- High tenacity regenerated chitosan fibers prepared by using the binary ionic liquid solvent (Gly·HCl)-[Bmim]Cl
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A binary ionic liquid system was confirmed to be a promising solvent to dissolve chitosan, and the regenerated chitosan fibers were prepared by wet and dry-wet spinning technique respectively. The SEM results show that the chitosan fibers prepared by wet spinning technique present striated surface and round cross section, and the chitosan fibers prepared by dry-wet spinning technique present smooth surface and irregular cross section. The mechanical testing results show that the regenerated chitosan fibers present relatively high tenacity, especially, these prepared by dry-wet spinning process present excellent strength and initial modulus, i.e. 2.1 cN/dtex and 83.5 cN/dtex, which is stronger than that of most reported chitosan fibers. The FT-IR results show that the dissolution of chitosan in the binary ionic liquid system is due to the protonation of NH2 groups in the chitosan chains. Furthermore, a possible reaction during the dissolution and regeneration process is proposed.
- Ma, Bomou,Qin, Aiwen,Li, Xiang,He, Chunju
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- Vibrational and NMR spectroscopic study of aged flurazepam mono- and dihydrochloride salts for content identity
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Archival samples of flurazepam monohydrochloride and 'hydrochloride' (i.e., the dihydrochloride) were examined by Fourier transform infrared and Raman spectroscopy to determine evidence of degradation during storage for 13-15 years. No degradation of the three different batches of monohydrochloride salts was detected, but various degrees of degradation of the eight specimens of flurazepam hydrochloride diprotonated salts were indicated by enhanced intensities (IR 1635, 1509, 1226; Raman 1636, 1408, 1149 cm-1) and new features (IR 1742, 943, 755; Raman 1554, 837, 742 cm- 1). All of these features, except the 1742 cm-1 IR band, were attributed to the presence of the hydrolysis product 5-chloro-2-[[2- (diethylamino)ethyl]amino]-2'-fluorobenzophenone hydrochloride whereas the 1742 cm-1 band was attributed to glycine hydrochloride, the other hydrolytic moiety. The flurazepam hydrochloride samples were also examined in deuterated dimethyl sulfoxide solution by proton nuclear magnetic resonance (1H-NMR) spectroscopy to verify the presence of the degradation products and to estimate the levels of degradation (~3-36%) of the drug. IR and Raman spectra of the 'benzophenone' hydrochloride in the 'fingerprint' region are compared with two samples of flurazepam dihydrochloride (slightly and highly degraded) and their features discussed. Vibrational assignments are made and discussed for the observed IR and Raman wavenumbers for the 'benzophenone' hydrochloride.
- Neville,Beckstead,Black,Dawson,Shurvell
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- Preparation of high strength chitosan fibers by using ionic liquid as spinning solution
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The morphology and mechanical properties of chitosan fibers obtained by wet-spinning using chitosan-[Gly]Cl (glycine chloride) ionic liquid as spinning dope solution are reported for the first time. The objectives were to understand both how the microstructure of the fibers could be modified and how the mechanical properties were improved by means of using [Gly]Cl ionic liquid as the spinning solution. In the new system, the main component chitosan (the degree of deacetylation was 86%, the molecular weight was about 1.5 × 106) was dissolved in an aqueous [Gly]Cl ionic liquid solution; the fibers were then spun using a sodium sulfate (Na2SO 4)/ethanol (C2H5OH) aqueous solution as the coagulant, and then directly dried under freeze-drying. The fibers spun from the above mentioned system have the chitosan I crystal form, and the breaking tenacity (3.77 cN dtex-1) is 4 times more than that (0.86 cN dtex-1) from an acetic acid system. The orientation and crystallinity of fibers spun in [Gly]Cl solution was enhanced with an increase of spin stretch ratio, and thereby the mechanical properties of the fibers were improved. Moreover, the fibers had a smooth surface as well as a round and compact structure. More to the point, the used [Gly]Cl could be recovered by simple post processing and the chitosan fibers spun in the recycled [Gly]Cl solution also had a strong breaking tenacity. Therefore, this study verified that [Gly]Cl is a new spinning dope solution for preparing chitosan fibers with strong mechanical properties. The Royal Society of Chemistry 2012.
