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1

Digitale Medien

Optical rotatory dispersion of E. coli ribosomes and their constituents (1967)

Sarkar, P. K. ; Yang, J. T. ; Doty, Paul

New York : Wiley-Blackwell

Biopolymers 5 (1967), S. 1-4

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ISSN: 0006-3525

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Investigations have been made on the optical rotatory dispersion properties of E. coli ribosomes and their constituent RNA and proteins. The results indicate that (1) no conformational changes are involved in the formation of a 70S particle from the 50S and 308 subunits, (2) the E. coli ribosomal proteins are similar to most globular proteins with little α-helix content, and (3) the conformation of RNA and proteins inside the ribosome is very similar to that in the free state.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bip.1967.360050102

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2

Digitale Medien

Heavy metal binding to heparin disaccharides. II. First evidence for zinc chelation (1992)

Whitfield, Dennis M. ; Sarkar, Bibudhendra

New York : Wiley-Blackwell

Biopolymers 32 (1992), S. 597-619

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ISSN: 0006-3525

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: To map out the heavy metal binding sites of iduronic acid containing oligosaccharides isolated from human kidneys, we studied Zn (II) binding by nuclear magnetic resonance (NMR) and molecular modeling to two disaccharides isolated after nitrous acid depolymerization of heparin and two synthetic disaccharides representative of the heparin structure, namely, IdopA2S(α1,4) AnManOH, 1a, IdopA2S(α1,4)AnManOH6S, 1b, IdopA2S-(α1,4) GlcNSαMe, 2a, and IdopA2S(α1,4)GlcNS6SαMe, 2b (see previous article in this series). A conformational analysis of the metal free and metal bound solutions was made by comparing calculated 〈(NOE)〉s, 〈T1〉s, and 〈J〉s to experimental values. The 1C4, 4C1, and 2S0 conformations of the L-idopyranosiduronate ring and the 4E and 4T3 of the anhydro-D-mannitol ring are evaluated as are rotations about the C5-C6 hydroxymethylene of the AnManOH (6S) or GlcNS(6S) residues. The NOE between IdopA2S H1 and H3 and the known NOE between H2 and H5, as well as the T1 of IdopA2S H3, are introduced as NMR observables sensitive to the IdopA2S ring conformation. Similarly, a NOE between IdopA2S H5 and AnManOH (6S) or GlcNS (6S) H3 was observed that directly restricts the allowed interglycosidic conformational space. For all disaccharides, the Zn(II) bound spectral data are consistent with models in which these motions are partially “frozen” such that the 1C4 conformation of the IdopA2S is stabilized along with the 4T3 conformation of the AnManOH (6S) ring. The interglycosidic conformation is also stabilized in one of two minima. Electrostatic potential energy calculations gave the best overall agreement with experiment and suggest metal binding conformations with the carboxylate and ring oxygen of the IdopA2S residues (1C4 conformation) and either O3 of the GlcNS (6S) residues or the sulfate oxygens of the 6-sulphate for 2b providing additional chelating sites. These chelation models concur with the observation of marked 13C and 1H NMR chemical shifts for the IdopA2S resonances and of GlcNS H3 for 2a and GlcNS6S C6 for 2b. This study of model compounds implicates the IdopA2S(α1,4) GlcNS6S group as part of the heavy metal binding site in biologically important acidic oligosaccharides such as heparin.

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bip.360320604

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3

Digitale Medien

Heavy metal binding to heparin disaccharides. I. Iduronic acid is the main binding site (1992)

