Fluorometric investigation of the interaction between methylene blue and human serum albumin

The interaction between methylene blue (MB) and human serum albumin (HSA) was investigated by fluorescence spectroscopy and UV-vis absorbance spectroscopy. In the mechanism discussion, it was proved that the fluorescence quenching of HSA by NIB is a result of the formation of MB-HSA complex and electrostatic interactions play a major role in stabilizing the complex. The Stern-Volmer quenching constant K-SV and corresponding thermodynamic parameters Delta H, Delta G and Delta S were calculated. Binding studies concerning the number of binding sites n and apparent binding constant K-b were performed by fluorescence quenching method. The distance r between the donor (HSA) and the acceptor (MB) was obtained according to fluorescence resonance energy transfer (FRET). Wavelength shifts in synchronous fluorescence spectra showed the conformation of HSA molecules is changed in the presence of MB. (c) 2005 Elsevier B.V. All rights reserved.