Effect of acetonitrile on the hydration of human serum albumin films: A calorimetric and spectroscopic study

A new experimental approach based on the combination of calorimetric and FTIR spectroscopic measurements was proposed to study simultaneously the sorption of water and organic solvent, and corresponding changes in the structure of protein films in the water activity range from 0 to 1.0. Enthalpy changes (ΔHtot) on the interaction of water with the dried human serum albumin (HSA) in the presence and absence of acetonitrile (AN) have been measured using a Setaram BT-2.15 calorimeter at 298 K. Spectroscopic data on water and organic solvent vapor sorption by the HSA films and the corresponding changes in the protein secondary structure were determined by means of a Bruker Vector-22 FTIR spectrometer. By using a water activity-based comparison we characterised the effect of acetonitrile on the hydration and structure of the HSA films. Acetonitrile (AN) sorption isotherm resembles a smooth curve. HSA film binds about 250 mol AN/mol protein at the lowest water activities. As the water activity increases from 0 to 0.8, the sorption of AN gradually decreases from 250 to 150 mol AN/mol HSA. At aw > 0.8, the sorption of AN sharply decreases to zero. Acetonitrile decreases markedly the water content at a given aw. This behavior suggests that the suppression in the uptake of water is due to a competition for water-binding sites on the HSA films by acetonitrile. Changes in the secondary structure of HSA were determined from infrared spectra by analyzing the structure of amide I band. Acetonitrile increases the intensity of the 1654 cm-1 band that was assigned to the α-helix structure. Changes in the intensity of the 1654 cm-1 band agree well with the decrease in water uptake in the presence of AN. An explanation of the acetonitrile effect on the hydration and structure of the HSA films was provided on the basis of hypothesis on water-assisted disruption of polar contacts in the initially dried protein. © 2004 Elsevier B.V. All rights reserved

Heat effects of dehydration of human serum albumin in organic solvents

Based on analysis of our own results concerning the thermochemistry of the interactions of serum albumin in organic media with a low water content and the adsorption of water on the protein in conjunction with the published data on the thermochemistry of solvation of water in organic solvents, we suggest a scheme capable of predicting the influence of the solvation ability of the medium on the enthalpies of dehydration of the protein in organic solvents. Copyright © 2005 by Pleiades Publishing, Inc

Effect of dioxane on the hydration of human serum albumin as studied by isothermal calorimetry and IR spectroscopy

A comparison of isothermal calorimetry data on the interaction of human serum albumin with water in the presence and absence of dioxane and of the isotherms of adsorption of vapors of water and dioxane on HSA as measured by IR spectroscopy made it possible to suggest an experimental method for isolating the contribution from the organic solvent to the thermodynamic and sorption characteristics of hydration of the protein over the entire range of water activities. © Pleiades Publishing, Inc., 2006

The influence of dioxane on the hydration of bovine pancreatic α-chymotrypsin according to isothermal calorimetry and IR spectroscopy data

The influence of dioxane on the thermochemical characteristics of the hydration of bovine pancreatic α-chymotrypsin enzyme over the whole range of water thermodynamic activities was studied by comparing the isothermal calorimetry data on the thermochemistry of interaction between the enzyme and water in the presence and absence of dioxane and using the IR spectral data on the adsorption of water and organic solvent vapors on the protein. © Nauka/Interperiodica 2006

Guided random walk calculation of energies and <\sq {r^2} > values of the 1Σg^1\Sigma_g state of H_2 in a magnetic field

Energies and spatial observables for the $^1\Sigma_g$ state of the hydrogen molecule in magnetic fields parallel to the proton-proton axis are calculated with a guided random walk Feynman-Kac algorithm. We demonstrate that the accuracy of the results and the simplicity of the method may prove it a viable alternative to large basis set expansions for small molecules in applied fields.Comment: 10 pages, no figure

Recovery of the electric strength in a cold cathode thyratron

The paper deals with the investigations of the recovery process of electric strength in a cold cathode thyratron. Method which allows extracting the plasma of the preceding discharge not only from the cathode cavity but also from the main gap of the thyratron is proposed. Method is based on the usage of a low-current nonsteady state discharge in the pause between the pulses

Hydration-dehydration of human serum albumin studied by isothermal calorimetry and IR spectroscopy

Based on a comparison of the data on the isothermal calorimetry of the interaction of human serum albumin with water and the adsorption isotherms of water vapor on the protein obtained by IR spectroscopy, an experimental method was used for the first time to study the thermochemical and sorption characteristics of protein hydration-dehydration over the entire range of the thermodynamic activities of water. A mechanism was proposed to explain the relationships between the thermochemical properties, protein water content, and the moistening method. © 2007 Pleiades Publishing, Ltd

Photon Filamentation in Resonant Media with High Fresnel Numbers

The phenomenon of turbulent photon filamentation occurs in lasers and other active optical media at high Fresnel numbers. A description of this phenomenon is suggested. The solutions to evolution equations are presented in the form of a bunch of filaments chaotically distributed in space and having different radii. The probability distribution of patterns is defined characterizing the probabilistic weight of different filaments. The most probable filament radius and filament number are found, being in good agreement with experiment.Comment: Revtex file, 5 pages. Reference to the English edition of the journal is give