Abstract

In the present investigation, we have elucidated the interaction between thionine (TH) and bovine hemoglobin (BHb) under physiological conditions by using absorption, emission, time resolved fluorescence, synchronous fluorescence, circular dichroism (CD) and three dimensional emission (3D) spectral studies. Molecular docking experiment was also carried out to establish the possible binding site of TH on BHb. The emission spectral studies revealed that, TH have the ability to bind with BHb and form a ground state complex via static quenching process. The calculated binding constant and the number of binding sites was found to be 3.65 x 10(4) dm(3) mol(-1) and 1.04, respectively. Forster Resonance Energy Transfer (FRET) theory was employed to calculate the distance (r) between donor (BHb) and acceptor (TH) as 3.64 nm. Furthermore, the conformational changes of BHb induced by TH complexation showed some degree of structural unfolding. In addition, molecular docking study confirmed that the most probable binding site of TH was located within the active cavity constituted by alpha 1 and alpha 2 subunits of BHb. (C) 2014 Elsevier B.V. All rights reserved.