Surface phenomena, electrostatic interactions

The effect of electrolyte concentration suggests binding in the adsorbed layer (protein-surface and perhaps protein-protein) is an attractive electrostatic phenomenon, since interactions of this type would be expected to diminish through the charge... 

The question may he asked how is this behavior modified at the electrochemical interface. That is, water molecule chemisorption may be sensitive to the presence of local electric fields or variations in the apphed electrochemical potential as a result of the molecular dipole. The response of water molecules to such a field has heen simulated hy Sanchez [63]. Variations in the local charge density on a cluster model for Ag(lll) were used to investigate this phenomenon. Polarization of the surface to 15 pC/cm was observed to produce a standing structure in which water molecules are hound via the oxygen atom, with the hydrogen atoms directed away fiom the surface in the normal direction. Consequently, the phenomenon known as dielectric saturation ensues, in which there exists a reduced dielectric constant at the interface, and, hence, electrostatic interactions across the metal/aque-ous interface become enhanced. 

In contrast to membrane filtration, in which adsorption is an undesirable phenomenon because of the possible loss of target substance, membrane adsorption is in fact based on this phenomenon and high sorption capacities improve in this case the efficiency of the operation from the economical point of view. However, virtually all membrane materials (surfaces), even the ones designed primarily with membrane filtration in mind, exhibit a more or less pronounced but nonspecific adsorption tendency, due to the general possibility of establishing hydrophobic, dipole-dipole and electrostatic interactions as well as hydrogen bonds with the various dissolved molecules. It was also observed by many investigators that mechanical filter may retain particles/molecules that are smaller than the filter s pores, presumably as a result of an impaction of the particles on the filter surface. However, whatever the cause, if the forces... 

The electrostatic interaction between charged molecules and oppositely charged surfaces is an effective approach exploited in molecular recognition phenomenon. For example, cytochrome c, which carries eight positive charges, is attracted toward cytochrome c... 

Biosorption is a process where metal ions (or metalloid species), compoimds and particulate substances are removed from solution by biological material through adsorption of the contaminant on a surface site of the biomass. It can be by physical forces (e.g. van der Waals, electrostatic interaction) and/or involving a chemical reaction. It is believed that biosorption using dead biomass is based on the physical sorption phenomenon, whereas sorption using live biomass occurs through both physical and chemical processes as well as transmembrane transport and accumulation of heavy metals in the algal cell. ... 

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