Calculation of Equilibrium Constant for Dimerization of Heavy Water Molecules in Saturated Vapor

2015 ◽  
Vol 60 (3) ◽  
pp. 263-267
Author(s):  
L.A. Bulavin ◽  
◽  
S.V. Khrapatyi ◽  
V.M. Makhlaichuk ◽  
Keyword(s):  
Equilibrium Constant ◽  
Heavy Water ◽  
Saturated Vapor ◽  
Water Molecules

The Densities of Heavy Water Liquid and Saturated Vapor at Elevated Temperatures

1958 ◽  
Vol 62 (4) ◽  
pp. 431-433 ◽  
Author(s):  
G. M. Hebert ◽  
H. F. McDuffie ◽  
C. H. Secoy
Keyword(s):  
Heavy Water ◽  
Elevated Temperatures ◽  
Saturated Vapor

Water dimer equilibrium constant of saturated vapor

2014 ◽  
Vol 88 (8) ◽  
pp. 1287-1292 ◽  
Author(s):  
N. P. Malomuzh ◽  
V. N. Mahlaichuk ◽  
S. V. Khrapatyi
Keyword(s):  
Equilibrium Constant ◽  
Saturated Vapor ◽  
Water Dimer

The Hydration of Ketones in Mixtures of Water and Polar Aprotic Solvents

1972 ◽  
Vol 50 (13) ◽  
pp. 1992-1999 ◽  
Author(s):  
Ross Stewart ◽  
John D. Van Dyke
Keyword(s):  
Activity Coefficient ◽  
Water Content ◽  
Equilibrium Constant ◽  
Carbonyl Group ◽  
Pure Water ◽  
Solvent Composition ◽  
Water Molecules ◽  
Aprotic Solvents ◽  
Acid Catalyzed

The hydration of a series of ring-substituted trifluoroacetophenones (Z) has been studied by means of u.v. and n.m.r. spectroscopy in DMSO–water and sulfolane–water mixtures. The W0 function is defined as [Formula: see text] where Kd is the equilibrium constant for the reaction [Formula: see text]Mixtures of water and sulfolane in all proportions have a dehydrating effect compared to water but mixtures of water and DMSO down to 15 mol % water are more hydrating with respect to the carbonyl group of trifluoroacetophenones than is pure water. An analysis of activity coefficient behavior indicates that the diol, ZH2O, has a higher requirement for solvation by water molecules than does water itself.The rate of the uncatalyzed hydration in aqueous sulfolane drops drastically as the water content of the medium decreases, whereas the rate of the acid-catalyzed reaction is not greatly affected by changes in the solvent composition; a plot of log k for both catalyzed and uncatalyzed reactions is approximately linear in W0.

scholarly journals Theoretical Investigation into the Change in the Number of Water Molecules in Solvent Inaccessible Region of an Enzyme and Enzyme-substrate Complex

2019 ◽  
pp. 1-17
Author(s):  
Ikechukwu Iloh Udema ◽  
Abraham Olalere Onigbinde
Keyword(s):  
Free Energy ◽  
Equilibrium Constant ◽  
Preferential Solvation ◽  
Energy Difference ◽  
Theoretical Research ◽  
Water Molecules ◽  
Free Energy Difference ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
Theoretical Issues

