Surface patches

The SCLl surface is particularly interesting. Although the outer and the inner surface look different in Fig. 8(a), they have the same surface area. In fact they are built of the same piece of the surface. The picture of 1/8 of the unit cell, see Fig. 8(b), explains how two different periodic surfaces can be built of the same surface patch. 

The processes described and their kinetics is of importance in the accumulation of trace metals by calcite in sediments and lakes (Delaney and Boyle, 1987) but also of relevance in the transport and retention of trace metals in calcareous aquifers. Fuller and Davis (1987) investigated the sorption by calcareous aquifer sand they found that after 24 hours the rate of Cd2+ sorption was constant and controlled by the rate of surface precipitation. Clean grains of primary minerals, e.g., quartz and alumino silicates, sorbed less Cd2+ than grains which had surface patches of secondary minerals, e.g., carbonates, iron and manganese oxides. Fig. 6.11 gives data (time sequence) on electron spin resonance spectra of Mn2+ on FeC03(s). 

More subtle factors that might affect k will be the sites structures, their relative orientation and the nature of the intervening medium. That these are important is obvious if one examines the data for the two copper proteins plastocyanin and azurin. Despite very similar separation of the redox sites and the driving force (Table 5.12), the electron transfer rate constant within plastocyanin is very much the lesser (it may be zero). See Prob. 16. In striking contrast, small oxidants are able to attach to surface patches on plastocyanin which are more favorably disposed with respect to electron transfer to and from the Cu, which is about 14 A distant. It can be assessed that internal electron transfer rate constants are =30s for Co(phen)3+, >5 x 10 s for Ru(NH3)jimid and 3.0 x 10 s for Ru(bpy)3 , Refs. 119 and 129. In the last case the excited state Ru(bpy)3 is believed to bind about 10-12 A from the Cu center. Electron transfer occurs both from this remote site as well as by attack of Ru(bpy)j+ adjacent to the Cu site. At high protein concentration, electron transfer occurs solely through the remote pathway. 

Fig. 16. Cacodylate binding site between NCP molecules. Figure shows details of the stacking interactions between two neighboring molecules involving the dorsal H3 H4 tetramer face of one NCP and the ventral H2A H2B dimer face an adjacent NCP. The acidic residues forming a surface patch on the dimer face are rendered in ball-and-stick. The H4 tail is in blue and the H3 region involved in the interaction is in yellow. The cacodylate is shown as a CPK rendering.

The boundary surface of a region in space is an important physical quantity. The integral of a field in the region is related by the fundamental theorem of calculus to an integral over its boundary surface. A surface integral can be approximated by summing quantities associated with a subdivision of the surface into patches. In the present work, the surface patches are taken to be the (approximate) exposed surface area of atom in a molecule. 

Surface aggregates formed by ionic surfactant adsorption on oppositely charge surfaces have been shown to be bi layered structures (1.) and are called admicelles<2) in this paper, though they are sometimes referred to as hemimicelles. The concentration at which admicelles first form on the most energetic surface patch is called the Critical Admicellar Concentration (CAC) in analogy to the Critical Micelle Concentration (CMC), where micelles are first formed. Again, in much of the literature, the CAC is referred to as the Hemimicellar Concentration (HMC). 

Fischer, W. Koch, E. 1989a New surface patches of minimal balance surfaces. I. Branched catenoids. Acta crystallogr. A 45, 166-169. 

Breaking a triboluminescent crystal separates charge across the growing crack or between surface patches. 

Given conditions where 0 is small for every surface patch at a given pressure, Equation 8 reduces to... 

A feature that appears to be common to several of the proteins is a hydrophobic surface patch at the northern end... 

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