EFFECTS OF ORIENTATION OF HELICAL ROD AND OF ELECTROST ATIC NATURE OF DYESTUFF ON DIFFUSION IN POLYPEPTIDE MEMBRANE

Abstract

Diffusion of dyestuff in “random oriented” and “oriented” poly (γ-methyl L-glutamate) (PMLG) membranes was studied. In the former membrane, helical rods orient randomly in the palne parallel to the membrane surface. In “oriented” membrane prepared by applying the electric field to EDC solution of PMLG, helical rods orient parallel to both of the membrane surface and electric field. The diffusion of dyestuff observed as the concentration gradient in the membrane, was analysed referring to the gradient calculated on the assumption of concentration dependent diffusion coefficient. This dependence corresponds to the diffusion with Langmuir type adsorption of dyestuff. The coefficient obtained in the direction parallel to the helical rod is a few times larger than that in perpendicular direction. From the geometrical consideration of the diffusion model, it is suggested that the aperture between helical rods is smaller than that obtained by X-ray analysis. Using electropositive Methylene Blue and electronegative Alizarine Red S, the effect of electrostatic nature of dyestuff on the diffusion in slightly electronegative PMLG side chain region was examined. The results suggest that Alizarine Red S may diffuse through a narrow, low affinity region rapidly, Methylene Blue may diffuse slowly through a more broad, high affinity region. This difference is exaggerated when the direction of diffusion is parallel to the helical rod.