Background: There may be dry enzymes, but water remains indispensable for the catalytic action of enzymes. There is not as much interest in how the presence of a drug such as aspirin and a psychoactive compound such as ethanol may affect the water-mediated role of the enzyme. Objectives: The objectives of this research are: 1) To assess the changes in the number of water molecules interacting with the enzyme-substrate complex and the solvent inaccessible region of a protein, 2) to determine the free energy difference due to preferential solvation and hydration, and 3) to re-examine theoretical issues in literature and relate them to the interpretation of the results. Methods: A major theoretical research and minor experimentation using Bernfeld method. Results and Discussion: The presence of ethanol/aspirin alone yielded only dehydration of the osmolyte inaccessible region and the enzyme substrate complex (ES). There was positive free energy difference (DDG) if the equilibrium constant for hydration change (Keq(1))> the equilibrium constant for folding-unfolding transition (Keq(3)); it is negative where Keq(3)> Keq(1). Analysis of various models made them valuable for the interpretation of result for feature application. Conclusion: The change in the number of water molecules in an osmolyte inaccessible region of the enzyme and those interacting with the ES may be either positive or negative due respectively to sucrose and ethanol/aspirin. The spontaneity of two processes, hydration and folding-unfolding transition, the free energy difference, differs. The model for water stripping, preferential interaction concept, and the KBI for osmolation and hydration can guide the interpretation of the effects of any cosolute.

scholarly journals Shaker-IR K+ channel gating in heavy water: Role of structural water molecules in inactivation

2021 ◽  
Vol 153 (6) ◽  
Author(s):  
Tibor G. Szanto ◽  
Szabolcs Gaal ◽  
Izhar Karbat ◽  
Zoltan Varga ◽  
Eitan Reuveny ◽  
...  
Keyword(s):  
Heavy Water ◽  
Conformational Stability ◽  
External Solution ◽  
Md Simulations ◽  
Selectivity Filter ◽  
K Channel ◽  
Inactivation Kinetics ◽  
Water Molecules ◽  
Structural Water ◽  
Wide Range

It has been reported earlier that the slow (C-type) inactivated conformation in Kv channels is stabilized by a multipoint hydrogen-bond network behind the selectivity filter. Furthermore, MD simulations revealed that structural water molecules are also involved in the formation of this network locking the selectivity filter in its inactive conformation. We found that the application of an extracellular, but not intracellular, solution based on heavy water (D2O) dramatically slowed entry into the slow inactivated state in Shaker-IR mutants (T449A, T449A/I470A, and T449K/I470C, displaying a wide range of inactivation kinetics), consistent with the proposed effect of the dynamics of structural water molecules on the conformational stability of the selectivity filter. Alternative hypotheses capable of explaining the observed effects of D2O were examined. Increased viscosity of the external solution mimicked by the addition of glycerol had a negligible effect on the rate of inactivation. In addition, the inactivation time constants of K+ currents in the outward and the inward directions in asymmetric solutions were not affected by a H2O/D2O exchange, negating an indirect effect of D2O on the rate of K+ rehydration. The elimination of the nonspecific effects of D2O on our macroscopic current measurements supports the hypothesis that the rate of structural water exchange at the region behind the selectivity filter determines the rate of slow inactivation, as proposed by molecular modeling.

scholarly journals Validation of Thermal Neutron Scattering Cross Sections for Heavy Water based on Molecular Dynamics Simulation

2019 ◽  
Vol 211 ◽  
pp. 06001
Author(s):  
Haelee Hyun ◽  
Do Heon Kim ◽  
Young-Ouk Lee
Keyword(s):  
Molecular Dynamics ◽  
Frequency Spectrum ◽  
Heavy Water ◽  
Cross Sections ◽  
Dynamics Simulation ◽  
Water Model ◽  
Water Molecules ◽  
Scattering Cross ◽  
Thermal Scattering ◽  
Scattering Cross Sections

Recently, the thermal scattering libraries of ENDF/B-VIII.0 and JEFF-3.3 for light and heavy water were released with a new water model (CAB model) proposed by Damian. For the CAB model, the molecular dynamics code GROMACS was used to more accurately describe the realistic motions of water molecules. In this paper, to consider the coherent component we also generated the thermal scattering cross section of the deuterium and oxygen bound in the heavy water molecules using the GROMACS code and EPSR code. In addition, the frequency spectrum was also calculated using the GROMACS code. Thermal scattering cross sections based on the newly calculated Sköld correction factor and the frequency spectrum were generated by NJOY2016 code. Finally, the performance of the generated thermal scattering cross sections were validated by performing an ICSBEP benchmark simulation using MCNPX code.

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