- Li, Lu,Yuan, Bing,Liu, Shiwei,Yu, Shitao,Xie, Congxia,Liu, Fusheng,Guo, Xianying,Pei, Lijun,Zhang, Baoquan
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- New binary ionic liquid system for the preparation of chitosan/cellulose composite fibers
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A binary system consisting of acidic ionic liquid glycine hydrochloride (Gly·HCl) and neutral ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) is proposed to be cosolvent for chitosan and cellulose, the spinning solution of chitosan/cellulose can be prepared in one step. The regenerated chitosan/cellulose composite fiber with 9.4 wt.% chitosan was prepared through dry-wet spinning process. SEM shows that the chitosan is scattered on the surface and interior of the composite fiber. WAXD shows that the degree crystallization of the composite fibers is far less than that of raw materials. The result of elemental analysis (EA) indicates that there is little weight loss of chitosan during the spinning process. Moreover, the prepared composite fiber presents good thermal stability, i.e. its Tonset is 305.1 °C, and excellent mechanical property, i.e. its tensile strength is 4.63 cN/dtex. All the results show that Gly·HCl/[Bmim]Cl binary system is a promising solvent for the preparation of chitosan/cellulose composite fiber.
- Ma, Bomou,Zhang, Meng,He, Chunju,Sun, Junfen
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- Efficient novel eutectic-mixture-mediated synthesis of benzoxazole-linked pyrrolidin-2-one heterocycles
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In this study, new benzoxazole-linked pyrrolidinone heterocyclic compounds were synthesized by an eco-efficient strategy using substituted benzylamines and 2-aminophenol under ultrasonic irradiation in the presence of a newly designed metal-free deep eutectic solvent (DES). This DES was prepared by using a eutectic mixture of urea and a synthesized glycine-derived ionic liquid. X-ray diffraction and infrared spectroscopy were employed to investigate the structure of the ionic liquid and characterize the DES, respectively. This method exhibited key advantages of high productivity, a short reaction time, and simple processing. Moreover, this DES was easily separated from reaction mixtures and can be recycled for multiple reactions.
- Anouar, El Hassane,Geesi, Mohammed H.,Guionneau, Philippe,Kaiba, Abdellah,Ouerghi, Oussama,Riadi, Yassine
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- Synthesis of 2-Aminocarboxylic Acids on the Basis of Metalated Lithium Acylates
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2-Aminocarboxylic acids have been synthesized through the reaction of lithium acylate α-carbanions with alkyl nitrites to form α-hydroxyiminoacylates, followed by reduction of the latter with tin chloride. The reactions of lithium acylate α-carbanions, ge
- Zorin,Lenkova,Khachaturyan,Zorin
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p. 1590 - 1594
(2018/11/10)
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- LAT1 activity of carboxylic acid bioisosteres: Evaluation of hydroxamic acids as substrates
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Large neutral amino acid transporter 1 (LAT1) is a solute carrier protein located primarily in the blood–brain barrier (BBB) that offers the potential to deliver drugs to the brain. It is also up-regulated in cancer cells, as part of a tumor's increased metabolic demands. Previously, amino acid prodrugs have been shown to be transported by LAT1. Carboxylic acid bioisosteres may afford prodrugs with an altered physicochemical and pharmacokinetic profile than those derived from natural amino acids, allowing for higher brain or tumor levels of drug and/or lower toxicity. The effect of replacing phenylalanine's carboxylic acid with a tetrazole, acylsulfonamide and hydroxamic acid (HA) bioisostere was examined. Compounds were tested for their ability to be LAT1 substrates using both cis-inhibition and trans-stimulation cell assays. As HA-Phe demonstrated weak substrate activity, its structure–activity relationship (SAR) was further explored by synthesis and testing of HA derivatives of other LAT1 amino acid substrates (i.e., Tyr, Leu, Ile, and Met). The potential for a false positive in the trans-stimulation assay caused by parent amino acid was evaluated by conducting compound stability experiments for both HA-Leu and the corresponding methyl ester derivative. We concluded that HA's are transported by LAT1. In addition, our results lend support to a recent account that amino acid esters are LAT1 substrates, and that hydrogen bonding may be as important as charge for interaction with the transporter binding site.
