The characteristics of the intermediates in collagen-fold formation

The kinetics of collagen-fold formation has been analyzed in terms of a series of consecutive reactions, rather than the usual set of parallel reactions. Data on the regain of optical rotation and viscosity for denatured ichthyocol, formaldehyde cross-linked ichthyocol, isolated α1-chains, α2-chains and the β₁₂-component of rat skin collagen have been utilized. The Guggenheim point averaging procedure was used for data analysis for those reaction steps where final equilibrium measurements cannot be made. By considering the data over appropriate time ranges, optical rotation constants characteristic of each sequential intermediate have been determined. Comparisons of the constants for the first nucleated intermediate in the cases of varying degrees of cross-linking and differing pyrrolidine ring contents, show that both hydrogen-bonding interactions and pyrrolidine ring content contribute to the stabilization of the multistranded nucleated fold intermediate. The presence of single chain nucleated intermediate seems highly unlikely.