Binding of bioactive coomassie brilliant blue G with protein: Insights from spectroscopic studies

The binding of CBB to BSA was investigated under imitated physiological conditions employing different optical spectroscopic techniques viz., fluorescence emission, UV-vis absorption and FTIR. Fluorescence quenching data obtained at different temperatures suggested the presence of dynamic type of quenching mechanism. The values of K and n for CBB-BSA system were calculated and found to be 4.20 x 10 4 M -1 and 0.96 respectively, at 302 K. The value of n close to unity indicated that one molecule of CBB bound to one molecule of BSA. The thermodynamic parameters revealed that the hydrophobic forces played a major role in the interaction of CBB with BSA. The distance of separation between CBB and protein was calculated using the theory of FRET. The conformational changes in the secondary structure of BSA upon interaction with the dye were investigated by synchronous fluorescence and FTIR techniques. Competitive binding studies were also carried out to locate the binding site of CBB on BSA. The results of this chapter are published in Scientia Pharmaceutica, 78 (2010) 869-880. Chapter 5 CBB-BSA system 99 Coomassie brilliant blue-G (CBB) Chemical name Benzenemethanaminium, N-[4-[[4[(4-ethoxyphenyl)amino]phenyl][4[ethyl[(3-sulfonyl)methyl]amino] phenyl]methylene]-2,5cyclohexadiene-1-ylidene]-ethyl-3sulfo-monosodium salt