Whitfield, Dennis M. ; Choay, Jean ; Sarkar, Bibudhendra

New York : Wiley-Blackwell

Biopolymers 32 (1992), S. 585-596

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ISSN: 0006-3525

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: As model compounds for Ni(II)-binding heparin-like compounds isolated from human kidneys (Templeton, D. M. & Sarkar, B. (1985) Biochem. J. 230 35-42.), we investigated two disaccharides - 4-O-(2-O-sulfo-α-L-idopyranosyluronic acid)-2,5-anhydro-D-mannitol, disodium salt (1a), and 4-O-(2-O-sulfo-α-L-idopyranosyluronic acid)-6-O-sulfo-2,5-an-hydro-D-mannitol, trisodium salt (1b) - that were isolated from heparin after nitrous acid hydrolysis and reduction. The monosulfate (1a) was active whereas the disulfate (1b) was inactive in a high-performance liquid chromatography (HPLC) binding assay with the tracer ions 63Ni(II) 54Mn(II), 65Zn(II), and 109Cd(II). This result is in accord with the isolation of two 67Cu(II) and 63Ni(II) binding fractions from a complete pool of nitrous-acid-derived heparin disaccharides using sulfate gradients and a MonoQ anion exchange column on an FPLC system. One was identified as compound (1a) and the other as a tetrasulfated trisaccharide by high resolution FAB-MS, NMR and HPLC-PAD. Similarly, two synthetic disaccharides - methyl, 2-O-sulfo-4-O-(α-L-idopyranosyluronic acid)-2-deoxy-2-sulfamido-α-D-glucosamine, trisodium salt [IdopA2S(α1,4)GlcNSαMe,2a], and 2-O-sulfo-4-O- (α-L-idopyranosyluronic acid)-2-deoxy-2-sulfamide-6-O-sulfo-α-D-glucosamine, tetrasodium salt [IdopA2S(α1,4) GlcNS6SαMe,2b] - were shown to bind tracer amounts of 63Ni and 67Cu using chromatographic assays. Subsequently, 1H NMR titrations of 1a, 1b, 2a, and 2b with Zn(OAc)2 were analyzed to yield 1:1 Zn(II)-binding constants of 472 ± 59, 698 ± 120, 8,758 ± 2,237 and 20,100 ± 5,598M-1, respectively. The values for 2a and 2b suggest chelation. It is suggested that the idopyranosiduronic acid residue is the major metal binding site. NMR evidence for this hypothesis comes from marked 1H and 13C chemical shift changes to the iduronic acid resonances after addition of diamagnetic Zn(II) ions.

Zusätzliches Material: 7 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/bip.360320603

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4

Digitale Medien

A ceric salt/thiourea redox initiator system for vinyl polymerization (1979)

Pramanick, Dinabandhu ; Chatterjee, Alok Kumar ; Sarkar, Susanta Kumar

New York : Wiley-Blackwell

Die Makromolekulare Chemie 180 (1979), S. 1085-1088

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ISSN: 0025-116X

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/macp.1979.021800430

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5

Digitale Medien

Thermal gelation properties of methyl and hydroxypropyl methylcellulosePresented at the 1977 Annual Meeting of the Institute of Food Technologists, Philadelphia, June 5-8, 1977. (1979)

Sarkar, N.

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 24 (1979), S. 1073-1087

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: Aqueous solutions of methyl and hydroxypropyl methylcellulose are known to gel upon heating. These gels are completely reversible in that they are formed upon heating yet will liquefy upon cooling. The precipitation temperature, gelation temperature, and gel strength of these methylcellulose solutions were determined as a function of molecular weight, degree of methyl and hydroxypropyl substitution, concentration, and presence of additives. The precipitation temperature of these polymer solutions decreases initially with increasing concentration until a critical concentration is reached above which the precipitation temperature is little affected by concentration changes. The incipient gelation temperature decreases linearly with concentration. The strength of these gels is time dependent, increases with increasing molecular weight, decreases with increasing hydroxypropyl substitution, and depends on the nature of additives. Hydrophobe-hydrophobe interaction or micellar interaction is postulated to be the cause of gelation. This thermal gelation property of the polymers is utilized in many end uses including food, pharmaceuticals, ceramics, tobacco, and other industrial applications.

Zusätzliches Material: 10 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1979.070240420

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6

Digitale Medien

Thermal decomposition of potassium persulfate in aqueous solution at 50°C in an inert atmosphere of nitrogen in the presence of acrylonitrile monomer (1988)

Sarkar, Swati ; Adhikari, Mukti Sadhan ; Banerjee, Monoranjan ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 35 (1988), S. 1441-1458

