Protein-sugar interactions: environmental effect on the fluorescence of O-(4-methylumbelliferyl)-glycosides.

We have investigated the effect of 12 solvents and several amino acids on the fluorescence of O-(4-methylumbelliferyl)-glycosides. We showed that: i) the fluorescence quenching is not related to the dielectric constant of the solvents: the fluorescence intensity was maximal in water (d = 80) and in acetic acid (d = 6.2) and was at least ten times lower in acetone (d = 21) and in dioxane (d = 2.2); ii) the fluorescence of O-(4-methylumbelliferyl)-N-acetyl-beta-glucosaminide is not quenched in the presence of various amino acids including arginine, asparagine, aspartate, histidine, leucine, phenylalanine and proline; iii) the fluorescence of O-(4-methylumbelliferyl)-glycoside is quenched by sulfur, phenol and indole amino acids or derivatives containing sulfur, phenol or indole groups. The changes in fluorescence intensities of O-(4-methylumbelliferyl)-glycosides upon binding to concanavalin A, wheat germ agglutinin and lysozyme are discussed with regard to the amino acid content of their binding sites.