- Ozone and ozone/vacuum-UV degradation of diethyl dithiocarbamate collector: Kinetics, mineralization, byproducts and pathways
-
The diethyl dithiocarbamate (DDC) collector, a precursor of toxic N-nitrosamines, is detected in flotation wastewaters usually at the ppm level. In this study, the O3 and O3/Vacuum-UV (O3/VUV) processes were compared to investigate the efficient removal of DDC with a low risk of N-nitrosamine formation. The results showed that 99.55% of DDC was removed at 20 min by O3/VUV, and the degradation rate constant was 3.99 times higher than that using O3-alone. The C, S and N mineralization extents of DDC using O3/VUV reached 36.36%, 62.69% and 79.76% at 90 min, respectively. O3/VUV achieved a much higher mineralization extent of DDC than O3-alone. After 90 min of degradation, O3/VUV achieved lower residual concentrations of CS2 and H2S, and released lower amounts of gaseous sulfur byproducts compared to O3-alone. The solid phase extraction and gas chromatography-mass spectrometry (SPE/GC-MS) analysis indicated that the main byproducts in O3/VUV degradation of DDC were amide compounds without the detection of N-nitrosamines. The avoidance of N-nitrosamine formation might be attributed to exposure of UV irradiation and enhanced formation of OH radicals in the O3/VUV system. The degradation pathways of DDC were proposed. This work indicated that O3/VUV was an efficient alternative treatment technique for the removal of DDC flotation collector with low risk of N-nitrosamine formation.
- Fu, Pingfeng,Ma, Yanhong,Yang, Huifen,Li, Gen,Lin, Xiaofeng
-
p. 23579 - 23588
(2019/08/12)
-
- Mechanochemical preparation of hydantoins from amino esters: Application to the synthesis of the antiepileptic drug phenytoin
-
The eco-friendly preparation of 5- and 5,5-disubstituted hydantoins from various amino ester hydrochlorides and potassium cyanate in a planetary ball-mill is described. The one-pot/two-step protocol consisted in the formation of ureido ester intermediates, followed by a base-catalyzed cyclization to hydantoins. This easy-handling mechanochemical methodology was applied to a large variety of α- and β-amino esters, in smooth conditions, leading to hydantoins in good yields and with no need of purification steps. As an example, the methodology was applied to the "green" synthesis of the antiepileptic drug Phenytoin, with no use of any harmful organic solvent.
- Konnert, Laure,Reneaud, Benjamin,De Figueiredo, Renata Marcia,Campagne, Jean-Marc,Lamaty, Frdric,Martinez, Jean,Colacino, Evelina
-
p. 10132 - 10142
(2015/02/19)
-
- Transfer hydrogenation as a redox process in nucleotides
-
Using a combined theoretical and experimental strategy, the heats of hydrogenation of the nucleotide bases uracil, thymine, cytosine, adenine, and guanine have been determined. The most easily hydrogenated base is uracil, followed by thymine and cytosine. Comparison of these hydrogenation enthalpies with those of ketones and aldehydes derived from sugar models indicates the possibility of near-thermoneutral hydrogen transfer between uracil and the sugar phosphate backbone in oligonucleotides. (Figure Presented)
- Achrainer, Florian,Emel'yanenko, Vladimir N.,Tantawy, Waled,Verevkin, Sergey P.,Zipse, Hendrik
-
p. 10426 - 10429
(2015/04/14)
-
- PROCESS FOR STRAIGHTENING KERATIN FIBRES WITH A HEATING MEANS AND DENATURING AGENTS
-
The invention relates to a process for straightening keratin fibres, comprising: (i) a step in which a straightening composition containing at least two denaturing agents is applied to the keratin fibres, (ii) a step in which the temperature of the keratin fibres is raised, using a heating means, to a temperature of between 110 and 250° C.
- -
-
-
- DIHYDROURACIL COMPOUNDS AS ANTI-ICTOGENIC OR ANTI-EPILEPTOGENIC AGENTS
-
Methods and compounds useful for the inhibition of convulsive disorders, including epilepsy, are disclosed. The methods and compounds of the invention inhibit or prevent or treat ictogenesis, epileptogenesis, or epileptogenesis-associated conditions. Methods for preparing the compounds of the invention are also described. Particularly preferred compounds of the invention include Formula 1 as described herein.
