K. R. Grigoryan

Fluorescent Analysis of the Structural Changes of Human Serum Albumin Induced by Low Temperatures in Water-Dimethyl Sulfoxide Solutions

Structural changes in human serum albumin (HSA) induced by low temperatures in water-dimethyl sulfoxide (DMSO) solutions were studied by fluorescent spectroscopy. The emission, synchronous, and isopotential synchronous spectra (3D spectra) of the HSA were analyzed. It was shown that protein does not undergo drastic structural changes in the fast freezing/defrosting mode in solutions of up to 20% DMSO but becomes more compact.

Preferential solvatation of human serum albumin in dimethylsulfoxide-H2O binary solution

The preferential solvatation of human serum albumin (HSA) in dimethylsulfoxide (DMSO) aqueous solutions were studied using the densitometry method. It has been shown that at DMSO low concentrations HSA undergoes to preferential hydration, but at DMSO higher concentrations preferential binding of DMSO molecules to protein occurs. It has been estimated that DMSO exhibits stabilizing/destabilizing effect on HSA structure which is explained in terms of hydration/solvatation of protein, on the one hand, and the medium structure enhancement/disruption around the protein molecule, on the other hand.

The effect of solvated ions on the thermal denaturation of human serum albumin in water-dimethylsulfoxide solutions

The effects of solvated ions on the thermal denaturation of human serum albumin (HAS) in water-dimethylsulfoxide (DMSO) solutions were studied by the method of electron absorption spectroscopy. It was shown that depending on the DMSO concentration, electrolytes (LiCl, LiNO3, LiClO4, NaCl, and NaNO3) contained in these solutions were characterized by different anion and cation solvation degrees: unlike cations, anions were only negligibly solvated, which affected HAS thermal denaturation. Electrostatic interactions between anions and positively charged amino acid residues supporting protein denaturation subsided in the line Cl− > NO3− > ClO4−.

Intermolecular interactions in albumin-sulfoxide-water systems at low temperatures, investigated by means of fluorescence quenching

The effect of low temperatures on the interaction in human serum albumin (HSA)-diethyl sulfoxife (DESO)-dipropyl sulfoxide (DPSO)-water systems is investigated by means of fluorescence spectroscopy (intrinsic protein fluorescence, three-dimensional excitation/emission matrix (3D EEM)). The Stern-Volmer constants of HSA quenching are calculated for these systems. The structural changes occurring in these systems are characterized using 3D EEM profiles of HSA. It is shown that the HSA structural changes depend not only on the direct interaction of protein with sulfoxides but on structural changes in the solvent as well.

Analysis of the interaction of gallic acid and myoglobin by UV-vis absorption spectroscopy

UV-vis absorption spectroscopy has been used to analyze the interaction of myoglobin (Мb) and gallic acid (GA). The binding constants (4.38 × 104 M–1 at 298.15 K and 0.42 × 104 М–1 at 308.15K), the number of binding sites (h = 1.0), and the thermodynamic parameters of binding (ΔH, ΔS, and ΔG) have been determined. Hydrogen bonds have been shown to play a major role in the stabilization of the GA–Мb complexes. GA binding led to slight changes in the electronic state of the heme ring of the protein.

Intermolecular interactions in aqueous solutions of gallic acid at 296–306 K according to spectrofluorimetry and densimetry data

Features of intermolecular interactions in aqueous solutions of gallic acid (GA) are studied by means of densimetry and fluorescence spectroscopy (intrinsic fluorescence, 2D spectra, and excitation/ emission matrix fluorescence spectra, 3D) at 296.15, 301.15, and 306.15 K in the concentration range of 5.88 × 10−4–5.88 × 10−2 mol L−1. It is shown by analyzing the concentration and temperature dependences of the apparent molar volumes and fluorescence parameters of GA that the equilibrium between nonassociated and associated species in the solution and the hydration of these species undergo changes.

Experimental and theoretical studies on the solvation of potassium and chlorine ions in aqueous dimethylsulfoxide solutions

Based on experimental (viscosimetric) studies, the physicochemical characteristics of solvated potassium and chlorine ions in dimethylsulfoxide-containing (DMSO) aqueous solutions are determined in the temperature range 25-40 °C. The Hartree–Fock nonempirical method (ab initio) with the (6-31+G(d,p)) basis set is used to calculate the structural and energy parameters of (K+,Cl–)/H2O and (K+,Cl–)/ /(H2O+DMSO) complexes in vacuum; the solvent effect is taken into account by the self-consistent reaction field (SCRF) method within the Onsager model. It is found that the solvation of individual ions in water–DMSO mixtures is due to the properties and structural features of the mixed solvent and the nature of the ions.

Physicochemical Peculiarities of Iodine-Dimethylsulfoxide-H2O Solutions and Effect on Ion Binding to Bovine Serum Albumin

The interaction of iodine with bovine serum albumin (BSA) in dimethylsulfoxide (DMSO) aqueous solutions was studied by means of fluorescence and UV/Vis absorption spectroscopy methods. Physicochemical peculiarities of these solutions were revealed. The results showed that the tri-iodide ion formed in the 1DMSO : 2H2O solution caused the fluorescence quenching of BSA. The modified Stern-Volmer quenching constant and corresponding thermodynamic parameters, the free energy change (), enthalpy change (), and entropy change (), at different temperatures (293, 298, and 303 K) were calculated, which indicated that the hydrophobic and electrostatic interactions were the predominant operating forces. The binding locality distance r between BSA and tri-iodide ion at different temperatures was determined based on Forster nonradiation fluorescence energy transfer theory.