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Determination of the rates and barriers to conformational isomerization in the dipeptide L ‐pro‐ L ‐4hyp by direct 13 C nmr thermal equilibration
Author(s) -
Roques B. P.,
GarbayJaureguiberry C.,
Combrisson S.,
Oberlin R.
Publication year - 1977
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.1977.360160415
Subject(s) - chemistry , dipeptide , isomerization , activation barrier , nucleation , kinetics , aqueous solution , kinetic energy , helix (gastropod) , stereochemistry , crystallography , molecule , catalysis , peptide , organic chemistry , biochemistry , quantum mechanics , ecology , physics , snail , biology
The 13 C nmr equilibration method lends itself as a tool for study of conformational rate processes involving aqueous media in conjunction with high activation barriers. This method is applied for measurement of kinetic and thermodynamic parameters of isomerism in the dipeptide L ‐Pro‐ L ‐4Hyp. The activation barrier for cis ⇋ trans interconversion (ω 0° → 180°) is determined, ΔG ≠ = 22.3 kcal/mol. From low‐temperature study, an upper limit ΔG ≠ < 9.7 kcal/mol is evaluated for cis ′ ⇋ trans ′ rotation (ψ −40° → 160°). These data are compared with computed values found in literature. The results are discussed in connection with the helix–coil transition of collagen involving Gly‐ L ‐Pro‐ L ‐4Hyp as nucleation sites.