- Zur, Arik A.,Chien, Huan-Chieh,Augustyn, Evan,Flint, Andrew,Heeren, Nathan,Finke, Karissa,Hernandez, Christopher,Hansen, Logan,Miller, Sydney,Lin, Lawrence,Giacomini, Kathleen M.,Colas, Claire,Schlessinger, Avner,Thomas, Allen A.
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supporting information
p. 5000 - 5006
(2016/10/05)
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- Cyclopeptides and polyketides from coral-associated fungus, Aspergillus versicolor LCJ-5-4
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Three new cyclopentapeptides, versicoloritides A-C (1-3), a new orcinol tetramer, tetraorcinol A (4), and two new lactones, versicolactones A and B (5 and 6) together with three known metabolites, diorcinol, glyantrypine, and cordyol C were isolated from the fermentation broth of the coral-associated fungus Aspergillus versicolor LCJ-5-4. Their structures were elucidated by spectroscopic and chemical methods. The new compounds 1-4 were evaluated for their radical-scavenging activity and antimicrobial activity against Staphylococcus aureus, Escherichia coli, Enterobacter aerogenes, Bacillus subtilis, Pseudomonas aeruginosa, and Candida albicans and cytotoxicity against P388 and Hela cell lines. Compound 4 showed weak radical-scavenging activity against the DPPH radical with an IC50 value of 67 μM.
- Zhuang, Yibin,Teng, Xiancun,Wang, Yi,Liu, Peipei,Wang, Hui,Li, Jing,Li, Guoqiang,Zhu, Weiming
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experimental part
p. 7085 - 7089
(2011/10/09)
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- RELAXIN-FUSION PROTEINS WITH EXTENDED IN VIVO HALF-LIVES
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Disclosed are human relaxin-Fc fusion proteins having an increased serum half-life, polynucleotides encoding the same, and intermediates formed during the fusion protein biosynthesis. The fusion proteins may include a linker portion or other sections as well. Suitable fusion proteins are also those predicted to have the same effect as human relaxin in vivo, based, for example, on structural modeling. The fusion protein is useful in the treatment of a number of diseases and conditions, including heart disease, vascular disease, wound healing, fibrosis, fibromyalgia, and promoting angiogenesis.
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- Hydration of amino acids from ultrasonic measurements
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In this paper the results of compressibility of aqueous solutions of amino acids in water and in aqueous HCl and NaOH solutions at 25 °C are presented. The effect of the charged protonated amino groups and deprotonated carboxylic groups on the hydration number was tested. The idea of additivity of the hydration number with the constituents of the solute molecule was successfully applied and discussed.
- Burakowski, Andrzej,Gliński, Jacek
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experimental part
p. 12157 - 12161
(2011/01/11)
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- Novel cyclopeptide and unique flavone from Desmos rostrata. Total synthesis of desmorostratone
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Two new compounds, a cyclic peptide desmocyclopeptide (1) and a special flavone desmorostratone (2) were isolated from the stem bark of Desmos rostrata, along with two known compounds, desmosdumotins B (3) and C (4). Their structures were established on the basis of the spectral data, including mass spectrometry and 2D NMR. The total synthesis of desmorostratone (2) was performed in order to confirm its structure as well as that of desmosdumotin C (4), which was a tautomeric mixture in the solution. Finally, cytotoxity of these compounds were evaluated. Desmosdumotin C (4) displayed a moderate inhibition activity against KB cell line with an IC50 of 19.2 μM, whereas the other products showed a weak inhibition against the same cell line target.
