Abstract: Through the binding with nalidixic acid,bovine serum albumin(BSA)and human serum albumin (HSA) could quench the characteristic fluorescence of nalidixic acid-terbium chelate. Because of the tight binding of phenylbutazone and ibuprofen to the special sites of albumins, they were used as the binding site markers on the albumins, In this paper the different effects of BSAand HSAon the fluorescence of nalidixic acid-terbium chelate were discussed. According to the displacement of the site markers on albumins, the binding site of nalidixic acid on the BSAhas been found to be the Ⅱ special binding site.

Key words: Nalidixic acid, Serum albumins, Terbium ions