SOME ASPECTS OF BETA-LACTOGLOBULIN STRUCTURAL-PROPERTIES IN SOLUTION STUDIED BY FLUORESCENCE QUENCHING

The technique of protein fluorescence quenching by acrylamide and sodi um nitrite (NO2-) was used to study some structural aspects of beta-la ctoglobulin in solution. The degree of exposure and the micro-environm ents of the two tryptophanyl residues (Trp-19 and Trp-61) present in t his ruminant milk protein were sensed, and the influence of the pH and the binding of palmitic acid in their accessibilities were analyzed. The results obtained showed that Trp-19 has an accessibility to the qu enchers higher than could be supposed from its structural location. Th e binding of palmitic acid, on the other hand, increases the accessibi lity of both tryptophanyl residues, a fact that could be associated wi th a slight conformational change of the protein. (C) 1998 Elsevier Sc ience B.V. All rights reserved.