ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
At sufficiently high ionic strength, long-range electrostatic interactions in a polyelectrolyte such as poly(L-glutamic acid) might be adequately approximated in matrix calculations by use of statistical weights representing second-order interactions. The validity of this assumption has been investigated making use of experimental observations (CD spectra and titration curves) for poly(L-glutamic acid) as a function of temperature in 0.1-0.5M sodium chloride. Theoretical analysis, using a statistical weight matrix proposed by Warashina and Ikegami, is based on the Zimm-Rice theory. Implementation differs from that of Warashina and Ikegami in one respect. Refinement of the initial estimates is achieved using a form of the configuration partition function which does not assume diagonalization of the statistical weight matrix. This difference is of no consequence for the values of σ and s, but it does produce somewhat different values for the statistical weights used to represent the electrostatic interactions. The method used to treat electrostatic interactions in poly(L-glutamic acid) in 0.1M sodium chloride can be viewed as successful in that it properly reproduces the helix-coil transition and titration curves in this solvent and the molecular-weight dependence of the titration curves yields values for s in harmony with those obtained using a treatment which is independent of model, and gives a reasonable ionic-strength dependence for the electrostatic parameters. Furthermore, the model can account for measured helix-coil transitions and titration curves in homopolypeptides in which the side chain is - (CH2)xNHCO(CH2)yCOOH. The model, however, is not exact. It does not properly account for the molecular-weight dependence of the helical content for polymers of low degree of polymerization.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.1981.360201011
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