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

Interaction enthalpies of solid bovine pancreatic α-chymotrypsin with organic solvents: Comparison with FTIR- spectroscopic data

Calorimetric heat effects and integral absorbance changes observed in the FTIR spectra were measured at immersing solid bovine pancreatic α-chymotrypsin in organic solvents and water at 298 K. Enthalpy changes upon the immersion of the enzyme in different media are in a good linear correlation with the corresponding IR-absorbance changes. Based on calorimetric and FTIR data, all the solvents were divided into two groups. The first group of solvents includes carbon tetrachloride, benzene, nitromethane, acetonitrile, 1,4-dioxane, n-butanol, n-propanol and pyridine in which no significant heat evolution and structural changes were found at the solid enzyme immersion. Second group of the solvents includes dimethyl sulfoxide, methanol, ethanol, and water. Immersion into these media, results in the solid protein swelling and involves significant exothermic heat evolution and structural changes in the protein. Dividing of different media in these two groups is in a qualitative correlation with the solvent hydrophilicity which is defined as partial excess molar Gibbs free energy of water at infinite dilution in a given solvent. The first group of solvents includes liquids with hydrophilicity exceeding 2.7 kJ/mol. The hydrophilicity of the second group solvents is <2.3 kJ/mol. Hydrogen bond donating ability of the solvents assists in the protein swelling. Hydrogen bonding between protein and solvent is assumed to be a main factor controlling the swelling of solid protein preparation in the solvents at room temperature. © 2002 Elsevier Science B.V. All rights reserved

Calorimetric and FTIR-spectroscopic study of solvent effect on the state of dry solid bovine pancreatic α-chymotrypsin immersed in anhydrous organic solvents

Calorimetric heat effects and structural rearrangements accompanying the immersion of dry solid bovine pancreatic α-chymotrypsin in anhydrous organic solvents and water were measured at 298 K. It was found that the enthalpy and IR-absorbance changes being put together obey good linear correlation. According to the extent of their influence on the protein structure and thermodynamic state the solvents could be divided into two groups. The first group exhibiting nearly zero effects consists of carbon tetrachloride, benzene, nitromethane, acetonitrile, 1, 4-dioxane, n-butanol, n-propanol and pyridine. Dry solid protein is suggested to be stable in such media due to kinetic reasons. Immersion of the protein into a second group solvents, namely, dimethyl sulfoxide, methanol, ethanol, and in pure water as well, is followed by swelling of the protein and accompanied with significant exothermic enthalpy change and structural rearrangements. It was shown that attribution of the solvent to the first or the second group is determined by its thermody-namic hydrophilicity (partial excess molar Gibbs free energy of water in a given solvent at infinite dilution). The first group consists of liquids with thermodynamic hydrophilicities all above 2.7 kJ/mol. The thermodynamic hydrophilicities of the second group solvents are lower than 2.3 kJ/mol. At close hydrophilicities the presence of mobile protons in the solvent molecule sufficiently accelerates the solid protein swelling. It is deduced that thermodynamic hydrophilicity and proton donating ability could be principal factors controlling the stability of dry solid proteins and kinetics of swelling in liquids examined at room temperature

Calorimetric and Fourier transform infrared spectroscopic study of solid proteins immersed in low water organic solvents

Calorimetric heat effects and structural rearrangements assessed by means of Fourier transform infrared (FTIR) amide I spectra were followed by immersing dry human serum albumin and bovine pancreatic α-chymotrypsin in low water organic solvents and in pure water at 298 K. Enthalpy changes upon immersion of the proteins in different media are in a good linear correlation with the corresponding IR absorbance changes. Based on calorimetric and FTIR data the solvents were divided into two groups. The first group includes carbon tetrachloride, benzene, nitromethane, acetonitrile, 1,4-dioxane, n-butanol, n-propanol and pyridine where no significant heat evolution and structural changes were found during protein immersion. Due to kinetic reasons no significant protein-solvent interactions are expected in such systems. The second group of solvents includes dimethyl sulfoxide, methanol, ethanol, and water. Immersion of proteins in these media results in protein swelling and involves significant exothermic heat evolution and structural changes in the protein. Dividing of different media in the two groups is in a qualitative correlation with the solvent hydrophilicity defined as partial excess molar Gibbs free energy of water at infinite dilution in a given solvent. The first group includes the solvents with hydrophilicity exceeding 2.7 kJ/mol. More hydrophilic second group solvents have this energy values less than 2.3 kJ/mol. The hydrogen bond donating ability of the solvents also assists in protein swelling. Hydrogen bonding between protein and solvent is assumed to be a main factor controlling the swelling of dry solid proteins in the studied solvents. © 2001 Elsevier Science B.V

