Thermodynamics of Formation of the Triple Helix from Free Chains and from Template-Constrained Chains of Collagen-like Monodisperse Poly(Gly-Pro-Hyp) Structures

Statistical thermodynamic methods, developed for treating the α-helix−coil transition, are applied herein to describe the formation of the triple helix from short free chains and short template-constrained chains of collagen-like monodisperse poly(tripeptides), using poly(Gly-Pro-Hyp) as the example. For such short chains, application of the one-helical-sequence approximation indicates that there is very little unwinding from the ends, so that an all-or-none model is adequate to treat this transition. From the dependence of the helix nucleation and propagation parameters on chain length, concentration, and temperature, the thermodynamic parameters for formation of the triple helix from both free chains and template-constrained monodisperse poly(Gly-Pro-Hyp) chains are similar, and also similar to those for free poly(Gly-Pro-Pro) chains.