- -
-
-
- Hydroxyl radical-induced cross-linking of thymine and lysine: Identification of the primary structure and mechanism
-
Hydroxyl radical-induced formation of a cross-link of thymine (Thy) and lysine (Lys) in the γ-radiolysis of N2O-saturated aqueous solution was studied. A Thy-Lys cross-link (I) of the formal structure that OH radical and 4-carbon-centered Lys radical added respectively to C(5) and C(6) positions of Thy was isolated by a preparative HPLC and identified by a FAB-HRMS. The primary cross-link I was dehydrated by treatment with HCl at 120°C to yield the secondary structure (II) possessing a C(5)-C(6) double bond in the Thy moiety: the latter structure II was reported previously (Dizdaroglu, M.; Gajewski, E. Cancer Res. 1989, 49, 3463-3467). A pulse radiolysis study with a redox titration method indicated that 4-carbon centered Lys radical intermediate was of neutral redox reactivity in contrast to reducing reactivity of 5-hydroxy-5,6-dihydrothymin-6-yl radical intermediate. The cross-link I could be formed by a conventional radical recombination mechanism, but not by an ionic recombination mechanism involving a redox reaction between the radical intermediates.
- Morimoto, Syota,Hatta, Hiroshi,Fujita, Shin-Ichi,Matsuyama, Tomochika,Ueno, Toru,Nishimoto, Sei-Ichi
-
p. 865 - 870
(2007/10/03)
-
- Photoinduced reduction of thymine and uracil derivatives by hypophosphite: Unusual high quantum yield of chromophore loss
-
The quantum yield of chromophore loss of thymine, uracil and their corresponding nucleosides and nucleoside-5′-monophosphates undergoing irradiation with 254 nm UV light was found to be sharply enhanced by hypophosphite; thymine and uracil were reduced by hypophosphite to give 5,6-dihydrothymine and 5,6-dihydrouracil respectively.
- Wang, Kongjiang,Chai, Zhifang
-
p. 1543 - 1544
(2007/10/03)
-
- Reactions of Ni(II) and its complexes with free radicals derived from thymine
-
The effects of nickel(II) ions and its complexes on the products arising from the γ-radiolysis of thymine were studied.The decomposition of the pyrimidine base and formation of different radiolytic products indicate that nickel(II) ions or its complexes have little effect on the radiosensitivity of thymine.The transient hydroxyl adduct of thymine reacts with Ni(II) with the formation of a complex having a nickel-carbon bond.The rate constants for the reactions are of the order of 106 dm3mol-1s-1.Possible mechanisms for the formation of different products in the radiolysis of thymine in the presence of nickel(II) compounds are discussed.
- Chakrabarti, S.,Mandal, P. C.,Bhattacharyya, S. N.
-
p. 307 - 312
(2007/10/02)
-
- Far ultraviolet induced decomposition of thymine in deaerated and aerated aqueous solutions
-
Thymine in aqueous solution was decomposed with quantum yields of 0.3 and 0.4 under N2-saturated and aerated conditions by far-ultraviolet light (>180 nm, far-uv), and quantum yields of 2E-4 and 3E-4 by near-ultraviolet light (>220 nm, near-uv), respectively.The main photolytic products by far-uv were 5,6-dihydrothymine (DHT) (selectivity: S(DHT) = 0.2) and 5-hydroxymethyluracil (HMU) (S(HMU) = 0.1) under N2-saturated conditions. cis- and trans-5,6-Dihydroxy-5,6-dihydrothymine (TG), 6(5)-hydroperoxy-5(6)-hydroxy-5,6-dihydrothymine (HTP) (S(TG) + S(HTP) = 0.2), and N1-formyl-N2-pyruvylurea (FPU) (S(FPU) = 0.4) were obtained under aerated conditions.These products were attributed to the reactions of thymine with the radical H and radical O produced by photolysis of water.
