coordination compounds exhibit higher rates of catalytic efficacy.
- Gomathi, Asaithambi,Vijayan, Paranthaman,Viswanathamurthi, Periasamy,Suresh, Shanmugam,Nandhakumar, Raju,Hashimoto, Takeshi
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- Selective debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate
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A new debenzylation of aromatic benzyl ethers by silica-supported sodium hydrogen sulfate is described. The process proceeds selectively and efficiently in good to excellent yields without affecting sensitive functional groups such as nitro, COOMe, aldehyde, ketone, and tosyl.
- Zhou, Linna,Wang, Wenjing,Zuo, Li,Yao, Shanyan,Wang, Wei,Duan, Wenhu
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- Iron-catalyzed conversion of unactivated aryl halides to phenols in water
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Although iron is low-cost and environmentally friendly, there is no report about iron-catalyzed conversion of unactivated aryl halides to phenols. In this Letter, a new method for the present conversion was developed with iron compounds as the catalyst and water as the solvent. The suggested method allowed a series of unactivated aryl bromides and aryl iodides to be converted into the corresponding substituted phenols in moderate to high yields.
- Ren, Yunlai,Cheng, Lin,Tian, Xinzhe,Zhao, Shuang,Wang, Jianji,Hou, Chaodong
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- Molecular Design of Non-Leloir Furanose-Transferring Enzymes from an α-L-Arabinofuranosidase: A Rationale for the Engineering of Evolved Transglycosylases
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The vast biodiversity of glycoside hydrolases (GHs) constitutes a reservoir of readily available carbohydrate-acting enzymes that employ simple substrates and hold the potential to perform highly stereopecific and regioselective glycosynthetic reactions. However, most GHs preferentially hydrolyze glycosidic bonds and are thus characterized by a hydrolysis/transglycosylation partition in favor of hydrolysis. Unfortunately, current knowledge is insufficient to rationally modify this partition, specifically mutating key molecular determinants to tip the balance toward transglycosylation. In this study, in the absence of precise knowledge concerning the hydrolysis/transglycosylation partition in a hydrolytic GH51 α-L-arabinofuranosidase, we describe how an iterative protein engineering approach has been used to create the first non-Leloir transarabinofuranosylases. In the first step, random mutagenesis yielded a point mutation (R69H) at a position that is highly conserved in clan GH-A. Characterization of R69H revealed that this enzyme displays high transglycosylation activity but severely reduced (61-fold) activity on pNP-α-L-arabinofuranoside. Upon recombination of R69H with other point mutations selected using semirational or in silico approaches, transfer rates close to 100% and transarabinofuranosylation yields of the main (1→2)-linked oligosaccharide product of 80% (vs 11% for the wild-type) were obtained. Combining data presented here with knowledge drawn from the literature, we suggest that the creation of non-Leloir transglycosylases necessarily involves the destabilization of the highly developed transition states that characterize the predominantly hydrolytic exo-acting GHs; this is an efficient way to prevent ubiquitous water molecules from performing the deglycosylation step. (Figure Presented).
- Bissaro, Bastien,Durand, Julien,Biarns, Xevi,Planas, Antoni,Monsan, Pierre,O'Donohue, Michael J.,Faur, Rgis
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- Antibody catalyzed modification of amino acids. Efficient hydrolysis of tyrosine benzoate
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Esterase antibody 522c2, the first example of a catalytic antibody specifically programmed to control the reactivity of functional groups on the side chain of tyrosine, accelerates the hydrolysis of benzoate esters of L-tyrosine and tyrosine-containing dipeptides by a factor of 104 and is moderately active against other benzoate esters.
- Benedetti,Berti,Colombatti,Flego,Gardossi,Linda,Peressini
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- Parallel Behavior in Kinetic and NMR Effects: Secondary Deuterium Isotope Effects on the Alkaline Hydrolysis of Esters
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β-Deuterium secondary kinetic isotope effects (β-D KIEs) on the alkaline hydrolysis of the p-nitrophenyl esters of acetic, propanoic, butanoic, and pentanoic acids in pH 10.70, 0.20 M carbonate buffer at 25 deg C tend to increase with increasing chain length of the esters up to the pentanoate.The β-D KIEs are respectively 0.975 +/- 0.004, 0.960 +/- 0.002, 0.940 +/- 0.001, and 0.948 +/- 0.004.The activation energies of the esterolyses of the isotopically light esters follow a similar pattern, as do the 13C NMR nuclear shieldings in CDCl3 of the isotopically light parent carboxylic acids (20.9, 27.4, 35.9, and 33.8 (ppm)) and 13C NMR one-bond isotope shifts produced by disubstitution of deuterium for hydrogen at the α-carbons of the acids (0.45, 0.55, 0.60, and 0.59 (ppm)).Correlation of nuclear shieldings and isotope shifts is known from previous work.The possibility is considered that all of the kinetics-based and NMR relationships are linked through the operation of a common ground-state feature of the ester and acid alkyl chains.
- Matta, Michael S.,Broadway, Dale E.,Stroot, Michele K.
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- Insights into Catalytic Hydrolysis of Organophosphonates at M-OH Sites of Azolate-Based Metal Organic Frameworks
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Organophosphorus nerve agents, a class of extremely toxic chemical warfare agents (CWAs), have remained a threat to humanity because of their continued use against civilian populations. To date, Zr(IV)-based metal organic framework (MOFs) are the most pre
- Cao, Ran,Chen, Haoyuan,Farha, Omar K.,Islamoglu, Timur,Kirlikovali, Kent O.,Mian, Mohammad Rasel,Snurr, Randall Q.
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- Low ionic liquid concentration in water: A green and simple approach to improve activity and selectivity of lipases
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The activity of several commercial and genetically engineered lipases, already immobilized on octyl-Sepharose, in aqueous solutions containing ionic liquids (ILs) in a molar concentration of 0.01 mol L-1 was investigated. Strong variations in t
- Filice, Marco,Romero, Oscar,Abian, Olga,De Las Rivas, Blanca,Palomo, Jose M.
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- Influence of Water Structure on Solvolysis in Water-in-Oil Microemulsions
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The kinetics of solvolysis of diphenylmethyl chloride, 4-nitrophenyl chloroformate, benzoyl chloride, p-anisoyl chloride, and bis(4-nitrophenyl)carbonate in water/AOT/isooctane microemulsions with various water/surfactant mole ratios W (AOT = sodium bis(2-ethylhexyl)sulfosuccinate) were interpreted by using a pseudophase model in which the substrates are assumed to be distributed between the isooctane and interface phases.The W-dependence of the intrinsic rate constants k for solvolysis at the interface depends on the solvolysis mechanism: for SN1 reactions, k decreased with W, which is attributed to decreasing polarity of the interface; contrariwise, SN2 reactions are accelerated by decreasing W, which is attributed to increasing nucleophilicity of interfacial water.
- Garcia-Rio, L.,Leis, J. R.,Iglesias, E.
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- A Dinuclear Dysprosium Complex as an Air-Stable and Recyclable Catalyst: Applications in the Deacetylation of Carbohydrate, Aliphatic, and Aromatic Molecules
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Two dinuclear DyIII complexes, [Dy2(hmb)2(OTf)2(H2O)4]?HOTf?2 THF (A?HOTf?2 THF) and [Dy2(hmi)3(H2O)2]?2 HOTf (B?2 HOTf), have been synthesized by the reaction of Dy(OTf)3 and the Schiff-base ligands H2hmb (N′-(2-hydroxy-3-methoxybenzylidene)benzohydrazide) or H2hmi ((2-hydroxy-3-methoxyphenyl)methylene isonicotinohydrazine). Disarmed glycosyl trichloroacetimidates can be activated by complex A in the synthesis of 1,2-trans-glycosides with primary and secondary acceptors. This method offers an efficient route to selectively deacetylated monosaccharides and disaccharides in high yields and a green catalyst that can be easily recycled and reused.
- Chiu, Ting-Yu,Chin, Wei,Guo, Jiun-Rung,Liang, Chien-Fu,Lin, Po-Heng
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- Parallel synthesis of alkyl methacrylate latexes for use as catalytic media
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Among thirty-two anion exchange latexes prepared by parallel synthesis, those containing 2-ethylhexyl methacrylate units are the most active as catalytic media for alkaline hydrolysis of p-nitrophenyl alkanecarboxylates.
- Miller, Paul D.,Ford, Warren T.
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- Isolation and characterization of a beta-primeverosidase-like endo-manner beta-glycosidase from Aspergillus fumigatus AP-20.
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A novel beta-glycosidase-producing microorganism was isolated from soil and identified as Aspergillus fumigatus AP-20 based on its taxonomical characteristics. The enzyme was found to be an extracellular protein in the culture of the isolated fungus and w
- Yamamoto, Shigeru,Okada, Masamichi,Usui, Taichi,Sakata, Kanzo
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- Kinetic investigation of the phenolysis of phenyl 4-nitrophenyl and phenyl 2,4-dinitrophenyl carbonates
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The reactions of phenyl 4-nitrophenyl carbonate (PDNPC) and phenyl 2,4-dinitrophenyl carbonate (PDNPC) with a homogeneous series of phenoxide anions are subjected to a kinetic investigation in water at 25.0 °C, ionic strength 0.2 mol dm-3 (KCl). Under phenoxide or total phenol excess over the substrate all these reactions obey pseudo first-order kinetics and are first order in phenoxide. The Bronsted-type plots for the nucleophilic rate constants are linear with slopes 0.61 and 0.49 for the phenolysis of PNPC and PDNPC, respectively. The magnitude of these slopes and the absence of curvature in the Brnsted plot at pKa = 7.1 for the PNPC reactions are consistent with concerted mechanisms (one step) for both reaction series. PDNPC is more reactive than PNPC toward phenoxide nucleophiles; this can be explained by the presence of a second nitro group in PDNPC, which (i) leaves its carbonyl carbon more positively charged than that of PNPC, making the former a better electrophile, and (ii) makes 2,4-dinitrophenoxide a better leaving group than 4-nitrophenoxide. The larger nucleophilic rate coefficients found in this work relative to those obtained in the concerted phenolysis of 4-nitrophenyl and 2,4-dinitrophenyl methyl carbonates is explained by a stronger electron withdrawal from PhO compared to MeO. Comparison of the concerted phenolysis of PNPC with the stepwise reactions of quinuclidines with the same substrate indicates that substitution of a quinuclidino group in a zwitterionic tetrahedral intermediate by a phenoxy group greatly destabilises the intermediate.
- Castro, Enrique A.,Angel, Mauricio,Pavez, Paulina,Santos, Jose G.
