Ionic binding of human serum albumin — dependence on pH and ionic strength: a chromatographic approach

Analysis of the progesterone displacement of its human serum albumin binding site by beta-estradiol using biochromatographic approaches: effect of two salt modifiers

The mechanisms of (i) the binding of two sex-hormones (i.e. progesterone and beta-estradiol) to human serum albumin (HSA) and (ii) the progesterone displacement of its HSA binding cavity by beta-estradiol were studied by biochromatography using three different methods. In the first time, zonal elution method was used to prove the direct competition effect between the two sex-hormone. In the second time, the competition effect between beta-estradiol and progesterone to bound on the same HSA site was analysed by the competitive bi-Langmuir approach. Finally, the thermodynamic data of these two binding processes were studied. The Gibbs free energy value (Delta(approximately)G degrees) of the displacement equilibrium was negative demonstrating that beta-estradiol displaced progesterone of its HSA binding cavity. Moreover, the effect of two chloride modifiers (i.e. Na(+), Mg(2+)) on these two binding processes were analysed. Results showed that in the salt biological concentration ranges, the Mg(2+) cation enhanced strongly the bioavailable progesterone, whereas the Na(+) cation interacted slowly on the progesterone displacement of its HSA binding site by beta-estradiol. This study showed that it must be useful to carry out more in vivo test on the magnesium supplementation effect for women who suffer from estrogen dominance syndrome.

Anti-coagulant rodenticide binding properties of human serum albumin: a biochromatographic approach

In this paper, the anti-coagulant rodenticide-human serum albumin (HSA) binding was investigated using a perturbation method to calculate the solute distribution isotherms. It was shown that rodenticide can bound either on the benzodiazepine HSA site with low affinity (site I) or on the warfarin HSA site with high affinity (site II). The thermodynamic parameters of this association were calculated for the two HSA binding sites. For the site II, the rodenticide-HSA association was governed enthalpically whereas for the site I, this one was driven entropically. Moreover, the role of the magnesium (Mg(2+)) and calcium (Ca(2+)) on this association was carried out. It was clearly demonstrated that the rodenticide affinity for the site I was not affected by modifying the bulk solvent surface tension whereas for the site II the association constant increased strongly with the Mg(2+) or the Ca(2+) concentration in the bulk solvent. These results showed that the rodenticide-HSA affinity and thus the rodenticide toxicological effect depends on the Mg(2+) or Ca(2+) concentration.

Testimony of the correlation between DHEA and bioavailable testosterone using a biochromatographic concept: effect of two salts

In a previous paper (C. André et al., submitted to J. Chromatogr. B) a mathematical model based on the Langmuir theory was developed to visualize the competition effect between testosterone and deshydroepiandrosterone (DHEA) for their identical human serum albumin (HSA) binding cavity. In this work, the thermodynamic mechanisms of (i) the binding of two hormones, DHEA and testosterone to HSA and (ii) the testosterone displacement of its HSA binding cavity by DHEA was studied by biochromatography. The Na+ cation effect used as physico-chemical marker of these binding processes was clearly described. The Gibbs free energy value (DeltaGo ) of the displacement equilibrium was always negative demonstrating that DHEA well displaced testosterone of its HSA binding cavity. The thermodynamic data also showed that this displacement equilibrium was enthalpically controlled. Moreover, the effect of (Mg2+) concentration (x') on the two binding mechanisms was analyzed. It appeared that for old men with a deficit of testosterone, Mg(2+) supplementation during treatment with DHEA can increased the free testosterone concentration and its biological effect. All these results must be confirmed by in vivo test.

Phloroglucinol: novel synthesis and role of the magnesium cation on its binding with human serum albumin (HSA) using a biochromatographic approach based on Langmuir isotherms

In this paper, a new and efficient method for synthesis of phloroglucinol with an overall yield of 60% was described. As well, the phloroglucinol association on an immobilized human serum albumin (HSA) column was analyzed in biochromatography by the determination of its Langmuir distribution isotherms. The role of the magnesium cation Mg2+ on the phloroglucinol-HSA binding process was as well analyzed. The results showed that in the Mg2+ concentration range (0.7-2 mM) (including its biological concentration range, i.e. 0.75-0.90 mM), increasing the Mg2+ concentration increased the fraction of free phloroglucinol (not linked with HSA) and thus its biological effect.

Role of the magnesium cation on antihypertensive molecule-human serum albumin binding: affinity chromatography approach

The role of the Mg2+ cation on antihypertensive molecule binding on human serum albumin (HSA) was studied by affinity chromatography. The thermodynamic data corresponding to this binding were determined for a wide range of Mg2+ concentrations (c). For the nifedipine molecule, an increase in the Mg2+ concentration produced a decrease in binding due to a decrease in the electrostatic interactions. For verapamil and diltiazem, which have the highest solvent accessible surface area, the solute binding on HSA was divided into two Mg2+ concentration regions. For a low c value below c(c) (approximately 1.6 mmol/l), the binding dependence with c was similar to that of nifedipine. For c above c(c) the hydrophobic effect created in the bulk solvent associated with a decrease in the van der Waals interactions between the solute molecule and the HSA implied a decrease in its binding. These results showed that for patients with hypertension, an Mg2+ supplementation during treatment with these antihypertensive molecules can increase the active pharmacological molecule concentration.