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  • Polymer and Materials Science  (7)
  • 1
    Electronic Resource
    Electronic Resource
    On expansion of capillary jets of viscoelastic fluids (1960)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 3 (1960), S. 367-368 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1960.070030917
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  • 2
    Electronic Resource
    Electronic Resource
    Conformational changes of poly(L-histidyl-L-alanyl-α-L-glutamic acid) in solution. Transition pathways and conformational intermediates (1979)
    New York : Wiley-Blackwell
    Biopolymers 18 (1979), S. 981-993 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformation and conformational transitions of poly(His-Ala-Glu) have been investigated by ir, nmr, and CD measurements. The results obtained - as well as the results of our previous investigations by potentiometric titration and hydrodynamic techniques [Goren et al., Biopolymers (1977) 16, 1541-1555] - indicate that when dissolved in water, the co-polymer assumes a disordered conformation. On changing the pH of the solution, the states of ionization of the side-chain imidazole and carboxyl groups change in the same manner as in low-molecular-weight model compounds. Concomitantly, the overall shape of the macromolecule is altered, while the conformation of the polypeptide backbone changes from one disordered state to another but never assumes a regular form. In water/methanol and water/trifluoroethanol mixtures, transitions from a disordered state to the α-helix conformation were observed on increasing the alcohol content of the system. The conformational transitions followed pathways which differ from one another according to the experimental conditions employed. Conformational landmarks (intermediates) have been identified along these pathways.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1979.360180416
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  • 3
    Electronic Resource
    Electronic Resource
    Poly(L-histidyl-L-alanyl-α-L-glutamic acid). I. SynthesisFor preliminary reports on studies of poly(His-Ala-Glu), see Ref. 1. (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 2265-2279 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(L-histidyl-L-alanyl-α-L-glutamic acid) has been prepared in order to test the acid-base catalytic ability of a carboxyl-imidazole hydrogen-bonded system. Two different blocked histidyl-alanyl-glutamic acid monomers were used in the polymerization step. The imidazole ring was blocked with either a dinitrophenyl or a t-butyloxycarbonyl group. The γ-carboxyl of glutamic acid was protected as the benzyl ester. Both the coupling reactions and the polymerization step were via the N-hydroxysuccinimide active ester method. Thiolysis removed the dinitrophenyl group, while hydrogen bromide removed the t-butyloxycarbonyl and the benzyl groups. The water-soluble unblocked polymers obtained were fractionated on Sephadex G-50 or Bio-Gel P30. Fractions within a range of average molecular weights of 2,000 to 25,000 were isolated. Enzymatic oxidation of the acid hydrolyzate of the polymers revealed that no detectable racemization had occurred.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360161013
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  • 4
    Electronic Resource
    Electronic Resource
    Poly(L-lysyl-L-alanyl-α-L-glutamic acid)All amino acid are L unless designated otherwise. Other abbreviations are: Dnp, 2,4-dinitrophenyl; Boc, t, butyloxycarbonyl; Cbz, carbobenzoxy; -ONSu, N-hydroxysucinimide ester; Mr, molecular weight; Mw, weight-average moleculer weight; Mn, number-average molecular weight; Mz, z-average molecular weight. (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1513-1525 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(Lys(Cbz)-Ala-Glu(OBzl)) was prepared by the self-condensation of Lys(Cbz)-Ala-Glu(OBzl)-ONSu in dimethylformamide. After deprotection of the side chains, the product was subjected to Sephadex G-50 chromatography. The molecular weight of unfractionated and fractionated poly(Lys-Ala-Glu) was calculated from a calibrated Sephadex G-50 column, spectrophotometrically from Dnp-(Lys-Ala-Glu), equilibrium centrifugation, and viscosity measurements. Approximately 21% of the unfractionated material was polymeric with the remaining 79% being cyclic and monomeric material. Treatment of polymer hydrolysate with L-amino acid and D-amino acid oxidase indicated poly(Lys-Ala-Glu) to be optically pure. The apparent pKa's of the two ionizable groups were 4.1 and 9.7.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160711
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  • 5
    Electronic Resource
    Electronic Resource
    Poly(L-lysyl-L-alanyl-α-L-glutamic acid). II. Conformational studies (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1527-1540 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solution characterization of poly(Lys-Ala-Glu) is described. This polytripeptide is zwitterionic at neutral pH and is shown to take on a conformation which is dictated by the state of ionization, molecular weight, temperature, and solvent. The polypeptide is almost entirely α-helical at low pH and temperature for polymers of greater than 25,000 molecular weight. Melting profiles for these conditions show tm ∼ 20°C. Analysis of circular dichroism curves shows the α-helical content to vary in a linear manner with molecular weight in the range 3000-30,000. At neutral pH the charged polypeptide is essentially random, but substantial α-helix could be induced by addition of methanol or trifluoroethanol. At temperatures where the sequential polypeptide is a random coil, addition of trifluoroethanol produces a polymer which is mostly α-helical but also contains an appreciable ammount of β-structure. The infrared spectrum of a low-molecular-weight fraction assumed to be cyclo(Lys-Ala-Glu)2 was tentatively assigned a β-pleated sheet structure.A comparison of this polytripeptide in various ionization states with other polytripeptides containing L-alanine and L-glutamate or L-lysine shows the α-helix directing properties for the (uncharged) residues to lie in the order Ala 〉 Glu 〉 Lys.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160712
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  • 6
    Electronic Resource
    Electronic Resource
    Viscosity and potentiometric measurements of poly(L-histidyl-L-alanyl-α-L-glutamic acid) and poly(L-lysyl-L-alanyl-α-L-glutamic acid) (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1541-1555 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(His-Ala-Glu) and poly(Lys-Ala-Glu) were examined by viscosity and potentiometric titration. These measurements were interpreted in terms of the hydrodynamic size of the above sequential polypeptides. Effects of polymer, size and concentration, and solution-salt concentration were demonstrated. Although the sequential polypeptides generally behave like polyampholytes, they do demonstrate some differences. These differences my be attributed to the ability of ionized side chains three residues apart to repel themselves, in the order His 〈 Glu 〈 Lys.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160713
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  • 7
    Electronic Resource
    Electronic Resource
    Poly(L-histidyl-L-alanyl-α-L-glutamic acid). II. Catalysis of p-nitrophenyl acetate hydrolysis (1978)
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 1679-1692 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hydrolysis of p-nitrophenyl acetate is catalyzed by imidazole, free in solution or as the side chain in poly(His-Ala-Glu). This is based on the observations that the reaction is first order in ester and first order in nonprotonated imidazole. Catalysis of p-nitrophenyl acetate hydrolysis is dependent on solvent conditions. The effect of low concentrations of ethanol, dioxane, and trifluoroethanol were investigated. As the concentration of organic solvent is increased, the second-order rate constant for imidazole catalysis decreases. The decrease, however, is greater for imidazole than for poly(His-Ala-Glu). In 2% trifluoroethanol/water solution, free imidazole has twice the catalytic activity of polymeric imidazole, while in 40% trifluoroethanol/water they have equal activity. Since under the latter solvent conditions poly(His-Ala-Glu) is partially α-helical, the relative improvement in polymeric-imidazole catalysis may be attributed to imidazole hydrogen-bonded to a carboxylate ion. With this assumption the carboxylate-imidazole hydrogen-bonded system has been calculated to have three times the base catalytic activity of imidazole.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1978.360170706
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