scholarly journals Hydration Mimicry by Membrane Ion Channels

2020 ◽  
Vol 71 (1) ◽  
pp. 461-484 ◽  
Author(s):  
Mangesh I. Chaudhari ◽  
Juan M. Vanegas ◽  
L.R. Pratt ◽  
Ajay Muralidharan ◽  
Susan B. Rempe
Keyword(s):  
Aqueous Solution ◽  
Bulk Water ◽  
Ion Binding ◽  
Ion Permeation ◽  
Free Energies ◽  
Chemical Theory ◽  
Physical Chemical ◽  
Channel Environment ◽  
Protein Channels ◽  
Specific Membrane

Ions transiting biomembranes might pass readily from water through ion-specific membrane proteins if these protein channels provide environments similar to the aqueous solution hydration environment. Indeed, bulk aqueous solution is an important reference condition for the ion permeation process. Assessment of this hydration mimicry concept depends on understanding the hydration structure and free energies of metal ions in water in order to provide a comparison for the membrane channel environment. To refine these considerations, we review local hydration structures of ions in bulk water and the molecular quasi-chemical theory that provides hydration free energies. In doing so, we note some current views of ion binding to membrane channels and suggest new physical chemical calculations and experiments that might further clarify the hydration mimicry concept.

2-Deoxyribose Radicals in the Gas Phase and Aqueous Solution. Transient Intermediates of Hydrogen Atom Abstraction from 2-Deoxyribofuranose

2005 ◽  
Vol 70 (11) ◽  
pp. 1769-1786 ◽  
Author(s):  
Luc A. Vannier ◽  
Chunxiang Yao ◽  
František Tureček
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Atom ◽  
Gas Phase ◽  
Computational Study ◽  
Hydrogen Atom Abstraction ◽  
Oh Radical ◽  
Free Energies ◽  
Intramolecular Hydrogen ◽  
Solvation Free Energies ◽  
Transient Intermediates

A computational study at correlated levels of theory is reported to address the structures and energetics of transient radicals produced by hydrogen atom abstraction from C-1, C-2, C-3, C-4, C-5, O-1, O-3, and O-5 positions in 2-deoxyribofuranose in the gas phase and in aqueous solution. In general, the carbon-centered radicals are found to be thermodynamically and kinetically more stable than the oxygen-centered ones. The most stable gas-phase radical, 2-deoxyribofuranos-5-yl (5), is produced by H-atom abstraction from C-5 and stabilized by an intramolecular hydrogen bond between the O-5 hydroxy group and O-1. The order of radical stabilities is altered in aqueous solution due to different solvation free energies. These prefer conformers that lack intramolecular hydrogen bonds and expose O-H bonds to the solvent. Carbon-centered deoxyribose radicals can undergo competitive dissociations by loss of H atoms, OH radical, or by ring cleavages that all require threshold dissociation or transition state energies >100 kJ mol-1. This points to largely non-specific dissociations of 2-deoxyribose radicals when produced by exothermic hydrogen atom abstraction from the saccharide molecule. Oxygen-centered 2-deoxyribose radicals show only marginal thermodynamic and kinetic stability and are expected to readily fragment upon formation.

A QM/MM study combined with the theory of energy representation: Solvation free energies for anti/syn acetic acids in aqueous solution

2006 ◽  
Vol 419 (1-3) ◽  
pp. 240-244 ◽  
Author(s):  
Takumi Hori ◽  
Hideaki Takahashi ◽  
Masayoshi Nakano ◽  
Tomoshige Nitta ◽  
Weitao Yang
Keyword(s):  
Aqueous Solution ◽  
Free Energies ◽  
Solvation Free Energies ◽  
Acetic Acids

Ionic effects on Supramolecular Hosts: Solvation and Counter-ion Binding in Polar Media

2021 ◽  
Author(s):  
Nicolas Moreno-Gómez ◽  
Edgar Vargas ◽  
Richard Buchner
Keyword(s):  
Aqueous Solution ◽  
Supramolecular Chemistry ◽  
Ion Binding ◽  
Host Molecules ◽  
Counter Ion ◽  
Polar Media ◽  
Counter Ion Binding ◽  
Ionic Effects

For the progress of synthetic supramolecular chemistry in aqueous solution the design of host molecules soluble in this medium is essential. A possible route is the introduction of ionic residues,...

scholarly journals Metal Ion-Binding Properties of the Diphosphate Ester Analogue, Methylphosphonylphosphate, in Aqueous Solution

1999 ◽  
Vol 6 (6) ◽  
pp. 321-328 ◽  
Author(s):  
Bin Song ◽  
Jing Zhao ◽  
Fridrich Gregáň ◽  
Nadja Prónayová ◽  
S. Ali A. Sajadi ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Metal Ion ◽  
Minor Role ◽  
Ion Binding ◽  
Metal Ion Binding ◽  
Ph Titration ◽  
Role Based ◽  
The Stability ◽  
A Minor ◽  
Complex Stabilities

The stability constants of the 1:1 complexes formed between methylphosphonylphosphate (MePP3-), CH3P(O)2--O-PO32- , and Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+,​ or Cd2+ (M2+) were determined by potentiometric pH titration in aqueous solution (25 C° ; l = 0.1 M, NaNO3 ). Monoprotonated M(H;MePP) complexes play only a minor role. Based on previously established correlations for M2+ -diphosphate monoester complex-stabilities and diphosphate monoester β-group. basicities, it is shown that the M(Mepp)- complexes for Mg2+ and the ions of the second half of the 3d series, including Zn2+ and Cd2+, are on average by about 0.15 log unit more stable than is expected based on the basicity of the terminal phosphate group in MePP3-. In contrast, Ba(Mepp)- and Sr(Mepp)- are slightly less stable, whereas the stability for Ca(Mepp)- is as expected, based on the mentioned correlation. The indicated increased stabilities are explained by an increased basicity of the phosphonyl group compared to that of a phosphoryl one. For the complexes of the alkaline earth ions, especially for Ba2+, it is suggested that outersphere complexation occurs to some extent. However, overall the M(Mepp)- complexes behave rather as expected for a diphosphate monoester ligand.

The three types of liquid water in the surface of present Mars

2009 ◽  
Vol 9 (1) ◽  
pp. 45-49 ◽  
Author(s):  
D. Möhlmann
Keyword(s):  
Solid State ◽  
Liquid Water ◽  
Bulk Water ◽  
Pure Liquid ◽  
Interfacial Water ◽  
Biological Processes ◽  
Undercooled Liquid ◽  
Liquid Bulk ◽  
Physical Chemical

AbstractThermodynamics teaches that pure liquid bulk water cannot stably exist on the surface of Mars. However, it is shown by thermodynamic arguments that liquid water can exist, at least temporarily, in the upper surface of Mars, in form of: (a) undercooled liquid interfacial water (ULI water); (b) undercooled liquid water in cryo-brines; and (c) liquid bulk water (due to solid-state greenhouse subsurface melting) in the subsurface of ice areas, which are covered by a lid of solid ice only. The presence of these forms of liquid water on present Mars is discussed in detail and in view of the possible consequences for physical, chemical and eventual biological processes.

General parameterized SCF model for free energies of solvation in aqueous solution

1991 ◽  
Vol 113 (22) ◽  
pp. 8305-8311 ◽  
Author(s):  
Christopher J. Cramer ◽  
Donald G. Truhlar
Keyword(s):  
Aqueous Solution ◽  
Free Energies
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