Investigation of binding properties of dicationic styrylimidazo[1,2-a]pyridinium dyes to human serum albumin by spectroscopic techniques.

The binding interaction between two dicationic styrylimidazo[1,2-a]pyridinium dyes and human serum albumin (HSA) was investigated at physiological conditions using fluorescence, UV-vis absorption, and circular dichroism (CD) spectroscopies. Analysis of the fluorescence titration data at different temperatures suggested that the fluorescence quenching mechanism of HSA by these dyes was static. The calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) indicated that hydrogen bonding and van der Waals forces played a major role in the formation of the dye-HSA complex. Binding distances (r) between dyes and HSA were calculated according to Förster's non-radiative energy transfer theory. Studies of conformational changes of HSA using CD measurements indicate that the α-helical content of the protein decreased upon binding of the dyes. Copyright © 2016 John Wiley & Sons, Ltd.

Study of Binding Properties Between Two New Ibuprofen and Naproxen Based Acyl Hydrazone Derivatives and Trypsin.

Two acyl hydrazone derivatives, AHI and AHN,made from ibuprofen and naproxen-derived hydrazides, were prepared and studied of binding properties with serine protease trypsin by UV-vis absorption and fluorescence quenching at pH 7.4. The results suggest that both hydrazones can interact strongly with trypsin and there are the formation of trypsin-hydrazone complexes. The Stern-Volmer constants, binding constants,binding sites and the corresponding thermodynamic parameters ΔH°, ΔS° and ΔG° were calculated at different temperatures.The effect of common metal ions on the constants was also discussed. The binding modes can be explained on the basis of hydrogen bonds and van der Waals forces. The binding distance(r) ~3 nm between the donor (trypsin) and acceptors (AHI and AHN) was obtained according to Förster's non-radiative energy transfer theory. Moreover, LOD and LOQ of hydrazones were calculated in the presence of trypsin.