N 10 N-(2-Carboxyethyl)chitosans: Regioselective synthesis, characterisation and protolytic equilibria [Text] / Yu. A. Skorik, C. A. R. Gomes, M. T.S.D. Vasconcelos, Yu. G. Yatluk // Carbohydrate Research. - 2003. - Vol. 338, № 3. - P271-276 Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): CARBOXYETHYLATION POLYSACCHARIDES -- N-(2-CARBOXYETHYL)CHITOSAN -- POLYAMPHOLYTE Аннотация: N-(2-Carboxyethyl)chitosans were obtained by reaction of low molecular weight chitosan with a low degree of acetylation and 3-halopropionic acids under mild alkaline media (pH 8-9, NaHCO3) at 60°C. The chemical structure of the derivatives obtained was determined by 1H and 13C NMR spectroscopies. It was found that alkylation of chitosan by 3-halopropionic acids proceeds exclusively at the amino groups. The products obtained are described in terms of their degrees of carboxyethylation and ratio of mono-, di-substitution and free amine content. The protonation constants of amino and carboxylate groups of a series of N-(2-carboxyethyl)chitosans were determined by pH-titration at ionic strength 0.1 M KNO3 and 25°C. © 2002 Elsevier Science Ltd. All rights reserved. |
C 74 Complexation models of N-(2-carboxyethyl)chitosans with copper(II) ions [Text] / Yu. A. Skorik, C. A. R. Gomes, N. V. Podberezskaya, G. V. Romanenko, L. F. Pinto, Yu. G. Yatluk // Biomacromolecules. - 2005. - Vol. 6, № 1. - P189-195 . - ISSN 1525-7797 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: The copper(II) complex formation equilibria of N-(2-carboxyethyl)chitosans with three different degrees of substitution (DS = 0.42, 0.92, and 1.61) were studied in aqueous solution by pH-potentiometric and UV-spectrophotometric techniques. It was demonstrated that the complexation model of CE-chitosans depends on DS: the [Cu(Glc-NR2)2] complexes are predominant for two lower substituted samples ("bridge model", log ?12 = 10.06 and 11.6, respectively), whereas the increase of DS leads to formation mainly of the [Cu(Glc-NR2)] complexes ("pendant model", log ?11 = 6.41). As a model for copper complexation with a disubstituted residue of CE-chitosan, the complex of N-methyliminodipropionate [CuMidp(H2O)]·(H2O) was synthesized and structurally characterized by XRD. The unit cell consists of two crystallographically nonequivalent Cu atoms having slightly distorted square pyramidal coordination; Midp constitutes the basal plane of the pyramid and acts as a tetradentate NO3 chelate-bridging ligand by the formation of two six-membered chelate rings (average Cu-O 1.99 A, Cu-N 2.04 A) and a bridge via carbonyl O atom (average Cu-O 1.99 A), an apical position is occupied by a water molecule (average Cu-Ow 2.30 A). |
N 10 N-alkylation of chitosan by beta-halopropionic acids in the presence of various acceptors [Text] / A. V. Pestov, Yu. A. Skorik, G. Kogan, Yu. G. Yatluk // Journal of Applied Polymer Science . - 2008. - Vol. 108, № 1. - P119-127 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: N-carboxyethylation of chitosan by -halopropionic acids in the presence of various proton and halogen ion acceptors was investigated. It has been observed that carboxyethylation of chitosan in aqueous medium is accompanied by the by-processes of hydrolysis and dehydrohalogenation of the -halopropionic acids yielding -hydroxypropionic acid, bis(2-carbox-yethyl) ether, and acrylic acid. Degree of carboxyethyl substitution (DS) of chitosan and the relative rates of the by-processes varied significantly depending on the conditions used and nature of the proton or halogen ion acceptor. At carboxyethylation of chitosan with the alkaline -bromopropionates, the DS increased in the order Cs+ Rb- K+ sim; Na+ Li-. |
A 62 Antioxidant and antimutagenic activity of N-(2-carboxyethyl)chitosan [Text] / G. Kogan, Yu. A. Skorik, I. Zitnanova, L. Krizkova, Z. Durackova, C. A. R. Gomes, Yu. G. Yatluk, J. Krajcovic // Toxicology and Applied Pharmacology . - 2004. - Vol. 201, № 3. - P303-310 : ил. - Библиогр.: с. 309-310 (49 ref.) Рубрики: ХИМИЧЕСКИЕ НАУКИ Кл.