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- A strategic approach of enzyme engineering by attribute ranking and enzyme immobilization on zinc oxide nanoparticles to attain thermostability in mesophilic Bacillus subtilis lipase for detergent formulation
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The present study envisaged rationalized protein engineering approach to attain thermostability in a mesophilic Bacillus subtilis lipase. Contributing amino acids for thermostability were analyzed from homologous thermophilic-mesophilic protein dataset th
- Khan, Mohd Faheem,Kundu, Debasree,Hazra, Chinmay,Patra, Sanjukta
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- A Mild Strategy for the Preparation of Phenols via the Ligand-Free Copper-Catalyzed O-Arylation of para -Toluenesulfonic Acid
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A facile and simple ligand-free copper-catalyzed reaction to synthesize substituted phenols is reported. The reaction presumably proceeds via an O-arylsulfonate intermediate that is hydrolyzed to afford good to excellent yields of up to 88%. This protocol provides an alternative to existing reports which use strong hydroxide salts as the direct hydroxylation partner. Demonstrating a wide substrate scope and functional group tolerance, this protocol can also be applied to inexpensive and commercially available carboxylic acids to yield phenols.
- Tan, Bryan Yong-Hao,Teo, Yong-Chua
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- Cellular zwitterionic metabolite analogs simultaneously enhance reaction rate, thermostability, salt tolerance, and substrate specificity of α-glucosidase
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We investigated the structural effects of metabolite analogs derived from a naturally-occurring zwitterionic metabolite, glycine betaine, on the activity of several hydrolases. The initial velocities of the hydrolases were enhanced by the addition of the
- Deguchi, Eisuke,Koumoto, Kazuya
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- Substrate modulation of the activity of an artificial nanoesterase made of peptide-functionalized gold nanoparticles
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Nanozymes with a heart of gold: A functional artificial protein has been prepared by grafting a dodecapeptide onto the surface of gold nanoparticles (see picture). The system catalyzes the hydrolysis of carboxylate esters and features enzyme-like properti
- Pengo, Paolo,Baltzer, Lars,Pasquato, Lucia,Scrimin, Paolo
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- Kinetics and speciation of paraoxon hydrolysis by zinc(II)-azamacrocyclic catalysts
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Four Zn2+-azamacrocyclic complexes were investigated for their ability to catalyze the hydrolysis of the toxic organophosphate (OP) pesticide diethyl paraoxon. Of the four complexes studied, Zn2+-1,5,9-triazacyclododecane (Zn2+-[12]aneN3) was found to be the most effective catalyst with a pseudo-first order reaction rate of k = 6.08 ± 0.23 × 10-4 min-1. Using 31P nuclear magnetic resonance (NMR) spectroscopy, the two products diethyl phosphate (DEP) and ethyl (4-nitrophenyl) phosphate (E4NPP) were identified for both catalyzed and background hydrolysis of paraoxon. Reaction rate and selectivity for formation of the non-toxic DEP were observed to correlate with catalyst pKa. The rate of formation of toxic E4NPP, however, was independent of both the presence and nature of the catalyst. The potential roles of buffer concentration and product inhibition were also investigated. Background hydrolysis at elevated reaction temperatures (50°C) displayed no preference for DEP over that of E4NPP despite substantial differences between the characteristics (i.e., pKa values) of the two leaving groups (ethoxide vs. 4-nitrophenoxide anions). As with previous observations of these types of metal-catalyzed hydrolyses, we invoke the formation of a trigonal bipyramidal-like transition state involving a Zn-coordinated phosphate bond, with the leaving group at the apical position and the incoming HO- anion approaching from the opposite end. Kinetic rates for catalytic hydrolysis display an overwhelming propensity for DEP formation, and suggest the importance of steric restrictions on transition state structure, namely a concerted arrangement of the azamacrocycle in opposition to the bulky 4-nitrophenoxy group.
- Kennedy, Daniel J.,Mayer, Brian P.,Baker, Sarah E.,Valdez, Carlos A.
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- Hydrolysis of organophosphate esters: Phosphotriesterase activity of metallo-ss-lactamase and its functional mimics
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The phosphotriesterase (PTE) activity of a series of binuclear and mononuclear zinc(II) complexes and metallo-β-lactamase (mβl) from Bacillus cereus was studied. The binuclear complex 1, which exhibits good mβl activity, shows poor PTE activity. In contrast, complex 2, a poor mimic of mβl, exhibits much higher activity than 1. The replacement of Cl - ligands by OH- is important for the high PTE activity of complex 2 because this complex does not show any catalytic activi-ty in methanol. The natural enzyme mssl from B. cereus is also found to be an inefficient catalyst in the hydrolysis of phosphotriesters. These observations indicate that the binding of -lactam substrates at the binuclear zinc(II) center is different from that of phosphotriesters. Furthermore, phospho diesters, the products from the hydrolysis of triesters, significantly inhibit the PTE activity of mβl and its functional mimics. Although the mononuclear complexes 3 and 4 exhibited significant mβl activity, these complexes are found to be almost inactive in the hydrolysis of phosphotriesters. These observations indicate that the elimination of phosphodiesters from the reaction site is important for the PTE activity of zinc(II) complexes.
- Tamilselvi,Mugesh, Govindasamy
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- Rationally Designed Double-Shell Dodecahedral Microreactors with Efficient Photoelectron Transfer: N-Doped-C-Encapsulated Ultrafine In2O3 Nanoparticles
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It is desirable but challenging to design efficient micro-/nanoreactors for chemical reactions. In this study, we have fabricated mesoporous double-shelled hollow microreactors composed of N-doped-C-coated ultrafine In2O3 nanoparticles [N-C/In2O3 HD (hollow dodecahedron)] by the thermolysis of a dodecahedral In-based framework in Ar atmosphere. The obtained N-C/In2O3 HD exhibited excellent activity in the photocatalytic oxidative hydroxylation of a series of arylboronic acid substrates. This property can be attributed to its enhanced optical absorption and efficient separation of photo-generated electron–hole pairs, imparted by the unique structure and uniformly coated N-doped C layers. Furthermore, we found O2.? to be the critical active species in the process of photocatalytic oxidative hydroxylation of arylboronic acids, and the formation mechanism of this radical is also proposed. Theoretical calculations further confirmed that the N-doped C layer serves as an electron acceptor and revealed the microscopic charge-carrier migration path through the In2O3/N-doped graphite interfaces. Thus, photo-generated electrons from hybrid states of In2O3, composed of In 5s and 2p orbitals, are transferred into the hybrid states of N-doped graphite, composed of C 2p and N 2p orbitals. The present study may be helpful for understanding and designing carbon-based micro-/nanoreactors for photocatalytic reactions, and may also be useful for investigating related micro-/nanoreactors.
- Sun, Liming,Li, Rong,Zhan, Wenwen,Wang, Fan,Zhuang, Yuan,Wang, Xiaojun,Han, Xiguang
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- Phenol transformation photosensitised by quinoid compounds
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The phototransformation of phenol in aqueous solution was studied with different quinoid compounds, which are usually detected on atmospheric particulate matter: 2-ethylanthraquinone (EtAQ), benzanthracene-7,12-dione (BAD), 5,12-naphthacenequinone (NQ), 9,10-anthraquinone (AQ), and 2,6-dihydroxyanthraquinone (DAQ). All the studied quinones were able to sensitise the phototransformation of phenol. Under blue-light irradiation the approximated, polychromatic quantum yields for phenol photodegradation were in the order AQ > BAD > EtAQ > NQ > DAQ. Quantum mechanical calculations showed that AQ and DAQ have a very different spin distribution in the triplet state (largely located on the carbonyl oxygen and delocalised over the aromatic ring, respectively) that could account for the difference in reactivity. The spin distribution of EtAQ is similar to that of AQ. Under simulated sunlight, EtAQ induced the highest rate of phenol degradation. Radiation-excited EtAQ would oxidise both ground-state EtAQ and phenol; a kinetic model that excludes the OH radical and singlet oxygen as reactive species is supported by the experimental data. Quinones were also able to oxidise nitrite to nitrogen dioxide, thereby inducing phenol nitration. Such a process is a potential source of nitrogen dioxide and nitrophenols in the atmospheric aerosols. the Owner Societies.
- Maurino, Valter,Bedini, Andrea,Borghesi, Daniele,Vione, Davide,Minero, Claudio
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- Use of MoO2Cl2(DMF)2 as a precursor for molybdate promoted hydrolysis of phosphoester bonds
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Phosphoester bond cleavage of para-nitrophenylphosphate (pNPP), a commonly used model substrate, is accelerated by using the complex MoO2Cl 2(DMF)2 (1) (DMF = dimethylformamide) as a hydrolysis promoting agent, even when c
- Tome, Catia M.,Oliveira, M. Conceicao,Pillinger, Martyn,Goncalves, Isabel S.,Abrantes, Marta
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- Lithium pipecolinate as a facile and efficient ligand for copper-catalyzed hydroxylation of aryl halides in water
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Direct hydroxylation of a wide scope of aryl halides was catalyzed by a combination of CuI and lithium pipecolinate in water with yields up to 92%.
- Jing, Linhai,Wei, Jiangtao,Zhou, Li,Huang, Zhiyong,Li, Zhengkai,Zhou, Xiangge
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- Enzyme shielding in an enzyme-thin and soft organosilica layer
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The fragile nature of most enzymes is a major hindrance to their use in industrial processes. Herein, we describe a synthetic chemical strategy to produce hybrid organic/inorganic nanobiocatalysts; it exploits the self-assembly of silane building blocks at the surface of enzymes to grow an organosilica layer, of controlled thickness, that fully shields the enzyme. Remarkably, the enzyme triggers a rearrangement of this organosilica layer into a significantly soft structure. We demonstrate that this change in stiffness correlates with the biocatalytic turnover rate, and that the organosilica layer shields the enzyme in a soft environment with a markedly enhanced resistance to denaturing stresses. Important soft skills: Hybrid organic/inorganic nanobiocatalysts were created by the immobilization of enzymes on amino-modified silica nanoparticles and subsequent self-assembly and polycondensation of silane building blocks at the surface of the enzymes. The soft environment of the organosilica layer shielded the enzymes from denaturing stresses; however, the enzymes retained their conformational freedom and thus their catalytic activity (see picture).
