Changes in the State of Hydration

When the surfaces of the protein molecules and the sorbent are predominantly polar, it is probable that some hydration water is retained between the adsorbed protein layer and the sorbent surface. Then, the contribution from changes in the state of hydration to the Gibbs energy of protein adsorption, AadsGhydr, will be minor. When the surfaces are... 

One of the most important functions of the normal kidney is its ability to respond to changes in the state of hydration by excreting dilute or concentrated urine. Appropriate water excretion or retention provides a very sensitive measure of general renal integrity. 

In dilute aqueous solutions, biomolecules are completely covered by water molecules. The structure of water near a boundary essentially differs from the structure of bulk water (see Sections 2 and 5). Specific water structure is seen in one or two water layers near hydrophilic surfaces, whereas the rest of liquid water is bulk-like. This is also the case for the surfaces of biomolecules, which allow consideration of hydration water as a separate subsystem. Conformational transitions and aggregation of biomolecules occur in dilute solution due to variations of temperature and/or pressure and due to additions of some cosolvents. It is natural to expect that these biologically important processes are related to the changes in the state of hydration water shell. First, we consider the effect of heating on the state of hydration water shell and on the properties of biomolecules. Then, we discuss the dynamic transition of biomolecules and pressure-induced denaturation in relation with the liquid-liquid transitions of hydration water. 

It should be noted that the valence of chromium is 6, both in chromate and dichromate. The difference between manganate and permanganate lies in the changing valence of the manganese. The difference between chromate and dichromate lies merely in the state of hydration and can be referred back to the acids. 

Hydration of HPP. All factors mentioned above affect the T i value, showing the change in the state of water to be the result of a change in the composition of the water and the surface properties of the disperse phase. Aluminium hydrolysis products are mostly particles of Al(OH)3 with aluminium hydroxyl complexes adsorbed on them, so the change in T can be associated with an altered nature and number of hydrophilic centres. It has been shown5,6 that in all cases the spin-spin relaxation time of water protons decreases with increasing OH/A1 ratio in the coagulant molecule. This is an evidence of increased hydration of particles surface in this direction. 

It is therefore assumed that the p-variation in hydration comes only from a thermodynamic effect, related to a Y-dependent change in the stability of the intermediate, whereas in bromination, a transition-state shift adds to this latter effect, as expressed by (49) and (52), where log kY expresses the reactivity of PhCY=CH2. The second term in (52) is probably negligible in hydration... 

The validity of the assumption that the various thermodynamic properties of the smectite remain invariant, regardless of the state of hydration, has been addressed in detail by Sposito and Prost (1). They point out that one would, for example, expect hydrolysis of the clay to occur at high water contents, and also, it is likely that the exchangeable cations will change their spatial relationship with the clay layers. Thus, the derived thermodynamic properties of the adsorbed water would not represent correct values. 

We consider dehydration-adsorption of hydrated protons (cathodic proton transfer) and desorption-hydration of adsorbed protons (anodic proton transfer) on the interface of semiconductor electrodes. Since these adsorption and desorption of protons are ion transfer processes across the compact layer at the interface of semiconductor electrodes, the adsorption-desorption equilibrium is expressed as a function of the potential of the compact layer in the same way as Eqns. 9-60 and 9-61. In contrast to metal electrodes where changes with the electrode potential, semiconductor electrodes in the state of band edge level pinning maintain the potential d(hi of the compact layer constant and independent of the electrode potential. The concentration of adsorbed protons, Ch , is then determined not by the electrode potential but by the concentration of h3 ated protons in aqueous solutions. 

The adsorption process is often entropically driven with the gain in entropy arising from dehydration of the adsorbent surface and structural rearrangements inside the protein molecule (the state of hydration and field overlap changes inside the adsorbed protein included). 

Protein function at solid-liquid interfaces holds a structural and a dynamic perspective [31]. The structural perspective addresses macroscopic adsorption, molecular interactions between the protein and the surface, collective interactions between the individual adsorbed protein molecules, and changes in the conformational and hydration states of the protein molecules induced by these physical interactions. Interactions caused by protein adsorption are mostly non-covalent but strong enough to cause drastic functional transformations. All these features are, moreover, affected by the double layer and the electrode potential at electrochemical interfaces. Factors that determine protein adsorption patterns have been discussed in detail recently, both in the broad context of solute proteins at solid surfaces [31], and in specific contexts of interfacial metalloprotein electrochemistry [34]. Some important elements that can also be modelled in suitable detail would be ... 

Solvation of DNA bases/base pairs is of fundamental importance to biological processes as they take place in aqueous media. The effect of hydration on neutral bases or base pairs has been addressed using quantum chemical methods [106-112] as well as molecular dynamics (MD) simulations [113, 114], It is known that unlike the gas phase, dipole bound anions do not exist in condensed environments because such diffuse states are destabilized in the aqueous phase [115]. The drastic change in the nature of excess electron binding in the presence of water molecules with uracil has been observed experimentally by Bowen and co-workers [95b] using negative electron photoelectron spectroscopy (PES). They observed that even with a single water molecule the dipole bound state of uracil anion in gas phase... 

We can reasonably assume two major contributions to the difference in specific volume between the unfolded and folded states of a protein. The first contribution is that arising from the decrease in solvent-excluded volume when the tightly, but of course not perfectly, packed protein folded structure is disrupted. Water molecules enter this volume, thereby decreasing the overall volume of the protein solvent system. The magnitude of this contribution is a specific property of the protein, both in its folded and unfolded state. The second contribution arises from the change in the volume of the water molecules that hydrate the newly exposed protein surface area, relative to their volume in the bulk. Much of our present understanding of the contribution of differential hydration volume has come from recent studies of model compounds and proteins based on PPC. This technique, developed by Brandts and coworkers [17] and recently reviewed by us [16,18], is based on the measurement of the heat released or absorbed upon small (e.g., 0.5 MPa) pressure... 

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