The recovery of optical rotation and viscosity was followed as a function of temperature and time for α-chain gelatin obtained by denaturation from buffalo fish-swim-bladder ichthyocol and for a γ-gelatin prepared by the denaturation of synthetically cross-linked monodisperse ichthyocol from the same source. Both gelatins had the same pyrrolidine ring content. The rotation recovery was found to be second order in both cases. The viscosity recovery of the γ-gelatin was first order but the kinetics of viscosity recovery were indeterminate in the case of the α-gelatin. The second-order rate constant for rotation recovery was about 30-fold greater for the γ-gelatin than for the α-gelatin at the same concentration and in the same solvent environment. The activation energy was −10 kcal for the γ-gelatin refolding reaction in contrast to −35 kcal for the α-gelatin. An intramolecular refolding mechanism involving the interaction of chain segments of the same molecule is proposed for both gelatins, with cooperative effects and specific interactions providing the driving force for complete renaturation in the case of the γ-gelatins.
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