Surface-bound water

Lewis bound form with a strong band at 1440 cm together with a weak 1490cm band. This implies that the Bronsted acidity is associated with the strongly bound water and as this water is removed the pyridine becomes coordinated to a Lewis bound site either nearby or at the undercoordinated A1 site produced by the removal of surface bound water. This transformation of Bronsted to Lewis acid centres is well established in catalyst chemistry as the sample... 

Sepiolite clay (<100 mesh) was heated in air at 120°C in order to remove the zeolitic and surface bound water molecules. The partially dehydrated clay mineral was subsequently exposed to acetone vapor at room temperature for a period of four days. H and 29Si CP MAS-NMR experiments revealed that the acetone molecules penetrated into the microporous channels of the sepiolite structure. Broad line 2H NMR studies using acetone-d6 revealed that, in addition to fast methyl group rotations, the guest acetone-d6 molecules were also undergoing 2-fold re-orientations about the carbonyl bond. The presence of acetone-d6 molecules adsorbed on the exterior surfaces of the sepiolite crystals was also detected at room temperature. 

If the adsorption of neutral halogen atoms occurs on the surface cation sites with replacing surface-bound water, then the amount of the adsorbed intermediates will be high in acidic solutions, as implied by Eq 6, resulting in an increase in apparent reactivity of halide ions with decreasing pH values. 

Many more-sophisticated models have been put forth to describe electrokinetic phenomena at surfaces. Considerations have included distance of closest approach of counterions, conduction behind the shear plane, specific adsorption of electrolyte ions, variability of permittivity and viscosity in the electrical double layer, discreteness of charge on the surface, surface roughness, surface porosity, and surface-bound water [7], Perhaps the most commonly used model has been the Gouy-Chapman-Stem-Grahame model 8]. This model separates the counterion region into a compact, surface-bound Stern" layer, wherein potential decays linearly, and a diffuse region that obeys the Poisson-Boltzmann relation. 

Because of the high photooxidative reactivity of Ti02, deriving from the high positive potential of a valence-band hole, even water can be oxidized on irradiated Ti02. In aqueous solutions, therefore, direct oxidation of an adsorbed substrate must compete with solvent oxidation [31], The formation of hydroxyl radicals by single-electron oxidation of surface-bound water is usually the dominant process in water, with the radical having been detected by EPR spectroscopy [32-34] and implicated by isotope effects [35]. 

In section 2.1 the contact interface between TBP and the minor groove of DNA was characterized as anhydrous. This is a common characteristic in all the TBP-DNA complexes available to date. As TBP presents a primarily hydrophobic surface to DNA, most of the hydrogen bond donors and acceptors at this surface are not satisfied by the complexation. Hence, there is likely to be an enthalpic penalty associated with the dehydration of this surface. This penalty is compensated by the favorable increase in entropy associated with the liberation of the surface-bound water molecules into bulk solution. Following this reasoning, there are two aspects of hydration that could contribute to the determination of sequence specificity the ideal sequence would be one which coordinates a large number of water molecules, but binds them least tightly. 

Thus a second possible explanation for the variation in bound water content is suggested. If water is prevented from freezing not only by Interaction with the bulk polymeric phase, but also by surface interactions, a linear dependence of bound water on membrane surface area would be expected. The intercept of the line would be the amount of water bound by bulk polymer, and the amount of "surface-bound" water would be obtained from the slope. Figure 10 is a plot of bound water vs. membrane surface area for the four copolyoxamide films used in this work. The data are very limited, but they do fit the best straight line with a correlation coefficient of 0.99. The best intercept is 0.32 g/g, suggesting that the bulk polymer binds... 

Depending on the cationic charge of the retention aid, fibre-surface bound water can be removed via charge competition by the retention aid. 

Protein surface Bound water relaxation Side chain rotational correlation Proton transfer reaction of ionizable side chains Protein conformation Local motion Isomerization process Folding-unfolding transition Enzyme substrate complex in solution Encounter rate... 

---