Sedimentation and diffusion studies on insulin: the maximum molecular weight

Abstract

The sedimentation and diffusion characteristics of solns. of crystalline insulin were investigated in the pH range 7-8; the variation of diffusion coefficient with concn. and pH confirms the evidence of dissociation advanced from other studies. Temp. change within the range 14-30[degree] has no apparent effect on the dissociation equilibrium. The substance is apparently stable in the range pH 7.0-7.4 and at concns.greater than 0.3 g./l00 ml. Under these conditions the sedimentation constant is 3.12 and the diffusion coefficient about 8.2. These values differ from previously accepted values. The diffusion and sedimentation results were combined to give a max. molecular wt. of about 36,000 for this protein, in agreement with X-ray data on the solid substance.