Viscosity and potentiometric measurements of poly(<scp>L</scp>‐histidyl‐<scp>L</scp>‐alanyl‐α‐<scp>L</scp>‐glutamic acid) and poly(<scp>L</scp>‐lysyl‐<scp>L</scp>‐alanyl‐α‐<scp>L</scp>‐glutamic acid)

Goren, H. Joseph; Grandan, Loretta; Jay, Alfred W. L.; Lotan, Noah

doi:10.1002/bip.1977.360160713

Biopolymers

1977

DOI: 10.1002/bip.1977.360160713

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Viscosity and potentiometric measurements of poly(L‐histidyl‐L‐alanyl‐α‐L‐glutamic acid) and poly(L‐lysyl‐L‐alanyl‐α‐L‐glutamic acid)

H. Joseph Goren¹,

Loretta Grandan²,

Alfred W. L. Jay³

et al.

Abstract: SynopsisPoly( 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… Show more

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Cited by 5 publications

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Poly(L‐histidyl‐L‐alanyl‐α‐L‐glutamic acid). I. Synthesis

Goren¹,

Katchalski‐Katzir²,

Fridkin³

1977

Biopolymers

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SynopsisPoly(L-histidyl-L-alanyl-a-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 y-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.

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Poly(L‐histidyl‐L‐alanyl‐α‐L‐glutamic acid). I. Synthesis

Goren¹,

Katchalski‐Katzir²,

Fridkin³

1977

Biopolymers

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Poly(L‐histidyl‐L‐alanyl‐α‐L‐glutamic acid). II. Catalysis of p‐nitrophenyl acetate hydrolysis

et al. 1978

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SynopsisThe 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 a-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.

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Conformational changes of poly(L‐histidyl‐L‐alanyl‐α‐L‐glutamic acid) in solution. Transition pathways and conformational intermediates

Goren¹,

Fridkin²,

Katchalski‐Katzir³

et al. 1979

Biopolymers

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SynopsisThe 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 e t al., Biopolymers (1977) 16,1541-15551-indicate that when dissolved in water, the copolymer 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 waterhrifluoroethanol mixtures, transitions from a disordered state to the a-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.

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Viscosity and potentiometric measurements of poly(L‐histidyl‐L‐alanyl‐α‐L‐glutamic acid) and poly(L‐lysyl‐L‐alanyl‐α‐L‐glutamic acid)

Cited by 5 publications

References 17 publications

Poly(L‐histidyl‐L‐alanyl‐α‐L‐glutamic acid). I. Synthesis

Poly(L‐histidyl‐L‐alanyl‐α‐L‐glutamic acid). I. Synthesis

Poly(L‐histidyl‐L‐alanyl‐α‐L‐glutamic acid). II. Catalysis of p‐nitrophenyl acetate hydrolysis

Conformational changes of poly(L‐histidyl‐L‐alanyl‐α‐L‐glutamic acid) in solution. Transition pathways and conformational intermediates

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