Spectroscopic characterization of effective components anthraquinones in Chinese medicinal herbs binding with serum albumins

Study on interaction of mangiferin to insulin and glucagon in ternary system

The binding of mangiferin to insulin and glucagon was investigated in the presence and absence of another Peptide by optical spectroscopy. Fluorescence titration experiments revealed that mangiferin quenched the intrinsic fluorescence of insulin and glucagon by static quenching. The ratios of binding constants of glucagon-mangiferin to insulin-mangiferin at different temperatures were calculated in "pure" and ternary system, respectively. The results indicated that the Peptides were competitive with each other to act on mangiferin. Values of the thermodynamic parameters and the experiments of pH effect proved that the key interacting forces between mangiferin and the Peptides were hydrophobic interaction. In addition, UV-vis absorption, synchronous fluorescence and Fourier transform infrared measurements showed that the conformation of insulin and glucagon were changed after adding mangiferin.

In vitro study on the binding of anti-coagulant vitamin to bovine serum albumin and the influence of toxic ions and common ions on binding

The mechanism of binding of vitamin K(3) (VK(3)) with bovine serum albumin (BSA) was investigated by fluorescence, absorption and circular dichroism (CD) techniques under physiological conditions. The analysis of fluorescence data indicated the presence of static quenching mechanism in the binding. Various binding parameters have been evaluated. Thermodynamic parameters, the standard enthalpy change, DeltaH(0) and the standard entropy change, DeltaS(0) were observed to be -164.09 kJ mol(-1) and -465.08 J mol(-1)K, respectively. The quantitative analysis of CD spectra confirmed the change in secondary structure of the protein upon interaction with VK(3). The binding average distance, r between the donor (BSA) and acceptor (VK(3)) was determined based on the Förster's theory and it was found to be 3.3 nm. The effects of toxic ions and common ions on VK(3)-BSA system were also investigated.

Ab initio tools for the accurate prediction of the visible spectra of anthraquinones

The UV/vis absorption spectra of 101 anthraquinones solvated in two protic solvents (methanol and ethanol) has been theoretically predicted using the time-dependent density functional theory (TD-DFT) for the excited state calculations and the polarizable continuum model (PCM) for evaluating bulk solvent effects. Two functionals (B3LYP and PBE0) have been used and they provide similar mean absolute deviations (approximately 0.09 eV) but mean signed errors presenting opposite signs. The errors can be minimized by using simple or multiple linear regression, the latter combining the results of both functionals to reach an optimal estimation of the lambda(max) (mean absolute error 0.06 eV). Specific fittings for the two media have been performed and it turned out that our approach is even more efficient for anthraquinones solvated in ethanol.

Interaction of rhein with human serum albumin investigation by optical spectroscopic technique and modeling studies

The binding of rhein with human serum albumin (HSA) has been studied in detail by spectroscopic method including circular dichroism (CD), Fourier transformation infrared spectra (FT-IR), fluorescence spectra. The binding parameters for the reaction have been calculated according to Scatchard equation at different temperatures. The plots indicated that the binding of HSA to rhein at 303, 310 and 318 K is characterized by one binding site with the affinity constant K at (4.93+/-0.16)x10(5), (4.02+/-0.16)x10(5) and (2.69+/-0.16)x10(5) M-1, respectively. The secondary structure compositions of free HSA and its rhein complexes were estimated by the FT-IR spectra. FT-IR and curve-fitted results of amide I band are in good agreement with the analyses of CD spectra. Molecular Modeling method was used to calculate the interaction modes between the drug and HSA.