Bromocresol green as a new spectrophotometric probe for serum albumins

Bromocresol green (BCG) has been employed as a new spectrophotometric probe to characterise the binding regions of human serum albumin (HSA) and bovine serum albumin (BSA). BCG binds with greater affinity onto BSA than onto HSA. Based on the abilities of ligands Naproxen and l-anilino-8-naphthalenesulphonic acid (ANS) to displace BCG from the serum albumins by competitive or non-competitive mechanism, binding regions were identified for these ligands. It has been found that both Naproxen and ANS share common binding sites with BCG in HSA with the relative ability of Naproxen > ANS on binding to HSA. In the case of BSA, ANS competes with BCG for the same binding sites, whereas Naproxen exhibits non-competitive binding. The highaffinity sites of Naproxen coincide with BCG binding sites while the low-affinity sites occur at sites distinct from the BCG binding region.