Premium
Equilibrium thermal transitions of collagen model peptides
Author(s) -
Persikov Anton V.,
Xu Yujia,
Brodsky Barbara
Publication year - 2004
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1110/ps.03501704
Subject(s) - enthalpy , thermodynamics , triple helix , chemistry , isomerization , relaxation (psychology) , equilibrium unfolding , monomer , isothermal process , thermodynamic equilibrium , protein folding , crystallography , stereochemistry , physics , circular dichroism , organic chemistry , psychology , social psychology , biochemistry , polymer , catalysis
Abstract The folding of collagen in vitro is very slow and presents difficulties in reaching equilibrium, a feature that may have implications for in vivo collagen function. Peptides serve as good model systems for examining equilibrium thermal transitions in the collagen triple helix. Investigations were carried out to ascertain whether a range of synthetic triple‐helical peptides of varying sequences can reach equilibrium, and whether the triple helix to unfolded monomer transition approximates a two‐state model. The thermal transitions for all peptides studied are fully reversible given sufficient time. Isothermal experiments were carried out to obtain relaxation times at different temperatures. The slowest relaxation times, on the order of 10–15 h, were observed at the beginning of transitions, and were shown to result from self‐association limited by the low concentration of free monomers, rather than cis–trans isomerization. Although the fit of the CD equilibrium transition curves and the concentration dependence of T m values support a two‐state model, the more rigorous comparison of the calorimetric enthalpy to the van't Hoff enthalpy indicates the two‐state approximation is not ideal. Previous reports of melting curves of triple‐helical host–guest peptides are shown to be a two‐state kinetic transition, rather than an equilibrium transition.