HAUSCHKA AND HARRINGTON
Collagen Structure in Solution. 111. Effect of Cross-Links on Thermal Stability and Refolding Kinetics* Peter V. Hauschkat and William F. Harringtont
ABSTRACT : Comparisons of thermal stability and refolding properties are made between two cross-linked collagens (native Ascaris and formaldehyde cross-linked ichthyocol) and their noncross-linked counterparts (RCM-Ascaris and native ichthyocol). The p H dependence of the melting temperature (T,) parallels the ionization of side-chain carboxyl groups. Over the p H range 2.5 to 6, T , increases -5’ for the ichthyocol species and -12” for Ascaris collagen, the larger effect of p H o n the latter material being due to the more even distribution of its ionizable residues throughout the triple-helical structure. Initial rates of renaturation of unfolded collagens showed negative temperature depen-
T
he slow and generally incomplete refolding exhibited by denatured single-chain (a)gelatins is believed t o be a consequence of the extremely small probability of three separate chains becoming aligned in proper register for formation of the triple-helical native collagen structure. At low protein concentrations (