слова (ненормированные): CARBOXYETHYLATION -- CHITOSAN -- EUGLENA GRACILIS -- OFLOXACIN -- ANTIOXIDANT -- ANTIMUTAGENICITY Аннотация: The antioxidant and antimutagenic activities of the novel carboxyethyl derivatives of chitosan with three different degrees of substitution have been assayed in vitro in the unicellular flagellate Euglena gracilis subjected to the action of genotoxic agents acridine orange and ofloxacin. It has been demonstrated that chitosan derivatives exhibit concentration-dependent protective antigenotoxic activity against both mutagens. It is suggested that different mechanisms may be involved in its protective action—antioxidant activity in case of ofloxacin-induced DNA damage, as well as possible interaction with the cell membrane that prevents acridine orange from reaching the genetic compartments and subsequent damaging DNA through intercalative binding. Direct adsorption of acridine orange on chitosan derivatives was ruled out as a possible mechanism of protection on the basis of spectrophotometric measurements. Dependence of the antimutagenic properties of the studied chitosan derivatives on the degree of substitution was reversed in experiments involving acridine orange and ofloxacin, which also indicated different mechanisms of protection involved in these two cases.???? |
M 57 Mercury sorption on a thiocarbamoyl derivative of chitosan [Text] / K. C. Gavilan, A. V. Pestov, H. M. Garcia, Yu. G. Yatluk, J. Roussy, E. Guibal // Journal of Hazardous Materials. - 2009. - Vol. 165, № 1-5. - P415-426 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: The grafting of thiourea on chitosan backbone allows synthesizing a thiocarbamoyl derivative that was very efficient for mercury sorption in acidic solutions. Though the sorption capacity is not increased compared to raw chitosan in near neutral solutions, this modification allowed maintaining high sorption capacity (close to 2.3 mmol Hg g-1) at pH 2. Mercury sorption in acidic solutions is not affected by the presence of competitor metals (such as Zn(II), Pb(II), Cu(II), Cd(II), Ni(II)) or the presence of nitrate anions (even at concentration as high as 0.8 M)). The presence of chloride or sulfate anions (0.8 M) decreased Hg(II) sorption capacity to 1 mmol Hg g-1. Kinetics are controlled by a combination of pseudo second-order reaction rate and resistance to intraparticle diffusion. Mercury desorption reached about 75% using thiourea (in HCl solution) \\\\Expert2\\nbo\\Journal of Hazardous Materials\\2009, v.165.p.415.pdf |
H 43 Heavy metals removal by flocculation/precipitation using N-(2-carboxyethyl)chitosans [Text] / S. YU. Bratskaya, A. V. Pestov, Yu. G. Yatluk, V. A. Avramenko // Colloids and Surfaces A: Physicochemical and Engineering Aspects. - 2009. - Vol. 339, № 1-3. - P140-144 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: Here we report on solution properties and flocculation performance of polyampholyte chitosan derivatives - N-carboxyethylated chitosans (CEC) - synthesized "in gel" by treatment of chitosan with acrylic acid. We show that carboxyethylation with the substitution degrees (DS) from 0.7 to 1.6 yields water-soluble derivatives, whose isoelectric points (IEP) range from 6.30 to 3.55. At pH 7.5 interaction of negatively charged CEC derivatives with positively charged colloids of the heavy metal hydroxides (Zn2+, Cu2+, Ni2+), serving as a model of postgalvanic wastewaters, results in lowering of electrokinetic potential of the hydroxide colloids and their precipitation at appropriate flocculant dose. Investigations of CEC flocculation performance depending on pH and DS show that the efficiency of metal removal decreases in the row Cu2+ Zn2+ Ni2+ corresponding to the row of the hydroxocomplex stability for these metals. The higher was pH of the system and DS of CEC derivative, the narrower was the flocculation window and the stronger was negative effect of flocculant overdosing on the efficiency of heavy metal removal. Based on the estimation of floc settling rates and the residual metal concentrations, we have concluded that the optimal DS of CEC derivatives for the precipitation of metal hydroxides is 0.7-1.0 |
P 49 Pestov, A. V. In-gel carboxyethylation of chitosan by beta-halopropionic acids [] : доклад, тезисы доклада / A. V. Pestov, Yu. A. Skorik, Yu. G. Yatluk // 10-th International Conference on Chitin and Chitosan - 7th International Conference of the European Chitin Society, Le Corum, Montpellier, France, 6-9 September 2006 : book of abstracts . - Le Corum, Montpellier (France), 2006. - 76 (PC 11) Рубрики: ХИМИЧЕСКИЕ НАУКИ |
P 49 Pestov, A. V. Triocarbaamoylation of chitosan [] : доклад, тезисы доклада / A. V. Pestov, Yu. A. Skorik, Yu. G. Yatluk // 10-th International Conference on Chitin and Chitosan - 7th International Conference of the European Chitin Society, Le Corum, Montpellier, France, 6-9 September 2006 : book of abstracts . - Le Corum, Montpellier (France), 2006. - 76 (PC 12) Рубрики: ХИМИЧЕСКИЕ НАУКИ |
