Hydration coupling parameter

Jorgensen, Blake, and Buckner " reported a staged FEP calculation of the hydration free energy of methane, which was treated as a Lennard-Jones (LJ) sphere. The size (a) and well depth (e) LJ parameters were each scaled linearly with the coupling parameter lambda ... 

As discussed in the methods section, computational techniques used to study hydrophobic interactions are similar to those used for hydrophobic hydration. Most commonly, TI and FEP methods have been adapted to yield a PMF by equating the coupling parameter A, or the perturbation coordinate, respectively, to the radial distance between two solute particles. The application of a test particle approach or of Eq. [28] is also possible. Methods for decomposition of the free energy of association into its entropic and energetic (enthalpic) parts are equivalent to those discussed above, as are techniques for determining the heat capacity. 

The employment of NMR-active isotopes permits to access experimental parameters which are intrinsically difficult to measure, unless a significant concentration of the sugar is present in the NMR tube. For instance, aqueous solutions of N-acetyIncuraminic acid, labeled with 13C at Cl, C2, and/or C3, were analyzed to detect and quantify the various chemical species present in equilibrium at different pHs. In fact, in addition to the expected a and (3 pyranose forms, acyclic keto, keto hydrate and enol forms were identified on the basis of 13C NMR spectroscopic data. Besides, DFT methods were employed to predict the effect of enol and hydrate structure on the coupling constant values Jc,u and /c c involving C2 and C3, finding that 2/c2,h3 can be safely used to differentiate the cis and tram isomers of the enol forms.9... 

The most important NMR parameters obtained for the hydroxyl protons are chemical shifts (6), vicinal proton-proton coupling constants (3J7hc,Oh), temperature coefficients (AS/7), deuterium-induced differential isotope shifts, and exchange rates ( ex)-119-123 These parameters may provide information on hydrogen bond interactions and hydration as well. Moreover NOEs and chemical exchanges involving hydroxyl groups observed by NOESY and ROESY experiments also add to the number of distance restraints used in conformational analysis. 

In many respect the fifteen acinides [Ac(Z = 89) to Fm(Z = 103)] with their 5/ configurations, are similar to their lanthanide counterpart. Thus the chemical properties like the extraction behaviour, complex formation and the spectroscopic properties often show close parallelism with those of the lanthanides. The Lande parameter, f5y, is some two to two and half times larger in the 5/series than in the corresponding 4/ series. As a result of this, the deviation from the Russell-Sauders coupling in the 5/ series is much more pronounced than in the 4/series. However, it has been shown earlier by Sinha 58) that the hydration entropies, enthalpies and the crystal parameters for the fluorides of the tri- and tetravalent actinides (Fig. 55, 56) also follow a linear L-dependence and give rise to the inclined W plots like those for the lanthanides. 

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