- Correro, M. Rita,Moridi, Negar,Schützinger, Hansj?rg,Sykora, Sabine,Ammann, Erik M.,Peters, E. Henrik,Dudal, Yves,Corvini, Philippe F.-X.,Shahgaldian, Patrick
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- Nylon–MOF Composites through Postsynthetic Polymerization
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Hybridization of metal–organic frameworks (MOFs) and polymers into composites yields materials that display the exceptional properties of MOFs with the robustness of polymers. However, the realization of MOF–polymer composites requires efficient dispersion and interactions of MOF particles with polymer matrices, which remains a significant challenge. Herein, we report a simple, scalable, bench-top approach to covalently tethered nylon–MOF polymer composite materials through an interfacial polymerization technique. The copolymerization of a modified UiO-66-NH2 MOF with a growing polyamide fiber (PA-66) during an interfacial polymerization gave hybrid materials with up to around 29 weight percent MOF. The covalent hybrid material demonstrated nearly an order of magnitude higher catalytic activity for the breakdown of a chemical warfare simulant (dimethyl-4-nitrophenyl phosphate, DMNP) compared to MOFs that are non-covalently, physically entrapped in nylon, thus highlighting the importance of MOF–polymer hybridization.
- Kalaj, Mark,Denny, Michael S.,Bentz, Kyle C.,Palomba, Joseph M.,Cohen, Seth M.
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- Mesoporous Core-Shell Nanostructures Bridging Metal and Biocatalyst for Highly Efficient Cascade Reactions
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Mesoporous core-shell structured nanocatalysts with a PdPt bimetallic core and enzyme-immobilized polydopamine (PDA) shell were designed, in which the PDA shell worked as a barrier to position the bimetallic core and enzyme in separated locations. The accessible mesoporous structures of both the core and shell significantly facilitate mass transfer and catalyst utilization, improving the synergistic catalytic abilities in cascade reactions. The obtained bifunctional nanocatalysts enabled efficient two-step one-pot cascade reactions of different types: dynamic kinetic resolution of primary amines in organic solvent with high yield and enantioselectivity (up to 99% yield and 98% ee) and degradation of organophosphate nerve agent in aqueous solution with high rate constant and turnover frequency number values (0.8 min-1 and 20 min-1, respectively).
- Gao, Jing,Gao, Shiqi,Jiang, Yanjun,Liu, Yunting,Ma, Li,Wang, Zihan
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- The catalytic serine of meta-cleavage product hydrolases is activated differently for C-O bond cleavage than for C-C bond cleavage
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meta-Cleavage product (MCP) hydrolases catalyze C-C bond fission in the aerobic catabolism of aromatic compounds by bacteria. These enzymes utilize a Ser-His-Asp triad to catalyze hydrolysis via an acyl-enzyme intermediate. BphD, which catalyzes the hydrolysis of 2-hydroxy-6-oxo-6-phenylhexa-2,4-dienoic acid (HOPDA) in biphenyl degradation, catalyzed the hydrolysis of an ester analogue, p-nitrophenyl benzoate (pNPB), with a kcat value (6.3 ± 0.5 s-1) similar to that of HOPDA (6.5 ± 0.5 s-1). Consistent with the breakdown of a shared intermediate, product analyses revealed that BphD catalyzed the methanolysis of both HOPDA and pNPB, partitioning the products to benzoic acid and methyl benzoate in similar ratios. Turnover of HOPDA was accelerated up to 4-fold in the presence of short, primary alcohols (methanol > ethanol > n-propanol), suggesting that deacylation is rate-limiting during catalysis. In the steady-state hydrolysis of HOPDA, kcat/Km values were independent of methanol concentration, while both kcat and Km values increased with methanol concentration. This result was consistent with a simple model of nucleophilic catalysis. Although the enzyme could not be saturated with pNPB at methanol concentrations of >250 mM, kobs values from the steady-state turnover of pNPB at low methanol concentrations were also consistent with a nucleophilic mechanism of catalysis. Finally, transient-state kinetic analysis of pNPB hydrolysis by BphD variants established that substitution of the catalytic His reduced the rate of acylation by more than 3 orders of magnitude. This suggests that for pNPB hydrolysis, the serine nucleophile is activated by the His-Asp dyad. In contrast, rapid acylation of the H265Q variant during C-C bond cleavage suggests that the serinate forms via a substrate-assisted mechanism. Overall, the data indicate that ester hydrolysis proceeds via the same acyl-enzyme intermediate as that of the physiological substrate but that the serine nucleophile is activated via a different mechanism.
- Ruzzini, Antonio C.,Horsman, Geoff P.,Eltis, Lindsay D.
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- The mechanism by which 4-hydroxy-2,2,6,6-tetramethylpiperidene-1-oxyl (tempol) diverts peroxynitrite decomposition from nitrating to nitrosating species
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Tempol is a stable nitroxide radical that has been shown to protect laboratory animals from the injury associated with conditions of oxidative and nitrosoactive stress. Tempol's protective mechanisms against reactive oxygen species have been extensively studied, but its interactions with reactive nitrogen species remain little explored. Recently, it has been shown that tempol is a potent inhibitor of peroxynitrite-mediated phenol nitration while it increases phenol nitrosation by a complex mechanism [Carrol et al. (2000) Chem. Res. Toxicol. 13, 294]. To obtain further mechanistic insights, we reexamined the interaction of peroxynitrite with tempol in the absence and presence of carbon dioxide. Stopped-flow kinetic studies confirmed that tempol does not react directly with peroxynitrite but levels off the amount of oxygen (monitored with an oxygen electrode) and nitrite (monitored by chemiluminescence) produced from peroxynitrite in the presence and absence of carbon dioxide to about 30% and 70% of the initial oxidant concentration at pH 5.4, 6.4, and 7.4. Tempol inhibited phenol nitration while increasing the amounts of 4-nitrosophenol, that attained yields close to 30% of the peroxynitrite in the presence of carbon dioxide at pH 7.4. Fast-flow EPR experiments showed detectable changes in the instantaneous tempol concentration (maximum of 15%) only in the presence of carbon dioxide. Under these conditions, the instantaneous concentration of the carbonate radical anion was reduced by tempol in a concentration-dependent manner. The results indicate that tempol is oxidized by peroxynitrite-derived radicals (·OH and CO3·-, in the absence and presence of carbon dioxide, respectively) to the oxoammonium cation which, in turn, is reduced back to tempol while oxidizing peroxynitrite to oxygen and nitric oxide. The latter reacts rapidly with peroxynitrite-derived nitrogen dioxide to produce the nitrosating species, dinitrogen trioxide. Overall, the results support a role for peroxynitrite and its derived radicals in the tissue pathology associated with inflammatory conditions.
- Bonini, Marcelo G.,Mason, Ronald P.,Augusto, Ohara
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- Solvent effects on reactions of hydroxide and oximate ions with phosphorus(V) esters
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Second-order rate constants of reactions of OH-, 2,3-butanedionemonooximate and 2-hydroxybenzaldoximate ions with aryl phosphate, phosphinate and thioarylphosphinate esters go through minima with decreasing water content of aqueous acetonitrile, tert-butyl alcohol and N-methyl-2-pyrrolidone. For reactions in H2O-MeCN the solvent effects are analyzed in terms of activity coefficients of the anionic nucleophiles and transition states. In the drier solvents partial desolvation of the nucleophiles increases rates. Nucleophilicities of several oximates and inorganic anions are compared in water.
- Bunton, Clifford A.,Gillitt, Nicholas D.,Kumar, Anurag
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- Inhibition of Yersinia protein tyrosine phosphatase by phosphonate derivatives of calixarenes
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Inhibition of Yersinia protein tyrosine phosphatase by calix[4]arene mono-, bis-, and tetrakis(methylenebisphosphonic) acids as well as calix[4]arene and thiacalix[4]arene tetrakis(methylphosphonic) acids have been investigated. The kinetic studies reveal
- Vovk, Andriy I.,Kononets, Lyudmyla A.,Tanchuk, Vsevolod Yu.,Cherenok, Sergiy O.,Drapailo, Andriy B.,Kalchenko, Vitaly I.,Kukhar, Valery P.
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- Motif-guided identification of a glycoside hydrolase family 1 α-L-arabinofuranosidase in bifidobacterium adolescentis
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Members of glycoside hydrolase family 1 (GH1) cleave glycosidic linkages with a variety of physiological roles. Here we report a unique GH1 member encoded in the genome of Bifidobacterium adolescentis ATCC 15703. This enzyme, BAD0156, was identified from over 2,000 GH1 sequences accumulated in a database by a genome mining approach based on a motif sequence. A recombinant BAD0156 protein was characterized to confirm that this enzyme alone specifically hydrolyzes p-nitrophenyl-α-L-arabinofuranoside among the 24 pnitrophenyl- glycosides examined. Among natural glycosides, α-1,5-linked arabino-oligosaccharides served as substrates, but arabinan, debranched arabinan, arabinoxylan, and arabinogalactan did not. A time course analysis of arabino-oligosaccharide hydrolysis indicated that BAD0156 is an exo-acting enzyme. These results suggest that BAD0156 is an α-L-arabinofuranosidase. This is the first report of a GH1 enzyme that acts specifically on arabinosides, providing information on GH1 substrate specificity.
- Suzuki, Hirokazu,Murakami, Ayano,Yoshida, Ken-Ichi
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- Functional characterization of salt-tolerant microbial esterase WDEst17 and its use in the generation of optically pure ethyl (R)-3-hydroxybutyrate
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The two enantiomers of ethyl 3-hydroxybutyrate are important intermediates for the synthesis of a great variety of valuable chiral drugs. The preparation of chiral drug intermediates through kinetic resolution reactions catalyzed by esterases/lipases has been demonstrated to be an efficient and environmentally friendly method. We previously functionally characterized microbial esterase PHE21 and used PHE21 as a biocatalyst to generate optically pure ethyl (S)-3-hydroxybutyrate. Herein, we also functionally characterized one novel salt-tolerant microbial esterase WDEst17 from the genome of Dactylosporangium aurantiacum subsp. Hamdenensis NRRL 18085. Esterase WDEst17 was further developed as an efficient biocatalyst to generate (R)-3-hydroxybutyrate, an important chiral drug intermediate, with the enantiomeric excess being 99% and the conversion rate being 65.05%, respectively, after process optimization. Notably, the enantio-selectivity of esterase WDEst17 was opposite than that of esterase PHE21. The identification of esterases WDEst17 and PHE21 through genome mining of microorganisms provides useful biocatalysts for the preparation of valuable chiral drug intermediates.
