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Helix-coil transition of poly(L-glutamic acid) in N-methylacetamide

✍ Scribed by John B. Harry; James S. Franzen

Publisher
Wiley (John Wiley & Sons)
Year
1969
Tongue
English
Weight
958 KB
Volume
8
Category
Article
ISSN
0006-3525

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✦ Synopsis

The folding of randomly coiled poly(bg1utamic acid) to the helical state has been studied in N-methylacetamide by titration methods. Since this solvent would be expected to form amide-peptide group hydrogen bonds with the unfolded form of the polymer, to a first approximation no helix stabilization could come from intrapolymer hydrogen bonds. The titration data, collected from 30 to 70°C yield the following values per residue for the thermodynamic parameters governing the coil-helix reaction for the uncharged polymer: AGJC, -1.9 f 0.1 kcal; A H", 0 f 0.1 kcal; AS3&, 6.3 f 0.6 eu. In N-methyl acetamide, the helix is an order of magnitude more stable than in water, and this stabilization appears to be entirely the result of the entropy gained by solvent molecules which are released from the polymer upon folding.

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