  We study the kinetics of helix-coil transition in water solutions of gelatin
(collagen protein) by optical rotation techniques combined with thermal
characterization. By examining the rates of secondary helix folding, and
covering a very wide range of solution concentrations, we are able to identify
a universal exponential dependence of folding rate on concentration and quench
temperature. We demonstrate a new concentration-temperature superposition of
data at all temperatures and concentrations, and build the corresponding master
curve. The results support the concept of a diffuse helix-coil transition. We
find no concentration dependance of the normalized rate constant, suggesting
first order (single) kinetics of secondary helix folding dominate in the early
stages of renaturation.