- Wang, Yilong,Xu, Yongkai,Zhang, Yun,Sun, Aijun,Hu, Yunfeng
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- Guanidine-based polymer brushes grafted onto silica nanoparticles as efficient artificial phosphodiesterases
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Polymer brushes grafted to the surface of silica nanoparticles were fabricated by atom-transfer radical polymerization (ATRP) and investigated as catalysts in the cleavage of phosphodiesters. The surfaces of silica nanoparticles were functionalized with an ATRP initiator. Surface-initiated ATRP reactions, in varying proportions, of a methacrylate moiety functionalized with a phenylguanidine moiety and an inert hydrophilic methacrylate species afforded hybrid nanoparticles that were characterized with potentiometric titrations, thermogravimetric analysis, and SEM. The activity of the hybrid nanoparticles was tested in the transesterification of the RNA model compound 2-hydroxypropyl para-nitrophenylphosphate (HPNP) and diribonucleoside monophosphates. A high catalytic efficiency and a remarkable effective molarity, thus overcoming the effective molarities previously observed for comparable systems, indicate the existence of an effective cooperation of the guanidine/guanidinium units and a high level of preorganization in the nanostructure. The investigated system also exhibits a marked and unprecedented selectivity for the diribonucleoside sequence CpA. The results presented open up the way for a novel and straightforward strategy for the preparation of supramolecular catalysts.
- Savelli, Claudia,Salvio, Riccardo
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- β-D-GLUCOSIDASE-CATALYSED TRANSFER OF THE GLYCOSYL GROUP FROM ARYL β-D-GLUCO- AND β-D-XYLO-PYRANOSIDES TO PHENOLS
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The effect of phenols on the hydrolysis of substituted phenyl β-D-gluco- and β-D-xylo-pyranosides by β-D-glucosidase from Stachybotrys atra has been investigated.Depending on the glycon part of the substrate and on the phenol substituent, the hydrolysis is either inhibited or activated.With aryl β-D-glucopyranosides, such transfer does not occur when phenols are used as acceptors, but it does occur with anilines.A two-steps mechanism, in which the first step is partially reversible, is proposed to explain these observations.A qualitative analysis of the various factors determing the overall effect of the phenol is given.
- Aerts, Guido M.,Opstal, Omer Van,Bruyne, Clement K. De
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- Participation of an Extended p-Oxo Ketene Intermediate in the Dissociative Alkaline Hydrolysis of Aryl 4-Hydroxycinnamates
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The alkaline hydrolysis of 4-hydroxycinnamate esters of acidic phenols follows an E1cB mechanism and involves the participation of an "extended" p-oxo ketene intermediate.The apparent bimolecular rate constant (kaKa/Kw) for the hydrolysis of the 2,4-dinitrophenyl ester is some 2500-fold larger than that determined from the Hammett relationship for the BAc2 alkaline hydrolysis of substituted 2,4-dinitrophenyl cinnamates.The positive value of entropy of activation for the hydrolysis of 2,4-dinitrophenyl 4'-hydroxycinnamate and trapping experiments with nitrogen nucleophiles are consistent with the dissociative pathway.A change from a E1cB to a BAc2 mechanism is expected for esters with leaving groups having pKa higher than ca. 6.7.The higher E1cB reactivity of 2,4-dinitrophenyl 4'-hydroxycinnamate compared to that of the corresponding 4'-hydroxybenzoate is due to the vinylene group that further favors the dissociative route, probably increasing the stability of the unsaturated intermediate.
- Cevasco, Giorgio,Thea, Sergio
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- Evolution of metal complex-catalysts by dynamic templating with transition state analogs
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The elicitation of hydrolytic catalysts from a dynamic library of imine-zinc(II) complexes (and their precursor aldehydes and amines) via templating with pro-transition state analogs (pro-TSA) is described. pro-TSA (2-pyridyl)phosphonate 2 amplifies a ben
- Matsumoto, Masaomi,Estes, Deven,Nicholas, Kenneth M.
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- Isoenzymes of pig-liver esterase reveal striking differences in enantioselectivities
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(Graph Presented) An esterase toolbox: A set of isoenzymes of pig liver esterases (PLE) is identified, cloned, and overexpressed in E. coli. They show striking differences in enantioselectivity and enantiopreference in the kinetic resolution of acetates o
- Hummel, Anke,Bruesehaber, Elke,Boettcher, Dominique,Trauthwein, Harald,Doderer, Kai,Bornscheuer, Uwe T.
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- Characterization of alkaline phosphatase PhoK from Sphingomonas sp. BSAR-1 for phosphate monoester synthesis and hydrolysis
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The biocatalytic activity of a so far underexploited alkaline phosphatase, PhoK from Sphingomonas sp. BSAR-1, was extensively studied in transphosphorylation and hydrolysis reactions. The use of high-energy phosphate donors and oligophosphates as suitable
- Lukesch, Michael,Tasnádi, Gábor,Ditrich, Klaus,Hall, Mélanie,Faber, Kurt
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- A Mechanistic Study on the Non-enzymatic Hydrolysis of Kdn Glycosides
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Sialic acids are biologically important carbohydrates that are prevalent throughout nature. We are interested in their intrinsic reactivity in aqueous solution and how such reactivity affects the design of substrates for investigation of enzymes that process these sugars. To probe the reactivity differences between two sialic acid family members N-acetylneuraminic acid and Kdn we measured the rate constants for hydrolysis of 4-nitrophenyl 3-deoxy-d-glycero-α-d-galacto-non-2-ulosonide in aqueous solution. The kinetic data is consistent with glycosidic C?O bond cleavage occurring via four mechanistic pathways, and these are: (i) hydronium ion-catalyzed hydrolysis of the neutral sugar; (ii) hydronium ion-catalyzed hydrolysis of the glycosidic carboxylate; (iii) water-catalyzed hydrolysis of the anionic glycoside; and (iv) base-promoted reaction of the anionic glycoside. To study the effects of C-5 substitution on the Kdn glycoside we made 4-nitrophenyl 5-O-methyl-α-Kdn glycoside and determined its rate constants for hydrolysis. All hydrolytic rate constants for both Kdn glycosides were larger than those reported for the parent N-acetyl-α-neuraminide. The water-catalyzed reaction (pathway iii) exhibited a βlg value of ?1.3±0.1. We conclude that the larger rate constants associated with C5-oxygen containing sialosides results from less steric congestion at the hydrolytic transition states than for the parent C-5 acetamido glycoside.
- Nejatie, Ali,Colombo, Cinzia,Hakak-Zargar, Benyamin,Bennet, Andrew J.
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- A highly photosensitive covalent organic framework with pyrene skeleton as metal-free catalyst for arylboronic acid hydroxylation
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Covalent organic frameworks (COFs) have been widely utilized in metal-free photocatalytic synthesis base on their excellent properties such as super conjugation, porosity and stability. In this work, we synthesized a new COF material using 1,3,6,8-Tetrakis (p-formylphenyl)pyrene (TFPPy) and 2,2′-Dimethylbenzidine (DMBZ) as basic units through Schiff base condensation reaction. The new COF (TF-DM COF) was applied as metal-free catalyst for hydroxylation of arylboronic acids. The results indicated that the extended π conjugation of COFs enhanced the absorption of visible light, and the large porosity (BET surface area: 113.782 m2g?1) accelerated the reaction rate. Good recyclability enables it with multiple applications, which result in a great reducing of the cost. This study reports that TF-DM COF has a broad application prospect as a new generation of metal-free photocatalysts for organic conversions.
- Chen, Ying,Huo, Jianqiang,Zhang, Yubao
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- Nanostructured manganese oxides as highly active catalysts for enhanced hydrolysis of bis(4-nitrophenyl)phosphate and catalytic decomposition of methanol
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Manganese oxide-based (MnOx) catalysts have received increasing attention due to their low cost, low toxicity, and the ability to degrade organic molecules under mild conditions. In this work, several nanostructured MnOx-based cataly
- ??astny, Martin,Issa, Gloria,Popelková, Daniela,Ederer, Jakub,Kormunda, Martin,K?í?enecká, Sylvie,Henych, Ji?í
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p. 1766 - 1779
(2021/03/29)
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- Phosphoester hydrolysis promoted by quinoline functionalized Ni(II) and Zn(II) complexes
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A quinoline functionalized nitrogen-based bidentate ligand (L) was synthesized and used for the preparation of mononuclear Ni(II) and Zn(II) complexes which differ only by the halide ion attached to the respective metal center. All complexes of this serie
- Junaid, Qazi Mohammad,Sureshbabu, Popuri,Sabiah, Shahulhameed
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p. 1550 - 1562
(2021/04/29)
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- Biochemical and biophysical characterisation of a small purified lipase from Rhizopus oryzae ZAC3
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The characteristics of a purified lipase from Rhizopus oryzae ZAC3 (RoL-ZAC3) were investigated. RoL-ZAC3, a 15.8 kDa protein, which was optimally active at pH 8 and 55 °C had a half-life of 126 min at 60 °C. The kinetic parameters using p-nitrophenylbuty
- Ayinla, Zainab A.,Ademakinwa, Adedeji N.,Gross, Richard A.,Agboola, Femi K.
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- A novel organic-solvent and detergent resistant esterase from Bacillus sp. isolated from Bazangan Lake
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This study reports biochemical features of a novel esterase of Bacillus sp. HP 96 isolated from Bazangan Lake in Iran. The optimum pH and temperature for 53.4 kDa-purified esterase were 8 and 40 °C, respectively. The HPLC technique was used to examine the
- Pasban-Ziyarat, Fatemeh,Mehrzad, Jamshid,Asoodeh, Ahmad,Deiminiat, Behjat,Motavalizadehkakhky, Alireza
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- Self-Assembled Peptide Nano-Superstructure towards Enzyme Mimicking Hydrolysis
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The structural arrangement of amino acid residues in native enzymes underlies their remarkable catalytic properties, thus providing a notable point of reference for designing potent yet simple biomimetic catalysts. Herein, we describe a minimalistic appro
- Chen, Yu,Dong, Hao,Gazit, Ehud,Haimov, Elvira,Ju, Meiting,Makam, Pandeeswar,Orr, Asuka A.,Redko, Boris,Rencus-Lazar, Sigal,Shimon, Linda J. W.,Tamamis, Phanourios,Wang, Yannan,Yang, Yuqin
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supporting information
p. 17164 - 17170
(2021/06/27)
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- Fine-Tuning the Micro-Environment to Optimize the Catalytic Activity of Enzymes Immobilized in Multivariate Metal-Organic Frameworks
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The artificial engineering of an enzyme’s structural conformation to enhance its activity is highly desired and challenging. Anisotropic reticular chemistry, best illustrated in the case of multivariate metal-organic frameworks (MTV-MOFs), provides a platform to modify a MOF’s pore and inner-surface with functionality variations on frameworks to optimize the interior environment and to enhance the specifically targeted property. In this study, we altered the functionality and ratio of linkers in zeolitic imidazolate frameworks (ZIFs), a subclass of MOFs, with the MTV approach to demonstrate a strategy that allows us to optimize the activity of the encapsulated enzyme by continuously tuning the framework-enzyme interaction through the hydrophilicity change in the pores’ microenvironment. To systematically study this interaction, we developed the component-adjustment-ternary plot (CAT) method to approach the optimal activity of the encapsulated enzyme BCL and revealed a nonlinear correlation, first incremental and then decremental, between the BCL activity and the hydrophilic linker’ ratios in MTV-ZIF-8. These findings indicated there is a spatial arrangement of functional groups along the three-dimensional space across the ZIF-8 crystal with a unique sequence that could change the enzyme structure between closed-lid and open-lid conformations. These conformation changes were confirmed by FTIR spectra and fluorescence studies. The optimized BCL@ZIF-8 is not only thermally and chemically more stable than free BCL in solution, but also doubles the catalytic reactivity in the kinetic resolution reaction with 99%eeof the products.
