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Abstract

ABSTRACT:The interaction of losartan potassium (LP) with bovine serum albumin (BSA) was studied by fluorescence quenching in combination with UV-Vis spectroscopic method under near physiological conditions. The fluorescence quenching rate constants and binding constants for BSA-LP system were determined at different temperatures. The fluorescence quenching of BSA by LP is due to static quenching and energy transfer. The results of thermodynamic parameters, ∆H (-134.3 kJ mol ) and ∆G (-24.52 to -20.83 kJ mol -1 ), indicated that van der Waals interaction and hydrogen bonding played a major role for LP-BSA association. The competitive experiments demonstrated that the primary binding site of LP on BSA was located at site II in sub-domain IIIA of BSA. The distance between LP and a tryptophane unit was estimated to be 3.183 nm based on the Förster resonance energy transfer theory. The binding constant (Ka) of BSA-LP at 298K was 1.932×104 L mol -1 . Synchronous fluorescence and three-dimensional fluorescence studies showed that the presence of LP could change the conformation of BSA during the binding process.