Absorption spectra of pyrene in bovine serum albumin and caffeine aqueous solutions

The interactions between pyrene and bovine serum albumin (BSA) and pyrene and caffeine were studied using absorption spectroscopy in aqueous solutions. In the pyrene-BSA system, an equilibrium between free and adsorbed pyrene was observed in the solution. The absorption spectrum of pyrene adsorbed by BSA was obtained. The equilibrium constant was determined to be 1.1x10(6) dm(3) mol(-1). In the presence of caffeine, the absorption spectrum was a superposition of three species; free pyrene and 1:1 and 1:2 pyrene-caffeine complexes. The equilibrium constants were determined to be 820 and 260 dm(3) mol(-1) for the formation reactions of 1:1 and 1:2 pyrene-caffeine complexes respectively.