- Li, Yi-Ming,Yuan, Jian,Ren, Hao,Ji, Chun-Yan,Tao, Yu,Wu, Yahui,Chou, Lien-Yang,Zhang, Yue-Biao,Cheng, Lin
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supporting information
p. 15378 - 15390
(2021/09/18)
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- Exploring the catalytic mechanism of a novel β-glucosidase BGL0224 from Oenococcus oeni SD-2a: Kinetics, spectroscopic and molecular simulation
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The β-glucosidase derived from microorganisms has attracted worldwide interest for their industrial applications, but studies on β-glucosidases from Oenococcus oeni are rare. In this paper, catalytic mechanism of a novel β-glucosidase BGL0224 of Oenococcu
- Zhang, Jie,Zhao, Ning,Xu, Junnan,Qi, Yiman,Wei, Xinyuan,Fan, Mingtao
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- A copper nitride catalyst for the efficient hydroxylation of aryl halides under ligand-free conditions
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Copper nitride (Cu3N) was used as a heterogeneous catalyst for the hydroxylation of aryl halides under ligand-free conditions. The cubic Cu3N nanoparticles showed high catalytic activity, comparable to those of conventional Cu catalysts with nitrogen ligands, demonstrating that the nitrogen atoms in Cu3N act as functional ligands that promote hydroxylation.
- Mitsudome, Takato,Mizugaki, Tomoo,Xu, Hang,Yamaguchi, Sho
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supporting information
p. 6593 - 6597
(2021/08/10)
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- Electrochemical-induced hydroxylation of aryl halides in the presence of Et3N in water
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A thorough study of mild and environmentally friendly electrochemical-induced hydroxylation of aryl halides without a catalyst is presented. The best protocol consists of hydroxylation of different aryl iodides and aryl bromides by water solution in the presence of Et3N under air, affording the target phenols in good isolated yields. Moreover, aryl chlorides were successfully employed as substrates. This methodology also provides a direct pathway for the formation of deoxyphomalone, which displayed a significant anti-proliferation effect.
- Ke, Fang,Lin, Chen,Lin, Mei,Long, Hua,Wu, Mei,Yang, Li,Zhuang, Qinglong
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supporting information
p. 6417 - 6421
(2021/08/03)
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- MIL-101(Cr) with incorporated polypyridine zinc complexes for efficient degradation of a nerve agent simulant: spatial isolation of active sites promoting catalysis
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Development of an efficient catalyst for degradation of organophosphorus toxicants is highly desirable. Herein, an MIL-101(Cr)LZn catalyst was fabricated by incorporating polypyridine zinc complexes into a MOF to achieve the spatial isolation of active si
- Zhang, Kai,Cao, Xingyun,Zhang, Zhiyan,Cheng, Yong,Zhou, Ying-Hua
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supporting information
p. 1995 - 2000
(2021/02/26)
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- Paraoxonase Mimic by a Nanoreactor Aggregate Containing Benzimidazolium Calix and l-Histidine: Demonstration of the Acetylcholine Esterase Activity
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An anion-mediated preorganization approach was used to design and synthesize the benzimidazolium-based calix compound R1?2 ClO4?. X-ray crystallography analysis revealed that the hydrogen-bonding interactions between the benzimidazol
- Singh, Amanpreet,Saini, Sanjeev,Mayank,Kaur, Navneet,Singh, Ajnesh,Singh, Narinder,Jang, Doo Ok
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p. 5737 - 5744
(2021/03/08)
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- Degradation of Organophosphates Promoted by 1,2,4-Triazole Anion: Exploring Scaffolds for Efficient Catalytic Systems
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Organophosphate (OP) pesticides are responsible for numerous human deaths every year. Nucleophilic substitution is an important method to mitigate the toxicity of obsolete stocks of OPs. Herein, the degradation of O,O-diethyl-2,4-dinitrophenyl phosphate (DEDNPP) and pesticide diethyl-4-nitrophenyl phosphate (Paraoxon) promoted by 1,2,4-triazole (TAZ) was investigated by means of kinetic studies, nuclear magnetic resonance (NMR) analyses, and theoretical calculations. Results showed fast degradation of OPs is promoted by the anionic form of the nucleophile (TAZ(-)) in pH > 8.5 (optimal at pH = 11). Rate enhancements of 106 and 105-fold in relation to neutral hydrolysis of DEDNPP and Paraoxon were observed, respectively, consistent with alpha-nucleophiles reactivity. TAZ(-) regioselectively promotes the degradation of DEDNPP via P-O bond break, forming a quickly hydrolyzable phosphorylated intermediate, regenerating the nucleophile. Calculations using M06-2X/6-311++G(d,p) level of theory revealed that the equivalent nitrogen atoms of TAZ(-) are the main nucleophilic center of the molecule. This study expands the knowledge on the reactivity of iminic compounds as detoxificant agents of OPs, indicating the efficiency and selectivity of TAZ(-) in aqueous medium, encouraging the design of novel TAZ-based catalysts.
- Fernandes, Juliano M.,Soek, Rafael N.,Do Nascimento, Thalita C.,Menezes, Leociley R. A.,Sassaki, Guilherme L.,Campos, Renan B.
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supporting information
p. 4027 - 4034
(2021/03/01)
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- Role of Zr6Metal Nodes in Zr-Based Metal-Organic Frameworks for Catalytic Detoxification of Pesticides
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Pesticides are chemicals widely used for agricultural industry, despite their negative impact on health and environment. Although various methods have been developed for pesticide degradation to remedy such adverse effects, conventional materials often ta
- Nam, Dongsik,Kim, Yeongjin,Kim, Miyeon,Nam, Joohan,Kim, Seonghoon,Jin, Eunji,Lee, Chang Yeon,Choe, Wonyoung
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supporting information
p. 10249 - 10256
(2021/06/27)
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- Tetraacuo-bis-(N,N-dimethylacetamide-O)magnesium(II) chloride dihydrate. An option to improve magnesium effect on phosphatase stimulation and albumin binding
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Magnesium compounds became relevant since the discovery that this element is essential and its deficiency causes several diseases. From these findings, magnesium supplementation became a pharmacologically important issue that prompted the search for new d
- Echeverría, Gustavo A.,Ferrer, Evelina G.,Franca, Carlos A.,Martini, Nancy,Parente, Juliana E.,Piro, Oscar E.,Restrepo-Guerrero, Gonzalo,Williams, Patricia A. M.
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- Design and Synthesis of Supramolecular Phosphatases Formed from a Bis(Zn2+-Cyclen) Complex, Barbital-Crown-K+ Conjugate and Cu2+ for the Catalytic Hydrolysis of Phosphate Monoester
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The development of artificial mimics of natural enzymes such as hydrolases and phosphatases is one of the great challenges in bioorganic and bioinorganic chemistry and related sciences. Supramolecular strategies are one of the useful methods to construct
- Rahman, Akib Bin,Okamoto, Hirokazu,Miyazawa, Yuya,Aoki, Shin
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p. 1213 - 1223
(2021/02/01)
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- SUPRAMOLECULAR GEL SUPPORTED ON OPEN-CELL POLYMER FOAM
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The present invention relates to a polymer foam, said polymer foam comprising pores forming an open-cell polymer foam, said polymer foam comprising a supramolecular gel inside pores, and said polymer foam comprising at least one enzyme. The present invention relates to a supramolecular gel; its preparation and its applications, notably in chemical synthesis and kinetic resolution, in particular of organic compounds. The present invention also relates to flow chemistry.
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Page/Page column 20
(2021/03/19)
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- Bioinspired Phosphatase-like Mimic Built from the Self-Assembly of de Novo Designed Helical Short Peptides
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Enzymes play vital roles in catalyzing biochemical reactions with high activity and selectivity, which is largely attributed to the delicately organized structure and groups at catalytic domains. Reconstruction of the enzymatic catalytic domains in artifi
- He, Zhimin,Qi, Wei,Su, Rongxin,Wang, Mengfan,Wang, Yutong,Yang, Lijun,Zhang, Jiaxing
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p. 5839 - 5849
(2021/05/31)
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- Biochemical characterization of a recombinant acid phosphatase from Acinetobacter baumannii
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Genomic sequence analysis of Acinetobacter baumannii revealed the presence of a putative Acid Phosphatase (AcpA; EC 3.1.3.2). A plasmid construct was made, and recombinant protein (rAcpA) was expressed in E. coli. PAGE analysis (carried out under denaturing/ reducing conditions) of nickel-affinity purified protein revealed the presence of a nearhomogeneous band of approximately 37 kDa. The identity of the 37 kDa species was verified as rAcpA by proteomic analysis with a molecular mass of 34.6 kDa from the deduced sequence. The dependence of substrate hydrolysis on pH was broad with an optimum observed at 6.0. Kinetic analysis revealed relatively high affinity for PNPP (Km = 90 μM) with Vmax, kcat, and Kcat/Km values of 19.2 pmoles s-1, 4.80 s-1(calculated on the basis of 37 kDa), and 5.30 × 104 M-1s-1, respectively. Sensitivity to a variety of reagents, i.e., detergents, reducing, and chelating agents as well as classic acid phosphatase inhibitors was examined in addition to assessment of hydrolysis of a number of phosphorylated compounds. Removal of phosphate from different phosphorylated compounds is supportive of broad, i.e., 'nonspecific' substrate specificity; although, the enzyme appears to prefer phosphotyrosine and/or peptides containing phosphotyrosine in comparison to serine and threonine. Examination of the primary sequence indicated the absence of signature sequences characteristic of Type A, B, and C nonspecific bacterial acid phosphatases.