Y 32 Yatluk, Yu. G. Novel unique reagent for preparation of carboxyethyl chitosan-beta-acryloyloxyproprionic acids [] : доклад, тезисы доклада / Yu. G. Yatluk, A. V. Pestov, Yu. A. Skorik // 10-th International Conference on Chitin and Chitosan - 7th International Conference of the European Chitin Society, Le Corum, Montpellier, France, 6-9 September 2006 : book of abstracts . - Le Corum, Montpellier (France), 2006. - 77 (PC 13) Рубрики: ХИМИЧЕСКИЕ НАУКИ |
S 73 Sorption properties of the modified chitin-glucans [] : доклад, тезисы доклада / M. A. Yurovskikh, A. V. Pestov, G. Kogan, Yu. A. Skorik, Yu. G. Yatluk // Proceedings of the 7th Asia-Pacific Chitin and Chitosan Symposium "Advances in chitin science and technology", Bexco, Busan, Korea, 23-26 April 2006. - Handrimwon, 2006. - С. 60-62. - Библиогр.: с. 61 (2 ref.) Рубрики: ХИМИЧЕСКИЕ НАУКИ |
P 49 Pestov, A. V. In-gel synthesis of N-(2-carboxyethyl)chitosan [] : доклад, тезисы доклада / A. V. Pestov, Yu. G. Yatluk, Yu. A. Skorik // Proceedings of the 7th Asia-Pacific Chitin and Chitosan Symposium "Advances in chitin science and technology", Bexco, Busan, Korea, 23-26 April 2006. - Handrimwon, 2006. - С. 90-91. - Библиогр.: с. 91 (9 ref.) Рубрики: ХИМИЧЕСКИЕ НАУКИ |
C 77 Coordinational polymers on basis of chitosan and fluoricontaining lithium 1,3-diketonates [] : доклад, тезисы доклада / V. I. Filyakova, A. V. Pestov, N. S. Boltacheva, Yu. G. Yatluk, V. N. Charushin // XXIV Международная Чугаевская конф. по координационной химии и Молодежная конф.-шк. "Физико-химические методы в химии координационных соединений", СПб, 15-19 июня 2009 г. : тез. докл. - СПб., 2009. - С. 606-607 Рубрики: ХИМИЧЕСКИЕ НАУКИ |
Х 37 Хемоселективное карбоксиэтилирование хитина и хитозана и антимутагенная активность N-(2-карбоксиэтил)хитозанов [] = Chemoselective carboxyethylation of chitin and chitosan and antimutagenic activity of the reaction products : доклад, тезисы доклада / Ю. А. Скорик, Г. Коган, Л. Крижкова, Ю. Г. Ятлук, А. В. Пестов, К. А.Р. Гомеш, Ю. Крайчович // Современные перспективы в исследовании хитина и хитозана : материалы VII Международной конф., СПб, 15-18 сент. 2003 г. : докл. . - СПб., 2003. - С. 46-50. - Библиогр.: с. 50 (11 назв.) Рубрики: ХИМИЧЕСКИЕ НАУКИ |
С 81 Стоматологические материалы на базе хитозана и карбоксиэтилхитозана [] = Stomatologic materials to base chitosan and carboxyethylchitosan : доклад, тезисы доклада / А. В. Пестов, Ю. А. Бондарь, Т. Д. Мирсаев, Ю. А. Скорик, Ю. Г. Ятлук // Современные перспективы в исследовании хитина и хитозана : материалы VIII Международной конф., Казань, 12-17 июня 2006 г. : докл. - Казань, 2006. - С. 233-235. - Библиогр.: с. 235 (6 назв.) Рубрики: ХИМИЧЕСКИЕ НАУКИ |
P 49 Pestov, A. V. Synthesis in a gel as a new procedure for preparing carboxyethyl chitosan [Electronic resource] / A. V. Pestov, N. A. Zhuravlev, Yu. G. Yatluk // Russian Journal of Applied Chemistry. - 2007. - Vol. 80, № 7. - P1154-1159. - Bibliogr. : p. 1159 (14 ref.) Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: A fundamentally new procedure of synthesis of carboxyethyl chitosan in a physical gel, ensuring higher degree of substitution at lower temperatures and lower consumption of time and chemicals, compared to the existing procedures, was developed. The structure of the resulting products was examined by diffuse reflection IR and 1H NMR spectroscopy in solutions and also 1H and 7Li broad line NMR \\\\Expert2\\nbo\\Russian Journal of Applied Chemistry\\2007, v. 80, N. 7, p.1154.pdf |
S 95 Suvorova, A. L. Polysaccharide derivatives as base for hybride membranes [Text] : реферат / A. L. Suvorova, I. S. Tyukova, A. L. Suvorov // ACHEMA 2009. 29-th International Exhibition-Congress on Chemical Engineering, Environmental Protection and Biotechnology, Frankfurt am Main, 11-15 May 2009. : book of abstr. . - Frankfurt am Main, 2009. - P45
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C 31 Catalytic activity and electrochemical properties of chitosan-containing materials [Text] : реферат / E. G. Kovaleva, A. V. Pestov, A. Mechaev, L. S. Molochnikov, V. Chetina // 6-th Kenya Chemical Society " East and Southern Africa Environmental chemistry", 8-th Theoretical Chemistry in Africa International conference, Kenya, Mombasa, 5-9 Oct. 2009. : вook of abstracts . - Mombasa, Kenya, 2009. - P. 22.
