Electrostatic Facilitation

Binding of small anions to positively charged groups in or near 

These more chemical investigations were complemented by the biophysical studies and X-ray cristallographic analyse A precise knowledge on the catalytic 

The catalytic cycle starts with the replacement of a water molecule at the axial position by superoxide (Fig. 12). 

Although zinc seems to enhance the reactivity by this mechanism it is not essential for the reactivity of SOD, because at pH 7 the imidazolate nitrogen without zinc will be at least partially protonated. This would comprehensively explain, why in contrast 

Replacement of the catalytically active copper by other metals results in an inactive enzyme There is, however, strong evidence from a newer pulse radiolytic 

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A plausible rationale for the above Mg2+ ion catalysis may be electrostatic facilitation of nucleophilic attack to form a pentacovalent intermediate as depicted in the structures of Figure 12. This rationale already has been proposed by Steffens et al. for the metal ion catalysis in the intramolecular displacement reaction of phenolate ion by car-boxylate (17). 

Levy, Y., Onuchic, J.N., Wolynes, P.G. Fly-casting in protein-DNA binding Frustration between protein folding and electrostatics facilitates target recognition. J. Am. Chem. Soc. 2007, 129,... 

SODs are differentiated mainly by the redox-active metal in the active site copper, manganese, or iron. The iron and manganese SODs are structurally similar (5-11) and are structurally distinct from the Cu,Zn SOD (12). The dramatic features of these enzymes are that they catalytically dismutate superoxide at rates that are not only diffusion controlled but have been shown to be electrostatically facilitated (13). In these systems, modifications of amino acid residues near the active site have been shown to alter the enzymatic activity, indicating that superoxide is electrostatically drawn into the active site channel (14). In addition, in contrast to the spontaneous dismutation rate of 02 and the dismutation rates of 02 by many metal complexes, all of which are pH dependent, the enzymatic dismutation rate is largely pH independent over the pH range (5-10). 

The synthesis and structural correlations of (448) and the reference compound (449) have been described, and arguments presented that the effect of ionization of the endo-carboxylic acid group on the hydrolysis of (448) represents a reasonable model for the effect of aspartic acid-52 of lysozyme on the hydrolysis of saccharides by the enzyme. However, on the basis of kinetic studies of the hydrolysis, it is concluded that electrostatic facilitation of general acid-catalysed a-oxonium ion formation is not significant, and hence is probably unimportant in lysozyme. ... 

It provides electrostatic stabilization of the carbanion formed upon removal of the C-2 proton. (The sf hybridization and the availability of vacant d orbitals on the adjacent sulfur probably also facilitate proton removal at C-2.)... 

What properties oibenzyltriethylammonium ion make it soluble in diverse solvents Examine its electrostatic potential map and atomic charges. Which groups facilitate water solubility Explain. Which groups facilitate chloroform solubility Explain. 

Electrostatic hand guns The same principle has been adopted on portable hand guns. These modifications facilitate the coating of electrically shaded areas. 

Note 5 In calculating paint requirements up to 50% more than the theoretical dry film weight requirement should be allowed to cover thick coatings, wastage, repairs, losses (typically 30% for air spray 15% airless spray 10% electrostatic spray 5% roller or brush) etc. Manufacturers should be asked to quote percentage volume solids in their paint to facilitate calculations. 

In pressing, the threshold concentration of the filler amounts to about 0.5% of volume. The resulting distribution of the filler corresponds, apparently, to the model of mixing of spherical particles of the polymer (with radius Rp) and filler (with radius Rm) for Rp > Rm as the size of carbon black particles is usually about 1000 A [19]. During this mixing, the filler, because of electrostatical interaction, is distributed mainly on the surface of polymer particles which facilitates the forming of conducting chains and entails low values of the percolation threshold. 

Most polymers are very good electrical insulating materials because of their chemical composition, i.e., their electrical conductivity is exceptionally low. Because of this important property, many plastics are used to produce electrically nonconductive parts. However, the high surface resistance leads to an unwanted property the material is prone to electrostatic charge accumulation. To facilitate dissipation of the charge, antistatic agents are incorporated, which combine with atmospheric moisture on the plastic surface to form a conductive film. 

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