Further studies on the denaturation of arachin with urea and guanidinium chloride

Solubility, sedimentation velocity, viscosity, osmotic pressure, and end-group analysis techniques have been employed to study further the denaturation of arachin with urea and guanidinium chloride. On denaturation with the latter reagent, arachin is divided into two distinct fractions, one fraction (ca. 80%) being insoluble and the other soluble in I = 0.2, pH = 8 buffer. The insoluble fraction is a highly viscous material of molecular weight ca. 30,000 and with N-terminal residues similar to those in native arachin, whereas the soluble fraction is considerably less viscous and of much lower molecular weight. In the case of urea, the material originally insoluble in I = 0.2, pH = 8 buffer is gradually solubilized after long times of exposure to urea, scission of peptide linkages occurring as indicated by the increase in the number of N-terminal residues.