INTERACTION OF BROMOCRESOL GREEN WITH DIFFERENT SERUM ALBUMINS STUDIED BY FLUORESCENCE QUENCHING

The binding of bromocresol green to bovine serum albumin at micromolar concentrations leads to quenching of protein fluorescence. This prope rty has been used here to study interaction of bromocresol green with bovine serum albumin as a function of pH and ionic strength. The trans formation of fluorescence quench data obtained with bromocresol green into Scatchard plots yielded an association constant of 3.06x10(7) 1M( -1) and a binding capacity of about 1.0. The affinity of bromocresol g reen for bovine serum albumin remains virtually unchanged between pH 4 .0 and 8.0 but decreases by about 7 fold with increase in ionic streng th from 0.01 to 1.0. Six other serum albumins obtained from cat, dog, human, pig and sheep have also been studied for bromocresol green bind ing. Although all the albumins studied bind bromocresol green, they sh ow considerable differences in their affinities towards the dye. It ap pears that despite a great degree of overall similarity in their struc ture and conformation, serum albumins from different species differ in their ligand binding properties.