- Nguyen, Ngoc Tuan,Pham, Van Cuong,Litaudon, Marc,Guéritte, Fran?oise,Bodo, Bernard,Nguyen, Van Tuyen,Nguyen, Van Hung
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experimental part
p. 7171 - 7176
(2009/12/24)
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- Investigations on the physicochemical properties of the nonlinear optical crystal for blue green laser generation
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Bisglycinehydrogenchloride (BGHC) an intriguing material for frequency conversion has been grown by slow evaporation solution growth technique at room temperature. Their structural, optical and physicochemical properties were characterized by X-ray powder diffraction, FTIR, Raman and UV-vis spectra. The title crystal has found to crystallize into noncentrosymmetric orthorhombic P212121 space group. The material has a wide transparency in the entire visible region. It is found that the cutoff wavelength lies in the UV region. The mechanical response of the crystal has been studied using Vickers microhardness technique. The Kurtz powder second harmonic generation test shows that the compound is a prospective crystalline material for second order nonlinear optical application.
- Krishnakumar,Sivakumar,Nagalakshmi
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experimental part
p. 119 - 124
(2009/02/04)
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- Thermodynamics of protonation of amino acid carboxylate groups from 50 to 125°C
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Flow calorimetry has been used to study the interaction of glycine, DL-α-alanine, DL-2-aminobutyric acid, β-alanine, 4-aminobutyric acid, and 6-aminocaproic acid with protons in aqueous solutions from 323.15 K to 398.15 K and at 1.52 MPa. LogK, ΔH°, ΔS°, and ΔC°p for the protonation of the carboxylate groups of these amino acids have been obtained at each temperature studied. Equations are given expressing these values as functions of temperature. The protonation reactions are exothermic at lower temperatures and become endothermic as temperature increases. The logK, ΔH°, and ΔS° values are close together over the temperature range studied for the protonation of α-amino acids, i.e., glycine, DL-α-a/anine, and 2-aminobutyric acid. At each temperature, the magnitudes of these thermodynamic quantities increase as the number of methylene groups between the amino group and the carboxylate group increases. The ΔC°p value for the protonation of the carboxyl group is found to lie between those of an isocoulombic reaction and a charge reduction reaction. At 323.15 K, the protonation reactions of the carboxylate groups have larger ΔC°p values which approach those associated with charge reduction reactions. As the temperature increases, ΔC°p decreases and approaches those found for isocoulombic reactions. This result is explained by considering long-range and short-range solvent effects. The trend in ΔH° and ΔS° with temperature and with charge separation in the zwitterions is interpreted in terms of solvent-solute interactions and the electrostatic interaction of the two oppositely charged groups within the molecule.
- Wang, Peiming,Oscarson, John L.,Gillespie, Sue E.,Izatt, Reed M.,Cao, Hongjie
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p. 243 - 266
(2007/10/03)
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- Process for preparing glycine hydrochloride
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An improved process for preparing glycine hydrochloride in a high purity and high yield employing water as the solvent.
