Investigating the interaction mechanism of fluorescent whitening agents to human serum albumin using saturation transfer difference-NMR, multi-spectroscopy, and docking studies

Abstract

In this study, 2,2 0 -(4,4 0 -biphenylylenebisvinylene)bisbenzenesulfonicacid (CBS-X) and its disodiumsalt (CBS) were used as model compounds to investigate the interaction mechanism between 4,4 0 -distyrylbiphenyl based fluorescent whitening agents (DSBP-FWAs) and human serum albumin (HSA) through various techniques, including 1 H saturation transfer difference nuclear magnetic resonance ( 1 H STD-NMR), fluorescence studies, UV-vis absorption, Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD) spectroscopy, and molecular docking. The 1 H STD-NMR analyses indicated that CBS and CBS-X can bind to HSA at the favored Sudlow's sites II and I, respectively. Fluorescence emission spectra showed that CBS and CBS-X quenches HSA fluorescence through a dynamic mechanism, and this was further verified by fluorescence lifetime experiments and UV-vis absorption. Moreover, the effective binding constant values of the two compounds at the same temperature decreased in the order CBS > CBS-X. Furthermore, the energy transfer efficiency for CBS and CBS-X were 50.5% and 40.6%, respectively. Thermodynamic analyses indicated that the binding of CBS and CBS-X with HSA are both primarily controlled by hydrophobic forces. FT-IR and CD spectroscopy provided complementary information on the micro-environmental and conformational changes of HSA with the additions of CBS and CBS-X. Molecular docking further confirmed the NMR and spectroscopic results. Overall, the comparative studies on the interaction mechanism of CBS and CBS-X when binding to HSA may provide useful information for evaluating their effects on the human body. Fig. 7 (a) Spectral overlap between the UV-vis absorption spectrum of CBS and the fluorescence spectrum of HSA, (b) spectral overlap between the UV-vis absorption spectrum of CBS-X, and the fluorescence spectrum of HSA. (c) FT-IR spectra of free HSA (I) and spectra of the CBS-HSA system (II) and CBS-X-HSA system (III), with a molar concentration ratio of HSA to CBS (or CBS-X) of 1 : 0.7 in pH 7.4 PBS, [HSA] ¼ 0.2 mM. (d) Circular dichroism spectra of 2 mM HSA in the absence or presence of CBS and CBS-X. Fig. 8 Three-dimensional docking representations for CBS-HSA and CBS-X-HSA interactions. The sites of the interaction of CBS and CBS-X are magnified on the right panel along with the labeling of the HSA residues near the ligands at the interaction site. The H-bonds (green dotted line) are surrounded by a green coil.This journal is

Computational and spectroscopic analysis of interaction between food colorant citrus red 2 and human serum albumin

“…In the present system, K SV values decrease with increasing temperature (Table 1), which indicates that the quenching of HSA by CR might be initiated by complex formation. In other words, specific ground state complexation is responsible for the quenching rather than dynamic collision 27 . Furthermore, this finding was verified through time-resolved fluorescence spectra (Fig.…”

Combination mode of antimalarial drug mefloquine and human serum albumin: Insights from spectroscopic and docking approaches

“…Using Arrhenius plot (inset of Figure B) to determine the activation energy ( E a ), a value of 14.01 kJ mol –1 was obtained for MEF‐HSA system, which was higher than the magnitude for interactions of large number of molecules with protein . In several earlier reports, K a for ligand‐protein interaction has been shown to increase with an increase in temperature …”

Exploring the binding pattern between pepsin and deferasirox using detailed experimental and computer simulation methods

“…The uorescence quenching of pepsin by DFX was a static quenching mechanism, and it was impossible to combine quenching with dynamic and static binding. 21 Moreover, uorescence quenching data at different temperatures can be used to analyze the quenching mechanism. For the dynamic annihilation mechanism, the annihilation process conforms to the dynamic annihilation Stern-Volmer eqn (3).…”