Fluorometric probing on the binding of hematoxylin to serum albumin

Abstract

The binding of a cell nucleus stain, hematoxylin (HTL), to bovine serum albumin (BSA) was studied by spectroscopy including fluorescence spectra, UV-Visible absorption, circular dichroism (CD) spectra, synchronous and three-dimensional fluorescence spectra. The results indicated that the binding had led to static fluorescence quenching, with non-radiation energy transfer happening within single molecule. The observed binding constant was calculated to be 10(5.588) l mol(-1) at 311 K and one binding site had formed. The thermodynamic parameters of the interaction complied with DeltaG (theta) < 0, DeltaH (theta) < 0, DeltaS (theta) < 0 and the results indicate that hydrogen bonds played major role in the reaction. The distance r between donor (BSA) and acceptor (HTL) was obtained according to the Förster theory of non-radiation energy transfer. The structural change of BSA molecules with addition of HTL was analyzed and the optimized geometry of HTL-BSA was investigated by fluorescence probe method.