Interaction between thebaine and bovine serum albumin

The binding reaction between thebaine (TB) and bovine serum albumin (BSA) was studied by fluorescence and absorption spectrometry. It is shown that there is a powerful ability in TB to quench the fluorescence intensity of BSA, and there is an overlap between the fluorescence spectrum of BSA and the absorption spectrum of TB. The results also indicated that TB could bind with BSA strongly at molar ratio 1: 1 and the equilibrium constant were 3.76 x 10(5). The action distance (r = 2.95 nm) between donor (BSA) and acceptor (TB) was calculated according to Forster's nonradiative energy transfer mechanism. The thermodynamic parameters indicate that TB molecule combines with BSA through the electrostatic force.