- Ohtani, Bunsho,Nagasaki, Hiroshi,Nishimoto, Sei-ichi,Sakano, Koichi,Kagiya, Tsutomu
-
p. 2297 - 2300
(2007/10/02)
-
- Radiation-induced Reduction of Thymine Derivatives in Aqueous Solution. Part 4. Promoted Transformation of Thymine Glycol into Thymine by Aromatic Amines and Low-valent Transition Metal Salts
-
The radiation induced reduction of thymine glycol in aqueous solution containing sodium formate (pH 7.0) has been studied under deaerated and N2O-satureted conditions at room temperature.For comparison, the radiolysis of (1a) has also been performed with alcohols as a scavenger of OH and H, instead of formate. γ-Irradiation of the deaerated formate solution gave thymine (2), 5,6-dihydrothymine (3), and 6-hydroxy-5,6-dihydrothymine (4) along with a minor product, 5-methylbarbituric acid (5).The radiolytic transformation of (1a) into these products was inefficient under N2O, indicating that CO2- as a primary active species produced by irradiation has much less ability to reduce (1a) compared with e-aq.The presence of either inorganic salts (6a-c) or aromatic amines (7e-f) greatly promoted the total formation of (2) + (3), which depressed those of (4) and (5).The sum of the G values (=molecules/100eV of absorbed energy) of (2) and (3) > increased and that of (4) > decreased, respectively, in the sigmoidal forms with decreasing one-electron oxidation potential of the amines.The ratio G/G increased upon increasing the concentration of o-phenylenediamine (7e).In the absence of added reductants, (6a-e) or (7a-g), the yields of (2) +(3) and (4) changed either with the formate concentration or with variation of alcohols used as radical scavengers.The mechanism involving consecutive one-electron reductions of (1a) and an intermediate 6-hydroxythymin-5-yl radical (8) is discussed and compared with the reduction of 5-bromo-6-hydroxy-5,6-dihydrothymine (1b).
- Nishimoto, Sei-ichi,Ide, Hiroshi,Otsuki, Nobuaki,Nakamichi, Kikumi,Kagiya, Tsutomu
-
p. 1127 - 1134
(2007/10/02)
-
- PHOTOCHEMICAL REACTION BETWEEN TRYPTOPHAN AND THYMINE
-
Irradiation of tryptophan and thymine in aqueous solution produced two photoadducts whose structures were determined by spectral data and X-ray crystallographic analysis.
- Saito, Isao,Sugiyama, Hiroshi,Matsuura, Teruo,Fukuyama, Keiichi,Katsube, Yukiteru
-
p. 3243 - 3246
(2007/10/02)
-
- PROMOTION EFFECT OF 2,2,6,6-TETRAMETHYLPIPERIDINE-1-OXYLS ON THE RADIOLYTIC HYDROXYLATION OF THYMINE IN DEAERATED AQUEOUS SOLUTION
-
Remarkable promotion of the hydroxylation of thymine to give thymine glycol with almost complete depression of side reactions by 2,2,6,6-tetramethylpiperidine-1-oxyl (TMPO.) derivatives was observed in the γ-radiolyses of the N2- and N2O-saturated aqueous solutions.In the O2-saturated solution, TMPO. depressed the thymine conversion close to the level under N2 while promoted the formation of thymine glycol to some extent by decreasing side reactions.
- Kagiya, Tsutomu,Kimura, Ryoji,Komuro, Chikara,Sakano, Koichi,Nishimoto, Sei-ichi
-
p. 1471 - 1474
(2007/10/02)
-
- RADIATION-INDUCED HYDROXYLATION OF THYMINE SENSITIZED BY NITRO COMPOUNDS IN N2O-SATURATED AQUEOUS SOLUTION
-
Hydroxylation of thymine (1) to give thymine glycol (3) is remarkably promoted by the addition of nitro compounds (2a-f) in the γ-radiolysis of the N2O-saturated aqueous solution, although overall decomposition of 1 is depressed to some extent.The G-value of 3 increases linearly with increasing the one-electron reduction potential of 2a-f.
- Wada, Takeshi,Ide, Hiroshi,Nishimoto, Sei-ichi,Kagiya, Tsutomu
-
p. 1041 - 1044
(2007/10/02)
-
