Molecular water probe model

Cruciani et al., used a dynamic physicochemical interaction model to evaluate the interaction energies between a water probe and the hydrophilic and hydrophobic regions of the solute with the GRID force field. The VolSurf program was used to generate a PLS model able to predict log Poet [51] from the 3D molecular structure. 

Macroscopic experiments allow determination of the capacitances, potentials, and binding constants by fitting titration data to a particular model of the surface complexation reaction [105,106,110-121] however, this approach does not allow direct microscopic determination of the inter-layer spacing or the dielectric constant in the inter-layer region. While discrimination between inner-sphere and outer-sphere sorption complexes may be presumed from macroscopic experiments [122,123], direct determination of the structure and nature of surface complexes and the structure of the diffuse layer is not possible by these methods alone [40,124]. Nor is it clear that ideas from the chemistry of isolated species in solution (e.g., outer-vs. inner-sphere complexes) are directly transferable to the surface layer or if additional short- to mid-range structural ordering is important. Instead, in situ (in the presence of bulk water) molecular-scale probes such as X-ray absorption fine structure spectroscopy (XAFS) and X-ray standing wave (XSW) methods are needed to provide this information (see Section 3.4). To date, however, there have been very few molecular-scale experimental studies of the EDL at the metal oxide-aqueous solution interface (see, e.g., [125,126]). 

Similar to the theoretical model of Palm et al. [54], based on dynamic surface properties for the prediction of drug absorption into human intestinal Caco-2 cell lines the authors used their molecular dynamics/GRID approach to correlate the absorption of the same set of six P-adrenoceptor antagonists with the coefficients obtained by the water probe at contour level -2 and -3 kcal/mol. 

One may now extend such detailed study of the molecular/water interfaces to shed light on processes more directly relevant to corrosion. For instance, specific details regarding the reactivity of water molecules at the metal-water interface have been modeled with varying degrees of sophistication [27, 28, 112-116]. The dissociation of H2O at the surface into products presents an important first probe reaction and bas been related to the initiation of passivity of fresh metal surfaces when first exposed to aqueous solution ... 

In other words, the tautomerism of histidines constitutes a molecular environmental probe. Moreover, model studies for the interior of proteins should not be made using water but wet polar organic liquids as solvents. 

Myelin in situ has a water content of about 40%. The dry mass of both CNS and PNS myelin is characterized by a high proportion of lipid (70-85%) and, consequently, a low proportion of protein (15-30%). By comparison, most biological membranes have a higher ratio of proteins to lipids. The currently accepted view of membrane structure is that of a lipid bilayer with integral membrane proteins embedded in the bilayer and other extrinsic proteins attached to one surface or the other by weaker linkages. Proteins and lipids are asymmetrically distributed in this bilayer, with only partial asymmetry of the lipids. The proposed molecular architecture of the layered membranes of compact myelin fits such a concept (Fig. 4-11). Models of compact myelin are based on data from electron microscopy, immunostaining, X-ray diffraction, surface probes studies, structural abnormalities in mutant mice, correlations between structure and composition in various species, and predictions of protein structure from sequencing information [4]. 

A = solv, pol. The striking similarity in the spectra and their components is evident, justifying the use of OKE data to model SD in this liquid. It should be noted that the two experiments have very (tifierent dynamical origins in some liquids such as, for example, water, where SD is strongly dominated by rotational dynamics, " whereas OKE probes mainly translational motions due to the very small molecular polarizability anisotropy. ... 

Extensive studies in reverse micelles revealed a similar water distribution [127-130], which is consistent with the distinct water model proposed by Finer [150]. For example, when the molar ratio (wo) of water to the surfactant is 6.8 in lecithin reverse micelles with a corresponding diameter of 37 A, three solvation time scales of 0.57 (13%), 14 (25%), and 320 ps (62%) were observed using coumarin 343 as the molecular probe. At w0 = 4.8 with a 30-A water core diameter, only a single solvation dynamic was observed at 217 ps, which indicates that all water molecules are well ordered inside the aqueous pool. The lecithin in these reverse micelles have charged headgroups, which have much stronger interactions with water than the neutral headgroups of monoolein in the... 

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