Dissociation kinetics of tetra-S-carbamidomethylated plasmin-modified human somatotropin.

The dissociation of tetra-S-carbamidomethylated, plasmin-modified human somatotropin at 25 +/- 2 degrees C has been found to be a slow, exergonic equilibrium reaction; an equilibrium constant of 1.77 mol/L and a standard free energy of dissociation of -340 cal/mol have been calculated. The major products of the dissociation have been shown to consist of a monomeric form of the 51-residue carboxyl-terminal fragment and a trimeric form of the 134-residue amino-terminal fragment. The carboxyl-terminal fragment appears to be a random coil, while the amino-terminal fragment retains a considerable degree of secondary and tertiary structures.