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: The rate of thermal decomposition of persulfate in aqueous solution in the presence of acrylonitrile (AN) monomer (M) and of nitrogen, may be written as: \documentclass{article}\pagestyle{empty}\begin{document}$$ {{ - d\left( {{\rm S}_2 {\rm O}_8^{2 - } } \right)} \mathord{\left/ {\vphantom {{ - d\left( {{\rm S}_2 {\rm O}_8^{2 - } } \right)} {dt{\rm }\alpha }}} \right. \kern-\nulldelimiterspace} {dt{\rm }\alpha }}\left( {{\rm S}_2 {\rm O}_8^{2 - } } \right)^{1.35 \pm 0.05} \times \left( M \right)^{1.26 \pm 0.069} $$\end{document} in the concentration range of persulfate (1.8 to 18.0) ×10-3, and of monomer (M), 0.30 to 1.20, mol dm-3.It was observed that the pH of the solution containing persulfate and monomer did not alter during polymerization if the monomer concentrations were close to its solubility under the experimental conditions. Conductance of the aqueous solutions of persulfate and monomer was found to decrease during the reactions. In an unbuffered aqueous solution containing only persulfate, however, the pH was found to decrease continuously at 50°C with time, while the conductance of the solution was found to increase. The monomer (AN) had no effect on the glass electrodes of the pH meter in aqueous solutions, and also on the electrodes of the conductivity cell. It has been suggested that the secondary or induced decompositions of persulfate were due to the following elementary reactions: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {\left( {\rm X} \right)} \hfill {\rm } {\rm S}_2 {\rm O}_8^{2 - } + M \to \cdot M \hbox{---} {\rm O} \hbox{---} {\rm SO}_3^ - + {\rm SO}_4^{ \cdot ^ - }, \hfill\\ \\ {\left( {\rm Y} \right)} \hfill {\rm } {\rm S}_2 {\rm O}_8^{2 - } + M_j^ \cdot \to M_j \hbox{---} {\rm O} \hbox{---} {\rm SO}_3^ - + {\rm SO}_4^{ \cdot ^ - }, \hfill \\ \\ \end{array} $$\end{document} where (Mj· radicals (j = 1 to 10) are water-soluble oligomeric or polymeric free radicals. kx and ky at 50°C have been estimated as 1.70 X 10-5 and 5.08 × 103 dm3 mol-1 s-1, respectively. By measuring pH of freshly prepared persulfate solutions at 25°C, it is suggested that 0.05-0.30% of persulfate reacts molecularly with water (i.e., hydrolysis), as soon as it (10-3 to 10-2 mol dm-3) is added to distilled water (pH 7.0). This hydrolysis was found to be stopped in dilute sulfuric acid solution (pH 3-4).

Zusätzliches Material: 9 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1988.070350604

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7

Digitale Medien

Persulfate initiated aqueous polymerization of acrylonitrile at 50°C in an inert atmosphere of nitrogen gas (1988)

Sarkar, S. ; Adhikari, M. S. ; Banerjee, M. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Journal of Applied Polymer Science 36 (1988), S. 1865-1876

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ISSN: 0021-8995

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Maschinenbau , Physik

Notizen: The rate of aqueous polymerization (Rp) of acrylonitrile (AN) initiated by potassium persulfate at 50°C, is given by: \documentclass{article}\pagestyle{empty}\begin{document}$$ R_p {\rm }\infty \left( {{\rm S}_2 {\rm O}_8^{2 - } } \right)^{0.47 \pm 0.06} \times \left( {\rm M} \right)^{1.40 \pm 0.059}$$\end{document} where (M) stands for monomer concentrations. It has been suggested that persulfate ions in aqueous solution (pH 4 to 7) decompose not only via the well established paths viz.: (A) and (B) (A)\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm S}_{\rm 2} {\rm O}_8^{2 - } \to 2{\rm SO}_4^{. - } $$\end{document} (B)\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm S}_{\rm 2} {\rm O}_8^{2 - } + {\rm H}_2 {\rm O} \to {\rm HSO}_4^ - + {\rm OH} + {\rm OH} + {\rm SO}_{\rm 4}^{{\rm .} - } ,\left( {{\rm or }2{\rm HSO}_4^ - + \frac{1}{2}{\rm O}_{\rm 2} } \right) $$\end{document} but also via (C) and (D) in the presence of AN monomer: (C)\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm S}_{\rm 2} {\rm O}_8^{2 - } + {\rm M} \to {}^.{\rm M}\hbox{-\hskip-1pt-}{\rm O}\hbox{-\hskip-1pt-}{\rm SO}_3^ - + {\rm SO}_4^{. - } $$\end{document} (D)\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm S}_{\rm 2} {\rm O}_8^{2 - } + \left( {{\rm M}_j^. } \right)_w ,\left( {j = 1{\rm to }10} \right) \to {\rm M}_j\hbox{-\hskip-1pt-}{\rm O}\hbox{-\hskip-1pt-}{\rm SO}_3^ - + {\rm SO}_{\rm 4}^{{\rm . - }} $$\end{document} where (M·j)w is a water-soluble monomeric/oligomeric free radical. The separating polymer phase remains in aqueous solution as a stable colloid, or a precipitate, depending on the ionic strength of the medium. At high conversions in general, and even at low conversions at relatively higher monomer concentrations, (1.20 m/dm3), the colloidal latex polymer was found to have a tendency to form gel, and the viscosity of the medium was found to increase with conversions. The distribution coefficient of the monomer between the polymer and the aqueous phases was found to be (0.50 ± 0.10) at 50°C in the presence and absence of electrolytes (K2SO4 7.5 × 10-3 m/dm3). The termination rate constants in the aqueous phase (ktw) and in the polymer phase (ktp) have been estimated as given below: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{tw} = 5.95 \times 10^{10} ;{\rm and }k_{tp} = 3.83 \times 10^7 ,{\rm in }{{{\rm dm}^3 } \mathord{\left/ {\vphantom {{{\rm dm}^3 } {{{\rm m} \mathord{\left/ {\vphantom {{\rm m} {{\rm s,}}}} \right. \kern-\nulldelimiterspace} {{\rm s,}}}}}} \right. \kern-\nulldelimiterspace} {{{\rm m} \mathord{\left/ {\vphantom {{\rm m} {{\rm s,}}}} \right. \kern-\nulldelimiterspace} {{\rm s,}}}}}$$\end{document} taking kp of Dainton et al. as 6.22 × 04 (dm3/m/s) at 50°C.

