Transport properties hydrogen hydrates

The aqueous surface is in equilibrium with the vapor pressure of water in the atmosphere. As a result, the effect of anlistats is a function of relative humidity. No comparative data on effectiveness of antistatic additives is meaningful without reference to relative humidity. In addition, many additives that arc effective at 50 percent or higher RH become useless at very low RH. It is very difficult to quantify the exact dependence of antistatic activity on relative humidity. The form of the equation relating dissipation of charge to moist air is known to be exponential. The relationship of charge transport properties of hydrated protons in hydrogen bonded smface networks to relative humidity can, however, only be guessed aL... 

Abresch et aL, 1998] and of the lumen-side domain of cytochrome/[Martinez et al., 1996]. Finally, in cytochrome c oxidase, two independent theoretical studies have predicted the hydration of buried cavities implicated in the uptake of protons [Riistama et al, 1997 Hofacker and Schulten, 1998]. Although these water molecules were not resolved in published crystallographic structures of the P. denitrificans [Iwata et al, 1995] and bovine heart [Tsukihara et al, 1996] enzymes, many of them are well-defined in a new structure of the Rb, sphaeroides enzyme [M. Svensson-Ek, personal communication]. Understanding the molecular properties giving rise to proton transport in hydrogen-bonded networks containing water molecules is therefore an important step towards the elucidation of proton-pumping mechanisms. 

In experiments, the percolation transition of hydration water can be detected by conductivity and dielectric measurements. Formation of a condensed hydrogen-bonded network of water should provide a media for the charge transport (proton or ions) and should change qualitatively the dielectric properties of the system. Sharp stepwise increase of the conductivity of the system with increasing water content at some threshold hydration level may directly indicate the appearance of an infinite hydrogen-bonded water network via a percolation transition. The dielectric response is also expected to increase drastically at the percolation threshold. Note, however, that the strongly attractive sites on the surface, which immobilize water molecules, may complicate interpretation of the results. As these effects occur on the surfaces, their experimental observation is possible first in the system with high surface/volume ratio (in various porous media). 

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