Predicting plasma protein binding of drugs: a new approach.

The binding mechanism of molecular interaction between diosmetin and human serum albumin (HSA) in a pH 7.4 phosphate buffer was studied using atomic force microscopy (AFM) and various spectroscopic techniques including fluorescence, resonance light scattering (RLS), UV–vis absorption, circular dichroism (CD), and Fourier transform infrared (FT–IR) spectroscopy. Fluorescence data revealed that the fluorescence quenching of HSA by diosmetin was a static quenching procedure. The binding constants and number of binding sites were evaluated at different temperatures. The RLS spectra and AFM images showed that the dimension of the individual HSA molecules were larger after interaction with diosmetin. The thermodynamic parameters, ΔH° and ΔS° were calculated to be −24.56 kJ mol–1 and 14.67 J mol–1 K–1, respectively, suggesting that the binding of diosmtin to HSA was driven mainly by hydrophobic interactions and hydrogen bonds. The displacement studies and denaturation experiments in the presence of urea indicate...

Probing the binding of the flavonoid diosmetin to human serum albumin by multispectroscopic techniques.

This work used plate height measurements to investigate the kinetics of (R)- and (S)-warfarin binding to an immobilized HSA column. The dissociation rate constants for (R)- and (S)-warfarin on this column increased from 0.06 to 1.9 s-1 and from 0.06 to 0.36 s-1 between 4 and 45 °C. The corresponding association rate constants increased from 2.4 × 104 to 3.2 × 105 M-1 s-1 for (R)-warfarin and from 4.4 × 104 to 7.2 × 104 M-1 s-1 for (S)-warfarin over the same temperature range. From the dissociation data, it was found that an increase in temperature led to a large decrease in the plate height due to stationary phase mass transfer for both enantiomers. Further studies indicated that (R)- and (S)-warfarin had similar activation energies for their binding to HSA. For (R)-warfarin, most of this energy requirement was due to the change in enthalpy of the system, while for (S)-warfarin, it was mainly due to the change in entropy. All of these results agree with an earlier model, in which (R)- and (S)-warfarin wer...

Chiral Separation Mechanisms in Protein-Based HPLC Columns. 2. Kinetic Studies of (R)- and (S)-Warfarin Binding to Immobilized Human Serum Albumin

https://onlinelibrary.wiley.com/doi/pdf/10.1002/chir.20301

Drug binding to human serum albumin: Abridged review of results obtained with high-performance liquid chromatography and circular dichroism

The effect of glycation on the structure, function and biological fate of human serum albumin as revealed by recombinant mutants.

Binding of warfarin to human serum albumin results in a red shift of the UV absorption maximum, suggesting that the binding site is a hydrophobic area of the protein. The enhancement of the fluorescence of warfarin upon binding to human serum albumin was used to study the binding equilibrium and the kinetics of this drug-protein interaction. From equilibrium fluorescence measurements, contributions from free and bound warfarin could be evaluated. From the resulting Scatchard plots, equilibrium constants ranging from 4.2 X 10(5) to 3.5 X 10(5) M-1 for temperatures from 8 degrees to 37 degrees were calculated. The reaction is slightly exothermic (delta H = -1.2 kcal m mole-1) and strongly entropy-driven (delta S = +21 cal . mole-1 . K-1). The reaction rate constants of the warfarin-albumin interaction were determined by the stopped-flow technique. The association rate constant varies from 2.2 X 10(5) to 7.7 X 10(5) M-1 sec-1 from 10 degrees to 32 degrees. The corresponding activation enthalpy is 9.0 kcal . mole-1. These values are not consistent with a diffusion-controlled reaction. The dissociation of the complex was studied by making use of the direct competition between warfarin and phenylbutazone for the same binding site. The dissociation rate constant varies from 2.5 to 10.8 sec-1 in the same temperature range. Activation parameters obtained in the kinetic experiments correspond very well with the thermodynamic parameters calculated from the equilibrium study, validating the fluorescence approach to the equilibrium studies.

Y Engelborghs

Papers

Fluorimetric analysis of the binding of warfarin to human serum albumin. Equilibrium and kinetic study.