Fluorescence-labeled synthetic glycopolymers: a new type of sugar ligands of lectins

Radical copolymerization of a polymerizable dansyl derivative, N-2-propenyl-(5-dimethylamino)-1-naphthalene sulfonamide, with sugar monomers and acrylamide proceeded smoothly in aqueous solution in the presence of ammonium persulfate and N,N,N',N'-tetramethylethylenediamine and afforded a novel type of water-soluble glycopolymers having fluorescent side-chains. Fluorescence emission spectra of these polymeric sugar-ligands by excitation at 340 nm revealed maxima at 448 and 528 nm. When the glycopolymer carrying galactose residues was saturated with Ricinus communis agglutinin (RCA60), the fluorescence emission maxima at 448 and 528 nm were not shifted significantly, although the fluorescence intensities were decreased by 20 and 14%, respectively. Polymeric sugar-cluster effects drastically enhanced the association constants of galactose residues with RCA60 in the order of 10(8) M-1. The significance for efficient binding of galactose density on the glycopolymer was also demonstrated by using glycopolymers with different degrees of galactose branching.