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- Studies Related to Thietan-2-ones. Part 2. Conversion of a Benzylpenicillin-derived Thietan-2-one into D- and L-2-Methylpenicillamines
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(3R)- and (3S)-hept-2-en-6-yl>-3,4,4-trimethylthietan-2-ones (8b) and (9b) were isomerised to (3R)- and (3S)-3-(2-benzyloxazol-5-ylcarbonyl)amino-3,4,4-trimethylthietan-2-ones (10) and (14) by m-chlorobenzoic acid in methanol.Attempts to cleave the amide linkage of compound (10), by the action of phosphorus(V) chloride-methanol, were unrewarding.In dichloromethane containing boron trifluoride, compound (8b) was converted into (3R)-3-(2-benzyl-5-oxo-2-oxazolin-4-ylidene)amino-3,4,4-trimethylthietan-2-one (16).Ozonolysis of the lastmentioned compound in dichloromethane at -78 deg C and addition of ethanol yielded (3R)-3-(formyl)amino-3,4,4-trimethylthietan-2-one (17) and N-(ethoxycarbonyl)phenylacetamide (22a).Removal of the formyl group from compound (17) was achieved by the action of phosphorus(V) trichloride oxide-methanol to give, following addition of toluene-p-sulphonic acid, (3R)-3-amino-3,4,4-trimethylthietan-2-one toluene-p-sulphonate (4c).In boiling water, the thietanone (4c) underwent hydrolysis to give (2S)-2-amino-2,3-dimethyl-3-mercaptobutanoic acid toluene-p-sulphonate (D-2-methylpenicillamine toluene-p-sulphonate) (27b).Using a similar reaction sequence, the thietanone (9b) was transformed into L-2-methylpenicillamine toluene-p-sulphonate (28b).D-Penicillamine toluene-p-sulphonate (27a) underwent thiazolidine formation with formaldehyde more rapidly than did compound (27b).
- Crilley, Martine M. L.,Stoodley, Richard J.
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p. 1127 - 1132
(2007/10/02)
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- A New α-Amino Acid Synthesis via an Acetimidate Rearrangement
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A new efficient synthesis of α-amino acids from allyl alcohol derivatives via an acetimidate rearrangement has been developed.
- Takano, Seiichi,Akiyama, Masashi,Ogasawara, Kunio
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p. 770 - 771
(2007/10/02)
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- Correlative Variations in Enzyme-Derived and Substrate-Derived Structures of Catalytic Transition States. Implications for the Catalytic Strategy of Acyl-Transfer Enzymes
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Acetylchymotrypsin, acetyl elastase and (carbobenzyloxy)glycyl elastase all undergo hydrolysis with the same overall solvent isotope effect, which arises from a single protonic site n/k1 = 2.45(1-n + n/2.45)>. chymotrypsin, however, shows a larger effect arising from at least two sites n/k1 = 3.34(1-n + n/1.85)2>.Formylchymotrypsin and acetylchymotrypsin undergo deacylation with α-deuterium and β-deuteium secondary isotope effects, respectively, that suggest fractional tetrahedral character at the transition state of about 0.44 (vs. 0.58 - 0.66 for similar nonenzymic reactions) when compared to equilibrium isotope effects for complete addition.The effect for acetyl elastase suggests much less tetrahedral character (0.27).Addition of an N-acyl function leads to a more inverse isotope effect, per deuterium, and thus to an apparent increase in tetrahedral character: to 0.84 for chymotrypsin; to 0.43 for (carbobenzyloxy)glycyl elastase.It is concluded that enzyme-substrate interactions at the transition state can alter both enzyme structure, as shown by the solvent isotope effects, and substrate structure as shown by the substrate isotope effects.Such alterations, in the combination of enzyme with natural substrate, probably adjust both structures for optimal catalytic interaction.
- Stein, Ross L.,Elrod, James P.,Schowen, Richard L.
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p. 2446 - 2452
(2007/10/02)
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- Aminosaeuren, I. Darstellung von Aminosaeuren aus Halogencarbonsaeure-alkylestern mit Alkalimetallcyanaten
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α- and ω-halo- as well as α,ω-dihalocarboxylic alkyl esters react with potassium cyanate in the presence of alcohol at 80 - 120 deg C in dipolar aprotic solvents to yield α- and ω-(alkoxycarbonylamino)- and α,ω-bis(alkoxycarbonylamino)carboxylic alkyl esters, respectively, in good yields.Hydrolytic cleavage of these mono- or diurethanes with an aqueous solution of hydrochloric acid/formic acid leads to the corresponding amino acid hydrochlorides in nearly quantitative yields.
- Effenberger, Franz,Drauz, Karlheinz,Foerster, Siegfried,Mueller, Wolfgang
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p. 173 - 189
(2007/10/02)
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