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Helix–coil transition of poly‐γ‐ N ‐carbobenzoxy‐ L ‐α,γ‐diaminobutyrate and poly‐δ‐ N ‐carbobenzoxy‐ L ‐ornithine
Author(s) -
Gaskin Felicia,
Yang Jen Tsi
Publication year - 1971
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.360100404
Subject(s) - dichloroacetic acid , chemistry , optical rotatory dispersion , helix (gastropod) , chloroform , enthalpy , amide , mole , polymer , random coil , crystallography , polymer chemistry , circular dichroism , stereochemistry , thermodynamics , organic chemistry , physics , ecology , snail , biology
The helix–coil transition of poly‐γ‐ N ‐carbobenzoxy‐ L ‐α,γ‐diaminobutyrate (PCLB) and poly‐δ‐ N ‐carbobenzoxy‐ L ‐ornithine (PCLO) in chloroform–dichloroacetic acid mixtures was followed by optical rotatory dispersion. PCLB displays a “normal” temperature‐induced transition, but PCLO an “inverse” one. The thermodynamic parameters for helix formation of the two polymers were determined using the Zimm‐Bragg theory. The enthalpy for adding an amide residue to a helical region, Δ H , and the initiation factor σ were Δ H = −180 cal/mole and σ = 9.2 × 10 −5 for PCLB and Δ H = +490 cal/mole and σ = 1.9 × 10 −5 for PCLO.