Rational modes of work and rest of staff

Для поддержания высокой работоспособности и предупреждения утомления в процессе работы большое значение имеет рациональная организация труда и отдыха.To maintain high efficiency and prevent fatigue in the process, great importance is the rational organization of work and rest

Maternal capital and the ways of their solution

В данной статье раскрыты положительные и отрицательные стороны материнского капитала.This article reveals positive and negative aspects of the parent capital and presented a clear picture of the increase in demand for housing by the use of the parent capital

The development of shared construction, using programs of Sberbank of Russia

В данной статье говорится о долевом строительстве, о его преимуществах и недостатках, рассматривается программа Сбербанка «Строящееся жилье» и приводятся результаты этой программы.This article refers to the joint construction, its advantages and disadvantages, discusses the program of Sberbank "housing under Construction"

Maternal capital and the ways of their solution

В данной статье раскрыты положительные и отрицательные стороны материнского капитала.This article reveals positive and negative aspects of the parent capital and presented a clear picture of the increase in demand for housing by the use of the parent capital

Level density and thermal properties in rare earth nuclei

A convergent method to extract the nuclear level density and the gamma-ray strength function from primary gamma-ray spectra has been established. Thermodynamical quantities have been obtained within the microcanonical and canonical ensemble theory. Structures in the caloric curve and in the heat capacity curve are interpreted as fingerprints of breaking of Cooper pairs and quenching of pairing correlations. The strength function can be described using models and common parameterizations for the E1, M1 and pygmy resonance strength. However, a significant decrease of the pygmy resonance strength at finite temperatures has been observed.Comment: 15 pages including 8 figures. Proceedings article for the conference Nuclear Structure and Related Topics, Dubna, Russia, June 6-10, 200

A precision study of two eclipsing white dwarf plus M dwarf binaries

We use a combination of X-shooter spectroscopy, ULTRACAM high-speed photometry and SOFI near-infrared photometry to measure the masses and radii of both components of the eclipsing post common envelope binaries SDSS J1212-0123 and GK Vir. For both systems we measure the gravitational redshift of the white dwarf and combine it with light curve model fits to determine the inclinations, masses and radii. For SDSS J1212-0123 we find a white dwarf mass and radius of 0.439 +/- 0.002 Msun and 0.0168 +/- 0.0003 Rsun, and a secondary star mass and radius of 0.273 +/- 0.002 Msun and 0.306 +/- 0.007 Rsun. For GK Vir we find a white dwarf mass and radius of 0.564 +/- 0.014 Msun and 0.0170 +/- 0.0004 Rsun, and a secondary star mass and radius of 0.116 +/- 0.003 Msun and 0.155 +/- 0.003 Rsun. The mass and radius of the white dwarf in GK Vir are consistent with evolutionary models for a 50,000K carbon-oxygen core white dwarf. Although the mass and radius of the white dwarf in SDSS J1212-0123 are consistent with carbon-oxygen core models, evolutionary models imply that a white dwarf with such a low mass and in a short period binary must have a helium core. The mass and radius measurements are consistent with helium core models but only if the white dwarf has a very thin hydrogen envelope, which has not been predicted by evolutionary models. The mass and radius of the secondary star in GK Vir are consistent with evolutionary models after correcting for the effects of irradiation by the white dwarf. The secondary star in SDSS J1212-0123 has a radius ~9 per cent larger than predicted.Comment: 21 pages, 14 Figures and 11 Tables. Accepted for publication in MNRA