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S 66 Skorik, Yu. A. Evaluation of various chitin-glucan derivatives from Aspergillus niger as transition metal adsorbents [Text] / Yu. A. Skorik, A. V. Pestov, Yu. G. Yatluk // Bioresource Technology . - 2010. - Vol. 101, № 6. - P1769-1775 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: A number of chelating resins were prepared by chemical derivatization of the chitin-glucan (CG) complex isolated from Aspergillus niger biomass, namely chitosan-glucan (CsG), O-carboxymethyl-chitin-glucan (CM-CG), O-(2-sulfoethyl)chitin-glucan (SE-CG), and N-(2-carboxyethyl)chitosan-glucan (CE-CsG). The chemical modification was confirmed by FT-IR and elemental analysis. Nanosecond electron beam irradiation was used to produce insoluble resins and to preserve the reactive functional groups. Batch experiments were carried out to evaluate the adsorption selectivity and capacity of the resins toward transition metal ions (Cu2+, Ni2+, Co2+, Zn2+). The resins showed good adsorption capability with the following selectivity series: Co2+ Ni2+ Cu2+ Zn2+. The total metal adsorption capacities of CG, CsG, CM-CG, SE-CG, and CE-CsG resins at pH 6.5 (ammonium acetate buffer) were found to be 0.205, 0.382, 1.752, 0.319, and 0.350 mmol g?1, respectively. Our results suggest that, depending on the type of chemical modification, the chitin-glucan complexes can be used either for selective Cu2+ removal (CsG) or for total transition metal adsorption (CM-CG) from aqueous effluents |
N 10 N-(2-(2-Pyridyl)ethyl)chitosan (PEC) for Pd(II) and Pt(IV) sorption from HCl solutions [] / L. A. Santos Sorena, M. Ruiz, A. V. Pestov, A. M. Sastre, Yu. G. Yatluk, E. Guibal // Cellulose. - 2010. - 6 December. - Online first : рис., табл. Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: Chitosan was modified by grafting 2-pyridyl-ethyl moieties on the biopolymer backbone for the synthesis of a Platinum Group Metal (PGM) sorbent. The sorbent was tested for Pd(II) and Pt(IV) sorption from HCl solutions. Stable for HCl concentrations below 0.5 M, the sorbent reached sorption capacities as high as 3.2 and 2.6 mmol metal g1 for Pd(II) and Pt(IV), respectively. Metal sorption mainly proceeds by electrostatic attraction in acidic solutions, though a contribution of complexation mechanism cannot be totally rejected. The resistance to intraparticle diffusion is the main controlling mechanism for uptake kinetics. While agitation speed has a limited effect on kinetics, metal concentration and sorbent dosage have a greater effect on the kinetic profiles. The intraparticle diffusivity varies between 3 10?11 and 4.5 1010 m2 min1. Thiourea (combined with HCl solution) is used for Pd(II) and Pt(IV) desorption. The resin could be desorbed and recycled for a minimum of five cycles maintaining high efficiencies of sorption and desorption |
G 34 Gel-synthesis, structure, and properties of sulfur-containing chitosan derivatives [Electronic resource] / A. V. Pestov, O. V. Koryakova, I. I. Leonidov, Yu. G. Yatluk // Russian Journal of Applied Chemistry. - 2010. - Vol. 83, № 5. - P787-794 Рубрики: ХИМИЧЕСКИЕ НАУКИ Аннотация: The possibility of using the thermochemical approach to thermal decomposition of solids, previously developed by the author, to interpretation of the mechanism and kinetics of reduction of metal oxides with hydrogen was studied. Many properties of NiO reduction with hydrogen, including formation of metal nuclea, the nature of induction period, autocatalysis effect, equimolar and isobaric periods of reduction, the character of the effect of hydrogen pressure on reduction rate, and the nanocrystalline structure of a reduced metal, were explained in terms of the given approach \\\\Expert2\\nbo\\Russian Journal of Applied Chemistry\\2010, v. 83, N 5, p.787.pdf |