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Enthalpy of helix–coil transition from heat of solutions. III. Poly‐ N ‐δ‐carbobenzoxy‐ L ‐ornithine and poly‐ N ‐γ‐carbobenzoxy‐ L ‐α,γ‐aminobutyric acid
Author(s) -
Giacometi G.,
Turolla A.,
Verdini A. S.
Publication year - 1972
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.1972.360110116
Subject(s) - chemistry , dichloroacetic acid , enthalpy , helix (gastropod) , side chain , electromagnetic coil , random coil , thermodynamics , crystallography , polymer , organic chemistry , circular dichroism , ecology , physics , biology , snail , electrical engineering , engineering
The helix‐to‐coil transition in dichloroethane–dichloroacetic acid (DCE–DCA) mixtures for poly‐ N ‐δ‐carbobenzoxy‐ L ‐ornithine (PCBO) and for poly‐ N ‐γ‐carbobenzoxy‐ L α,γ‐aminobutyric acid (PCBBA) have been studied by ORD and the “heat of solution” method. The results provide strong evidence for the existence of a very specific side‐chain/side‐chain interaction in PCBBA, which is discussed on the basis of a detailed structural model. The main sources of enthalpy and entropy changes in helix‐coil transitions of uncharged homopolypeptides in DCE–DCA mixtures are also discussed briefly.