Zusätzliches Material: 8 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/app.1988.070360812

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8

Digitale Medien

Studies on some radical transfer reactions by entrapping the radicals as polymer endgroups. III. Reaction of ȮH radical with halide ions (1988)

Pramanick, Dinabandhu ; Sarkar, Jyotish ; Bhattacharyya, Ramanath

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 1457-1463

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ISSN: 0887-624X

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The reactions of OH radical with Cl-, Br-, I-, and F- ions have been studied by entrapping the product radicals as polymer endgroup which have been detected and estimated by the sensitive dye partition technique. The rate constants of the reactions with Br-, Cl-, and F- ions have been determined to be 1.51 × 109, 1.32 × 109, and 0.92 × 109 L mol-1 s-1, respectively at 25°C and pH 1.00. Oxidation of I- ions liberates I, which inhibits the polymerization and the reaction could not be followed by polymer endgroup analysis. The observed order of reactivity Br- 〉 Cl- 〉 F- is in accordance with the electron affinities of the halide ions. The acidity of the reaction medium has a strong influence on the rate of reaction. With Br- ions, the rate constant of the reaction falls from 1.51 × 109 to 0.75 × 109 L mol-1 s-1 at 25°C as the pH is raised from 1.0 to 2.8. The method is simple and accurate and can be applied to study very reactive radicals.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pola.1988.080260517

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9

Digitale Medien

Development of cation exchangers by substitution of phenols with renewable polyphenolic (tannin) materials (1989)

Sarkar, A. ; Mitra, N. C. ; Banerjee, R. S.

New York : Wiley-Blackwell

Journal of Polymer Science: Polymer Letters Edition 27 (1989), S. 331-332

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ISSN: 0887-6258

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Zusätzliches Material: 1 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pol.1989.140270909

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10

Digitale Medien

Studies on some radical transfer reactions by entrapping the radicals as polymer end groups. II. Reactions of ȮH radicals with amino acids (1988)

Pramanick, Dinabandhu ; Sarkar, Jyotish ; Bhattacharyya, Ramanath

Bognor Regis [u.a.] : Wiley-Blackwell

Journal of Polymer Science Part A: Polymer Chemistry 26 (1988), S. 573-581

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ISSN: 0887-624X

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: The reaction of ȮH radicals with a number of aliphatic amino acids has been studied by entrapping the resultant radicals as end groups of poly(methyl methacrylate) that have been detected and estimated by the sensitive dye partition technique. The rate constants of the reaction (in mol-1 L S-1) of 7 amino acids at 25°C and at pH 1.00 have been determined as 8.33 × 108 for glycine, 2.56 × 109 for β-alanine, 2.01 × 109 for β-alanine, 3.99 × 109 for 4-amino butyric acid, 7.56 × 109 for (1+) valine, 1.42 × 1010 for (1-) leucine, and 5.98 × 1010 for 6-amino caproic acid. Glycine, α-alanine, β-alanine, and 4-amino butyric acid produced radicals that underwent deamination and incorporated only carboxyl-bearing end groups in the polymer. The other amino acids, leucine, valine, and 6-amino caproic acid, produced at least two types of radicals, radicals that underwent deamination and those that remained intact, and incorporated in the polymer both carboxyl- and amine-bearing end groups but in different amounts. The latter type of radicals were about 29% from 6-amino caproic acid, 23% from leucine, and 18% from valine. The change of pH from 0.80 to 2.72 did not produce any significant change in the end group profile of the polymer obtained, indicating no appreciable change in the rate of the reaction of ȮH radicals with the simplest amino acid glycine in the pH range studied.

Zusätzliches Material: 4 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/pola.1988.080260220

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