- Smiley-Moreno, Elizabeth,Smith, Douglas,Yu, Jieh-Juen,Cao, Phuong,Arulanandam, Bernard P.,Chambers, James P.
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- Synthesis-temperature-regulated multi-enzyme-mimicking activities of ceria nanozymes
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Ceria (CeO2) nanozymes have drawn much attention in recent years due to their unique physiochemical properties and excellent biocompatibility. It is therefore very important to establish a simple and robust guideline to regulate CeO2with desired multi-enzyme-mimicking activities that are ideal for practical bioapplications. In this work, the multi-enzyme-mimicking activities of CeO2were regulated in a facile manner by a wet-chemical method with different synthesis temperatures. Interestingly, a distinct response in multi-enzyme-mimicking activities of CeO2was observed towards different synthesis temperatures. And the regulation was ascribed to the comprehensive effect of the oxygen species, size, and self-restoring abilities of CeO2. This study demonstrates that high-performance CeO2can be rationally designed by a specific synthesis temperature, and the guidelines from radar chart analysis established here can advance the biomedical applications of ceria-based nanozymes.
- An, Xueying,Li, Sirong,Li, Tong,Lin, Anqi,Liu, Quanyi,Liu, Xiaoli,Wang, Quan,Wei, Hui,Wu, Jiangjiexing,Yang, Ming,Zhang, Yihong,Zhou, Zijun
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supporting information
p. 7238 - 7245
(2021/09/22)
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- A carbon dot-based Co-nanozyme with alkaline phosphatase-mechanism and application
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Elevated levels of alkaline phosphatase (ALP) are associated with bone metastasis, liver cancer, prostate cancer, breast cancer, and many other diseases or stem cell marker. It is therefore of great significance to quantitatively detect the ALP levels by
- Dukenbayev, Kanat,Fan, Haiyan,Khamijan, Medina,Ma, Cuiping,Sun, Qinglei,Tassanbiyeva, Aigerim,Turdaliyev, Akhrorbek,Xie, Yingqiu,Ysmaiyl, Alibek
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p. 33253 - 33259
(2021/12/07)
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- Microwave-assisted synthesis of para-nitrophenol using calcium nitrate
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Conventional process of nitrating phenolic compounds involves the use of excess corrosive reagents that impose environmental threats. Rapid and environmentally friendly microwave-assisted nitration of phenol has been employed to limit the use of corrosive
- Buan, Ivy Joyce Arenas,Duldulao, Dyanne Jane Cid
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p. 243 - 246
(2021/03/29)
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- Synthetic method of p-hydroxybenzonitrile
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The invention discloses a synthesis method of p-hydroxybenzonitrile, which comprises the following steps: carrying out diazotization reaction on p-hydroxyaniline to form a diazo compound, and reactingthe diazo compound with cuprous chloride and sodium cyanide to obtain the p-hydroxybenzonitrile. The p-hydroxyaniline is obtained by hydrogen reduction of p-nitrosophenol, and the p-nitrosophenol isobtained by nitrosation of phenol. The reaction temperature of each step is low, the reaction conditions are mild, and the reaction power consumption is greatly reduced. The reaction can be carried out by adopting a conventional reaction kettle, the equipment requirement is low, and the investment is small. According to the method, a dehydrating agent and filler are not used, only a small amount of catalyst is used, meanwhile, the catalyst can be recycled, the solid waste amount is small, only a small amount of solid catalyst is generated, and no difficult-to-treat wastewater is generated.
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Paragraph 0032-0034
(2021/01/30)
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- Synthetic method of antioxidant
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The invention discloses a synthesis method of an antioxidant, which comprises the following steps: reacting cyanuric chloride with an intermediate 8 and an intermediate 11 in sequence through temperature control to prepare an intermediate 12, hydrolyzing the intermediate 12, grafting a product on nano silicon dioxide to prepare the antioxidant; wherein the antioxidant is grafted with the nano silicon dioxide, so that the antioxidant can be fully dispersed when being mixed with a polymer, does not migrate along with the increase of service time, contains hindered phenol and phosphite structures, can provide hydrogen atoms to prevent the formation of chain free radicals, and reacts with the chain free radicals to achieve the purpose of inhibiting oxidation. Meanwhile, unstable hydrogen peroxide can be decomposed into stable compounds, so that formation of new free radicals is prevented, and the purpose of terminating a chain reaction is achieved.
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Paragraph 0020; 0032; 0037; 0039; 0044; 0046; 0051; ...
(2021/06/23)
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- Radical-anion coupling through reagent design: hydroxylation of aryl halides
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The design and development of an oxime-based hydroxylation reagent, which can chemoselectively convert aryl halides (X = F, Cl, Br, I) into phenols under operationally simple, transition-metal-free conditions is described. Key to the success of this approach was the identification of a reducing oxime anion which can interact and couple with open-shell aryl radicals. Experimental and computational studies support the proposed radical-nucleophilic substitution chain mechanism.
- Chechik, Victor,Greener, Andrew J.,James, Michael J.,Oca?a, Ivan,Owens-Ward, Will,Smith, George,Ubysz, Patrycja,Whitwood, Adrian C.
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p. 14641 - 14646
(2021/11/17)
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- ENGINEERED GYRI-LIKE MUTEIN APTAMERS, AND RELATED METHODS
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The present invention relates to the field of protein engineering, molecular imaging, and molecular diagnostics. More particularly, provided herein are novel synthetic aptamers produced using the GyrI-like family of proteins as a scaffold. Methods of obta
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Paragraph 34; 187
(2021/05/21)
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- Electronic-State Manipulation of Surface Titanium Activates Dephosphorylation Over TiO2 Near Room Temperature
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Dephosphorylation that removes a phosphate group from substrates is an important reaction for living organisms and environmental protection. Although CeO2 has been shown to catalyze this reaction, cerium is low in natural abundance and has a na
- Chen, Jian Lin,Chen, Yu-Cheng,Peng, Yung-Kang,Wang, Quan,Xiao, Yao,Yi, Xianfeng,Zheng, Anmin
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supporting information
p. 16149 - 16155
(2021/06/17)
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- Tantalum(v) peroxido complexes as phosphatase inhibitors: a comparative studyvis-a-visperoxidovanadates
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The present work illustrates the synthesis and comprehensive characterization of novel peroxidotantalum(v) complexes anchored to water soluble polymer (WSP) matricesviz., [Ta2(O2)6(carboxylate)2]-PA [PA = poly(s
- Ahmed, Kabirun,Gour, Nand Kishore,Islam, Nashreen S.,Saikia, Gangutri,Talukdar, Hiya
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p. 12848 - 12862
(2021/08/03)
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- Significant effects of the anion on the catalytic behaviour of sulfonic acid-functionalized ionic liquids in transesterification reactions – A combined electrochemical/catalytic study
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This work studies the strong influence of the counterion on the performance of ionic liquids (ILs) with sulfonic acid-functionalized butyl-imidazolic bases as homogeneous acid catalysts. Through a voltammetric analysis, it was shown that the availability
- Adam, Claudia G.,Fernández, José L.,Martini, María B.
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- Enzyme aggregation and fragmentation induced by catalysis relevant species
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It is usually assumed that enzymes retain their native structure during catalysis. However, the aggregation and fragmentation of proteins can be difficult to detect and sometimes conclusions are drawn based on the assumption that the protein is in its native form. We have examined three model enzymes, alkaline phosphatase (AkP), hexokinase (HK) and glucose oxidase (GOx). We find that these enzymes aggregate or fragment after addition of chemical species directly related to their catalysis. We used several independent techniques to study this behavior. Specifically, we found that glucose oxidase and hexokinase fragment in the presence ofd-glucose but notl-glucose, while hexokinase aggregates in the presence of Mg2+ion and either ATP or ADP at low pH. Alkaline phosphatase aggregates in the presence of Zn2+ion and inorganic phosphate. The aggregation of hexokinase and alkaline phosphatase does not appear to attenuate their catalytic activity. Our study indicates that specific multimeric structures of native enzymes may not be retained during catalysis and suggests pathways for different enzymes to associate or separate over the course of substrate turnover.
- Adair, James,Bhide, Ashlesha,Gentile, Kayla,Ghosh, Subhadip,Kauffman, Joshua,Lee, Tae-Hee,Maiti, Subhabrata,Sen, Ayusman
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p. 20709 - 20717
(2021/10/02)
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- α-Glucosidase inhibitory and anti-inflammatory activities of dammarane triterpenoids from the leaves of Cyclocarya paliurus
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Diabetes mellitus is caused by chronic inflammation and affects millions of people worldwide. Cyclocarya paliurus leaves have been widely used in traditional folk tea as a remedy for diabetes, but the antidiabetic constituents remain to be further studied. The α-glucosidase inhibitory and anti-inflammatory activities were examined to evaluate their effects on diabetes mellitus, and bioassay-guided separation of C. paliurus leaves led to the identification of twenty dammarane saponins, including eleven new dammarane saponins (1–11). The structures of the isolates were elucidated by spectroscopic methods. Bioactivity assay results showed that compounds 1 and 2 strongly inhibited α-glucosidase activity, with IC50 values ranging from 257.74 μM, 282.23 μM, and strongly inhibited the release of NO, with IC50 values of 9.10 μM, 9.02 μM. Moreover, compound 2 significantly downregulated the mRNA expression of iNOS, COX-2, IL-1β, NF-κB, IL-6 and TNF-α in LPS-mediated RAW 264.7 cells and markedly suppressed the protein expression of iNOS, NF-κB/p65, and COX-2. Dammarane glucoside 2 exhibited the strongest α-glucosidase inhibitory and anti-inflammatory activities. In addition, the structure–activity relationships (SARs) of the dammarane saponins were investigated. In summary, C. paliurus leaves showed marked α-glucosidase inhibitory and anti-inflammatory activities, and dammarane saponins are responsible for regulating α-glucosidase, inflammatory mediators, and mRNA and the protein expression of proinflammatory cytokines, which could be meaningful for discovering new antidiabetic agents.
- Deng, Shengping,Hao, Lili,Huang, Xishan,Huang, Yan,Li, Chenguo,Li, Jun,Liang, Cheng-qin,Liu, Wei,Su, Shanshan,Xu, Xia,Yang, Ruiyun,Zhang, Gaorong,Zhou, Dexiong
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supporting information
(2021/07/22)
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- A mild desilylation of phenolic tert-butyldimethylsilyl ethers using in situ generated tetraethylammonium superoxide
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Desilylation of phenolic tert-butyldimethylsilyl ethers has been achieved under the mild reaction conditions of in situ generated tetraethylammonium superoxide, at room temperature. (Figure presented.).
