Interfacial Recognition of Sugar Residues in Block Copolymers by Lectin As Studied by the Multiple Internal Reflection Fluorescence Method

Macroinitiators were prepared by the coupling of disuccinimidyl ester of 4,4‘-azobis(cyanovaleric acid) with poly(2-methacryloyloxyethyl d-glucopyranoside) (PMEGlc) which had an amino group at its end. Styrene was polymerized with the initiator in the presence of detergent. When the styrene content in the A−B−A block copolymer obtained (PMEGlc-b-PSt-b-PMEGlc) was high, the copolymer made an irreversible entanglement to result in microspheres, whereas the copolymer with a short styrene block could be dispersed monomolecularly. The copolymers dispersed in water were aggregated by mixing with a solution of lectin, Concanavalin A (Con A), due to a specific recognition of glucose moieties in the polymers by the tetrameric lectin. The dispersion of PMEGlc-b-PSt-b-PMEGlc could be deposited to poly(methyl methacrylate) (PMMA) surface to form a polymer layer, in which the PSt blocks might lay on the cuvette and the PMEGlc blocks might direct to the solution phase. The recognition processes of glucose residues in the deposited copolymers by Con A labeled with carboxypentylindocyanine (CPI-Con A) were followed by the multiple internal reflection fluorescence method. The dissociation constant of CPI-Con A with the glucose residue in the copolymer was much smaller than those obtained with α-methyl d-mannopyranoside and α-d-methylglucopyranoside, probably due to the multipoint fixation of CPI-Con A by the surrounding glucose-carrying polymer chains on the cuvette. The usefulness of macroinitiators to prepare various kinds of block polymers which have biorelated functions was strongly suggested.