Functional capsule membranes. Part 29. Concanavalin A-induced permeability control of capsule membranes corked with synthetic glycolipid bilayers or grafted with synthetic glycopolymers

Abstract

Large, ultrathin nylon capsule membranes were corked with synthetic glycolipid (2C₁₄-glu and 2C₁₄-gal) or grafted with synthetic polymers having pendant saccharides (Poly-glu and Poly-gal). The permeability of NaCl from the capsule corked with glycolipid bilayers having the α-D-glucopyranosyl head group, but not the β-D-galactopyranosyl head group, was increased by interaction with concanavalin A (Con A) because of the distortion of corking bilayers induced by the specific binding of Con A to the α-D-glucopyranosyl head group on the capsule surface. When the capsule grafted with polymers having pendant α-D-glucopyranosyl units, but not β-D-galactopyranosyl units, was employed, the permeability of water-soluble dyes was reversibly reduced and increased by the alternative addition of Con A and an excess of monosaccharides from outside, respectively. Thus, Con A could specifically form the cross-linked complex with the α-D-glucopyranosyl unit of graft-polymers on the capsule surface and could reduce the permeability. Upon addition of an excess of monosaccharides, Con A was removed from the capsule surface and the permeability reverted to the original fast rate. These permeability changes with Con A largely depend on the molecular size of the permeants. Thus, the lipid bilayers or graft-polymers on the capsule membrane was found to act as a permeation value responding to specific molecular recognition between lectins and carbohydrates on the membrane surface.