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Thermal unfolding of helices of a C‐peptide analogue of ribonuclease A in sodium dodecyl sulfate solution
Author(s) -
Wu ChuenShang C.,
Yang Jen Tsi
Publication year - 1990
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360300315
Subject(s) - random coil , chemistry , ribonuclease , crystallography , residue (chemistry) , hydrogen sulfate , helix (gastropod) , sodium dodecyl sulfate , peptide , stereochemistry , physics , circular dichroism , rna , biochemistry , ionic liquid , gene , catalysis , ecology , organic chemistry , biology , snail
The conformation of a 13‐residue C‐peptide analogue of ribonuclease A, \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm suc - A}\mathop {\rm E}\limits^ - {\rm T - AAA}\mathop {\rm K}\limits^{\rm + } {\rm FL}\mathop {\rm R}\limits^{\rm + } {\rm A}\mathop {\rm H}\limits^{\rm + } {\rm A - CONH}_2 $\end{document} , in NaDodSo 4 solutions with respect to temperature was studied with CD. The equilibrium constant of unfolding yielded a straight line in a van't Hoff plot. In 10 m M NaDodSo 4 , Δ G u = 120 cal/mol, Δ H u = 700 cal/mol, and Δ S u = 2.0 entropy units all on per helical residue. These values compared fairly well with the thermodynamic parameters of the uncharged helix‐coil transition of (Glu) n in 0.1 M NaCl based on the theories of Zimm and Bragg and Zimm and Rice. The peptide was not unfolded at 75°C completely. Even in water without surfactant it was not a “random coil.”