- Pandey, Surabhi,Shukla, Ajay K.,Raghuvanshi, Raghvendra S.
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p. 809 - 811
(2021/07/16)
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- The polyhedral nature of selenium-catalysed reactions: Se(iv) species instead of Se(vi) species make the difference in the on water selenium-mediated oxidation of arylamines
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Selenium-catalysed oxidations are highly sought after in organic synthesis and biology. Herein, we report our studies on the on water selenium mediated oxidation of anilines. In the presence of diphenyl diselenide or benzeneseleninic acid, anilines react with hydrogen peroxide, providing direct and selective access to nitroarenes. On the other hand, the use of selenium dioxide or sodium selenite leads to azoxyarenes. Careful mechanistic analysis and 77Se NMR studies revealed that only Se(iv) species, such as benzeneperoxyseleninic acid, are the active oxidants involved in the catalytic cycle operating in water and leading to nitroarenes. While other selenium-catalysed oxidations occurring in organic solvents have been recently demonstrated to proceed through Se(vi) key intermediates, the on water oxidation of anilines to nitroarenes does not. These findings shed new light on the multifaceted nature of organoselenium-catalysed transformations and open new directions to exploit selenium-based catalysis.
- Capperucci, Antonella,Dalia, Camilla,Tanini, Damiano
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supporting information
p. 5680 - 5686
(2021/08/16)
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- Scalable and hierarchically designed MOF fabrics by netting MOFs into nanofiber networks for high-performance solar-driven water purification
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Integrating metal-organic frameworks (MOFs) into flexible polymeric matrices can improve their practical processability and expand industrial applications greatly. However, current methods suffer from the serious aggregation of MOFs, low MOF loading, sacrifice of inherent pores in MOFs, and limited tunability of both MOFs and matrices. Herein, a novel net-fishing inspired strategy is developed for scalable and rapid production of high-performance MOF fabrics with tailored hierarchical architectures. It simultaneously realizes the good dispersion of individual MOF particles embedded into fishnet-like pores and achieves a maximum MOF loading of 85.7 wt%, while maintaining the inherent pore structures of the MOFs and enabling the convenient regulation of the functionality of the porous nanofibrous supports. Furthermore, a MOF fabric with UiO-66-NH2particles and carbon nanotubes (CNTs) confined inside functionalized polyacrylonitrile (PAN) nanofiber scaffolds is presented for solar-driven production of potable water from chemical warfare agent (CWA) simulant sewage. As a result, a record-breaking half-life of dimethyl-4-nitrophenyl phosphate (DMNP) and a promising water generation rate (2.97 L m?2d?1) are achieved. Owing to the versatility, our strategy provides a pioneering and fascinating platform for the future design of MOF fabrics with wide practical applications.
- Li, Ailin,Liu, Ye,Qin, Xiaohong,Wang, Liming,Xiong, Jian,Yu, Jianyong
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supporting information
p. 21005 - 21012
(2021/10/05)
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- Selective hydroxylation of aryl iodides to produce phenols under mild conditions using a supported copper catalyst
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Owing to the high activity and low-cost, copper-based catalysts are promising candidates for transforming aromatic halides to yield phenols. In this work, we report the selective hydroxylation of aromatic iodides to produce phenols using an atomically dispersed copper catalyst (Cu-ZnO-ZrO2) under mild reaction conditions. The reactions were conducted without the use of additional organic ligands, and the protection of an inert atmosphere environment is not required. The catalyst can be easily prepared, scalable, and is very efficient for a wide range of substrates. The catalytic reactions can be carried out with only 1.24 mol% Cu loading, which shows great potential in mass production.
- Auni, Anika,Ding, Guodong,Hao, Leiduan,Li, Tao,Li, Xiaoyu,Xu, Haiping,Zhang, Qiang
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p. 25348 - 25353
(2021/08/03)
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- Two key amino acids variant of α-l-arabinofuranosidase from bacillus subtilis str. 168 with altered activity for selective conversion ginsenoside rc to rd
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α-L-arabinofuranosidase is a subfamily of glycosidases involved in the hydrolysis of L-arabinofuranosidic bonds, especially in those of the terminal non-reducing arabinofuranosyl residues of glycosides, from which efficient glycoside hydrolases can be screened for the transformation of ginsenosides. In this study, the ginsenoside Rc-hydrolyzing α-L-arabinofuranosidase gene, BsAbfA, was cloned from Bacilus subtilis, and its codons were optimized for efficient expression in E. coli BL21 (DE3). The recombinant protein BsAbfA fused with an N-terminal His-tag was overexpressed and purified, and then subjected to enzymatic characterization. Site-directed mutagenesis of BsAbfA was performed to verify the catalytic site, and the molecular mechanism of BsAbfA catalyzing ginsenoside Rc was analyzed by molecular docking, using the homology model of sequence alignment with other β-glycosidases. The results show that the purified BsAbfA had a specific activity of 32.6 U/mg. Under optimal conditions (pH 5, 40?C), the kinetic parameters Km of BsAbfA for pNP-α-Araf and gin-senoside Rc were 0.6 mM and 0.4 mM, while the Kcat /Km were 181.5 s?1 mM?1 and 197.8 s?1 mM?1, respectively. More than 90% of ginsenoside Rc could be transformed by 12 U/mL purified BsAbfA at 40?C and pH 5 in 24 h. The results of molecular docking and site-directed mutagenesis suggested that the E173 and E292 variants for BsAbfA are important in recognizing ginsenoside Rc effectively, and to make it enter the active pocket to hydrolyze the outer arabinofuranosyl moieties at C20 position. These remarkable properties and the catalytic mechanism of BsAbfA provide a good alternative for the effective biotransformation of the major ginsenoside Rc into Rd.
- Guo, Zi Yu,Luo, Zhi Yong,Tan, Shi Quan,Tian, Liang Yu,Weng, Pei,Zhang, Bian Ling,Zhang, Ru
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- Highly recyclable Ti0.97Ni0.03O1.97catalyst coated on cordierite monolith for efficient transformation of arylboronic acids to phenols and reduction of 4-nitrophenol
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A stable Ni2+substituted TiO2catalyst (Ti0.97Ni0.03O1.97) has been synthesized by a solution combustion method with an average crystallite size of 7.5 nm. Ti1?xNixO2?x(x= 0.01-0.06) crystallizes in the TiO2anatase structure with Ni2+substituted in Ti4+ion sites and Ni taking a nearly square planar geometry. This catalyst is found to be highly active in the transformation of diverse arylboronic acids to the corresponding phenols. The catalyst coated cordierite monolith can even be recycled for up to 20 cycles with a cumulative TOF of 1.8 × 105h?1. In scale-up reactions, various phenols are synthesized by employing a single cordierite monolith. It also shows high performance in the reduction of 4-nitrophenol.
- Hegde, M. S.,Prasanna,Usha, K. M.
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supporting information
p. 14223 - 14234
(2021/10/25)
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- A Dual-Function Highly Crystalline Covalent Organic Framework for HCl Sensing and Visible-Light Heterogeneous Photocatalysis
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Covalent organic frameworks (COFs) offer great potential for various advanced applications such as photocatalysis, sensing, and so on because of their fully conjugated, porous, and chemically stable unique structural architecture. In this work, we have designed and developed a truxene-based ultrastable COF (Tx-COF-2) by Schiff-base condensation between 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 5,5,10,10,15,15-hexamethyl-10,15-dihydro-5H-diindeno(1,2-a:1′,2′-c)fluorene-2,7,12-tricarbaldehyde (Tx-CHO) for the first time. The resulting COF possesses excellent crystallinity, permanent porosity, and high Brunauer-Emmett-Teller (BET) surface areas (up to 1137 m2 g-1). The COF was found to be a heterogeneous, recyclable photocatalyst for efficient conversion of arylboronic acids to phenols under visible-light irradiation, an environmentally friendly alternative approach to conventional metal-based photocatalysis. Besides, Tx-COF-2 provides an immediate naked-eye color change (1 s) and fluorescence "turn-on"phenomena upon exposure to HCl. The response is highly sensitive, with an ultralow detection limit of up to 4.5 nmol L-1.
- Addicoat, Matthew A.,Nailwal, Yogendra,Pal, Santanu Kumar,Wonanke, A. D. Dinga
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p. 6595 - 6604
(2021/07/20)
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- Double Insurance of Continuous Band Structure and N-C Layer Induced Prolonging of Carrier Lifetime to Enhance the Long-Wavelength Visible-Light Catalytic Activity of N-Doped In2O3
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Nonmetallic doped metal oxides can be broad in their visible-light-response range. However, the half-filled or isolated impurity state can also be the new recombination center for photogenerated electrons/holes, which seriously influence the photocatalytic activity of the catalyst in the visible-light region. Therefore, how to prolong the photogenerated carrier life of nonmetallic doping metal oxides is the difficult and challenging topic in the field of photocatalysis. In this work, the hexagonal nanosheets assembled by N-doped C (N-C)-coated N-doped In2O3 (N-In2O3) nanoparticles (N-C/N-In2O3 HS) was obtained by simply pyrolyzing the In(2,5-PDC) hexagonal sheets. The N-C/N-In2O3 HS catalyst exhibit good photocatalytic activity and cycle stability in the long-wavelength region of visible light (λ = 520 and 595 nm). The effective utilization of long-wavelength visible light for N-C/N-In2O3 HS was mainly attributed to the acceptor-donor-acceptor compensation mechanism between the oxygen vacancy (VO) and substitutional N-doping (Ns) sites, which made the N-C/N-In2O3 HS possess a continuous band structure, without the half-filled or isolated impurity state in the band gap, and extended its light absorption edge to 733 nm. The compensation mechanism of nitrogen doping on In2O3 can promote the photocatalytic activity under longer-wavelength yellow light (595 nm) irradiation. The N-C layer coated on the N-In2O3 nanoparticles acted as a good acceptor of photogenerated electrons, facilitating the effective spatial separation of photogenerated carriers and extend photogenerated carrier lifetimes. The comparative photocatalytic experiments (N-In2O3 HS and N-C/N-In2O3 HS) show that the presence of N-doped C layer can enhance the photocatalytic efficiency by nearly 10-fold. This double-doping and carbon-coating strategy provided a novel research idea to solve the problem that nonmetal atoms doped metal oxides led to the secondary combination of photogenerated electrons/holes.
- Sun, Liming,He, Xiaoxiao,Zeng, Suyuan,Yuan, Yusheng,Li, Rong,Zhan, Wenwen,Chen, Jinquan,Wang, Xiaojun,Han, Xiguang
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supporting information
p. 1160 - 1171
(2021/01/18)
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- Application of Electron-Rich Covalent Organic Frameworks COF-JLU25 for Photocatalytic Aerobic Oxidative Hydroxylation of Arylboronic Acids to Phenols
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Visible-light-driven organic reactions are environmentally friendly green chemical transformations among which photosynthetic oxidative hydroxylation of arylboronic acids to phenols has attracted increasing research interest during the very recent years. Given the efficiency and reusability of heterogeneous catalysts, COF-JLU25, an electron-rich COF-based photocatalyst constructed by integrating electron-donating blocks 1,3,6,8-tetrakis(4-aminophenyl)pyrene (PyTA) and 4-[4-(4-formylmethyl)-2,5-dimethoxyphenyl] benzaldehyde (TpDA), was selected as a photocatalyst for the oxidative hydroxylation of arylboronic acids. In our studies, COF-JLU25 demonstrated excellent photocatalytic activity with high efficiency, robust reusability, and low catalyst loading, showcasing an application potential of previously underexplored COF-based photocatalyst composed solely of electron-rich units.
- Xiao, Guangjun,Li, Wenqian,Chen, Tao,Hu, Wei-Bo,Yang, Hui,Liu, Yahu A.,Wen, Ke
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supporting information
p. 3986 - 3991
(2021/03/29)
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- Transforming a Fluorochrome to an Efficient Photocatalyst for Oxidative Hydroxylation: A Supramolecular Dimerization Strategy Based on Host-Enhanced Charge Transfer
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The development of non-covalent synthetic strategy to fabricate efficient photocatalysts is of great importance in theranostic and organic materials. Herein, a fluorochrome N,N′-dimethyl 2,5-bis(4-pyridinium)thiazolo[5,4-d]thiazolediiodide (MPT) was transformed into an efficient photocatalyst through supramolecular dimerization in the cavity of cucurbit[8]uril (CB[8]). The host-enhanced charge transfer interaction within the supramolecular dimer 2MPT-CB[8] dramatically promoted intersystem crossing to produce triplet. In addition, the staggered conformation of 2MPT-CB[8] facilitated the energy transfer and electron transfer of the triplet. As a result, 2MPT-CB[8] could serve as a high-efficiency photocatalyst for the oxidative hydroxylation of arylboronic acids. This supramolecular dimerization strategy enriches the supramolecular engineering of functional π-systems. It is anticipated that this strategy can be extended to fabricate various π-systems with tailor-made functions.
- Tang, Bohan,Xu, Weiquan,Xu, Jiang-Fei,Zhang, Xi
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supporting information
p. 9384 - 9388
(2021/03/22)
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- An efficient Ti0.95Cu0.05O1.95 catalyst for ipso – hydroxylation of arylboronic acid and reduction of 4-nitrophenol
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A stable, active and selective Ti0.95Cu0.05O1.95 catalyst, crystallized in anatase TiO2 structure with 5% Cu2+ ions substituted for Ti4+ ions with 5% oxide ion vacancy has been synthesized by solution combustion method. The catalyst was coated over a cordierite monolith (Mg2Al4Si5O18) by solution combustion method. By the first principle density functional theory (DFT) calculations, 48 atoms bulk structure has been optimized and density of states (DOS) has been calculated. Ti – O bond distribution in Ti0.95Cu0.05O1.95 has been compared with pure TiO2. Bond distribution analysis has shown longer Cu – O and Ti – O bonds compared to those in CuO and TiO2 creating Cu2+ and oxide ion vacancy as electrophilic and nucleophilic active sites, respectively. This catalyst was found to be very active for ipso – hydroxylation of arylboronic acid and 4-nitrophenol reduction reactions at room temperature. Catalyst coated cordierite monolith was used in the recycling process of the reaction for 20 cycles and cumulative turnover frequency was found to be 184,840 h?1. Ti0.95Cu0.05O1.95 catalyst coated on cordierite monolith enhanced the rate of the reaction compared to powder catalyst and made the handling and recycling of the catalyst very easy. Graphic abstract: [Figure not available: see fulltext.]
- Bhat, Shrikanth K,Dasappa, Jagadeesh Prasad,Hegde, M. S.,Prasanna
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- Substituent and Surfactant Effects on the Photochemical Reaction of Some Aryl Benzoates in Micellar Green Environment?
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In this study, we carried out preparative and mechanistic studies on the photochemical reaction of a series of p-substituted phenyl benzoates in confined and sustainable micellar environment. The aim of this work is mainly focused to show whether the nature of the surfactant (ionic or nonionic) leads to noticeable selectivity in the photoproduct formation and whether the electronic effects of the substituents affect the chemical yields and the rate of formation of the 5-substituted-2-hydroxybenzophenone derivatives. Application of the Hammett linear free energy relationship (LFER) on the rate of formation of benzophenone derivatives, on the lower energy band of the UV-visible absorption spectra of the aryl benzoates and 5-substituted-2-hydroxybenzophenone derivatives allows a satisfactory quantification of the substituent effects. Furthermore, UV-visible and 2D-NMR (NOESY) spectroscopies have been employed to measure the binding constant Kb and the location of the aryl benzoates within the hydrophobic core of the micelle. Finally, TD-DFT calculations have been carried out to estimate the energies of the absorption bands of p-substituted phenyl benzoates and 5-substituted-2-hydroxybenzophenone derivatives providing good linear correlation with those values measured experimentally.
- Siano, Gastón,Crespi, Stefano,Bonesi, Sergio M.
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p. 1298 - 1309
(2021/05/07)
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- Isomer of linker for NU-1000 yields a newshe-type, catalytic, and hierarchically porous, Zr-based metal-organic framework
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The well-known MOF (metal-organic framework) linker tetrakis(p-benzoate)pyrene (TBAPy4?) lacks steric hindrance between its benzoates. Changing the 1,3,6,8-siting of benzoates in TBAPy4?to 4,5,9,10-siting introduces substantial steric hindrance and, in turn, enables the synthesis of a new hierarchically porous,she-type MOF Zr6(μ3-O)4(μ3-OH)4(C6H5COO)3(COO)3(TBAPy-2)3/2(NU-601), where TBAPy-24?is the 4,5,9,10 isomer of TBAPy4?.NU-601shows high catalytic activity for degradative hydrolysis of a simulant for G-type fluoro-phosphorus nerve agents.
- Lu, Zhiyong,Wang, Rui,Liao, Yijun,Farha, Omar K.,Bi, Wentuan,Sheridan, Thomas R.,Zhang, Kun,Duan, Jiaxin,Liu, Jian,Hupp, Joseph T.
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p. 3571 - 3574
(2021/04/14)
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- Kinetic Resolution of Nearly Symmetric 3-Cyclohexene-1-carboxylate Esters Using a Bacterial Carboxylesterase Identified by Genome Mining
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A new bacterial carboxylesterase (CarEst3) was identified by genome mining and found to efficiently hydrolyze racemic methyl 3-cyclohexene-1-carboxylate (rac-CHCM) with a nearly symmetric structure for the synthesis of (S)-CHCM. CarEst3 displayed a high substrate tolerance and a stable catalytic performance. The enantioselective hydrolysis of 4.0 M (560 g·L-1) rac-CHCM was accomplished, yielding (S)-CHCM with a >99% ee, a substrate to catalyst ratio of 1400 g·g-1, and a space-time yield of 538 g·L-1·d-1.
- Dou, Zhe,Chen, Xuanzao,Niwayama, Satomi,Xu, Guochao,Ni, Ye
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supporting information
p. 3043 - 3047
(2021/05/05)
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- Reactions of 4-Nitrophenyl 5-substituted Furan-2-carboxylates with R2NH/R2NH2+ in 20 mol% DMSO(aq): Effect of Aryl Group on the Acyl-Transfer Reaction
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Reactions of 4-nitrophenyl 2-furoates (1a–e) with R2NH/R2NH2+ in 20 mol% DMSO(aq) have been studied. The reactions produced aminolysis products and exhibited second-order kinetics. The Br?nsted plots were linear with βnuc values of 0.75–0.89, which remained nearly the same for all 5-furyl substituents. The rate data showed excellent correlations on the Yukawa-Tsuno plots with ρ(x)?=?0.72–1.1, and r?=?0.55–0.95, respectively. The ρ value increased and r value decreased with a stronger nucleophile, indicating an increase in the electron density at the C-O bond and a decrease in the resonance contribution. The results have been interpreted with the addition–elimination mechanism in which the second step is the rds. By comparing with the data for ArC(O)OC6H4-4-NO2 (Ar?=?Ph, thienyl), the effect of the aryl group on the acyl transfer reaction was assessed.
- Pyun, Sang Yong,Paik, Kyu Cheol,Han, Man So,Cho, Bong Rae
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supporting information
p. 994 - 1000
(2021/05/11)
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- Nucleofugality hierarchy, in the aminolysis reaction of 4-cyanophenyl 4-nitrophenyl carbonate and thionocarbonate. Experimental and theoretical study
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Nucleophilic substitution reactions of the title compounds have been investigated with a series of secondary alicyclic amines in several solvents. The solvent, amine, and electrophilic group effects on kinetics, mechanism and nucleofugality hierarchy are discussed from experimental and theoretical studies. These studies show the mechanistic dependence on the solvent polarity; the theoretical results indicate that the relative polarization of the reactive centres (CO and CS) and the stabilization of the nucleofuges are the main factors in the control of the product distribution.
- Aliaga, Margarita E.,Cornejo, Patricio,Montecinos, Rodrigo,Pavez, Paulina,Santos, José G.
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p. 11495 - 11505
(2021/07/12)
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- Efficient hydrolytic cleavage of phosphodiester with a lanthanide-based metal-organic framework
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Hydrolysis of phosphate diesters has attracted substantial research efforts, not only in bio-organic chemistry, but also in inorganic chemistry. Herein, a lanthanide-based metal-organic framework was synthesized by incorporating a tetraphenylethylene moiety as the four-point connected node, Ce-TCPE (noted as 1). The structural analyses indicate that 1 exhibits 3D framework connected by the sharing carboxylate groups with two kinds of 1D rhombic channels when viewed along the c direction. Hydrolytic cleavage catalysis have been performed and showed that 1 could act as efficient heterogeneous catalyst for the hydrolytic cleavage of the phosphodiester BNPP (bis(p-nitrophenyl)phosphate) with the high activity and hydrolytic stability in a pseudo-first-order rate. DFT studies has also gain an insight analysis to elucidate the cleavage process.
- Dong, Yunhui,Dou, Yong,Qin, Lan,Yang, Lu,Zhang, Daopeng,Zhou, Zhen
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