Site group

Off-site groups. Off-site training provides a concentrated focus and eliminates distractions. In addition, off-site meetings can often help promote a sense of teamwork among participants. 

The elucidation of the X-ray structure of chymotrypsin (Ref. 1) and in a later stage of subtilisin (Ref. 2) revealed an active site with three crucial groups (Fig. 7.1)-the active serine, a neighboring histidine, and a buried aspartic acid. These three residues are frequently called the catalytic triad, and are designated here as Aspc Hisc Serc (where c indicates a catalytic residue). The identification of the location of the active-site groups and intense biochemical studies led to several mechanistic proposals for the action of serine proteases (see, for example, Refs. 1 and 2). However, it appears that without some way of translating the structural information to reaction-potential surfaces it is hard to discriminate between different alternative mechanisms. Thus it is instructive to use the procedure introduced in previous chapters and to examine the feasibility of different... 

Fig. 7 shows the progressive transformation of montmorillonite to iliite/smectite interlayers by the gradual development of both the characteristic Cs and Rb high selectivity profiles observed for pure illite and the high Cs-Rb selectivity at+ race fadings. The data can be simulated (see table VI for the Ca - Cs case) using a consistent set of intrinsic selectivity coefficients and identical site group capacities for the Ca-Cs and... 

TABLE VI. InK values and site group capacities (meq 100/g) for simulating the Cs Ca equilibria at 25°6 of potassium-exchanged Camp Berteau montmorillonite subjected to alternate wettingdrying cycles... 

Highly selective exchange as related to the presence of crystallographically different site groups... 

Comparison between the population of Ag ions in each site group determined by X-ray diffraction techniques and calculated by use of the parameters given in fig. 8... 

The various possible site symmetries for the different point groups have been tabulated in several places 3, 19—21). The necessary correlation tables between point and site groups, which are used in discussions of the examples in this text are assembled in the Appendix. 

Ref. VI 2 V3 VA Space group Site group Factor group Stretching vibrations obs. theoret. Vi V3 VI V3 ... 

The vibration bands relative to phosphate groups in the apatite structure differ from the normal modes of the P04 isolated ion, due to distortions of the PO4 tetrahedra in the apatite lattice and vibrational coupling [4]. Therefore, site-group and factor-group analyses were applied [15,16,18,21] to elucidate the vibrational spectra observed (Fig. 5) and band assignments of infrared (IR) and Raman bands have been given (Table 3). 

The C02 hydration activity of cat isoenzyme III is independent of pH in the range of 5.0 < pH < 8.5 (148). The pKa value of zinc-H20 is outside this pH range and probably quite low due to electrostatic effects from positively charged active-site groups such as Lys-64 and Arg-67 (143). 

A change in the solvation of the active site (group of atoms at which the observed phenomenon occurs) due to steric effects exerted by an adjacent group. 

Figure 14-10 Models of catalytic intermediates for aspartate aminotransferase in a half-transamination reaction from aspartate to oxalocetate. For clarity, only a selection of the active site groups are shown. (A) Michaelis complex of PLP enzyme with aspartate. (B) Geminal diamine. (C) Ketimine intermediate. The circle indicates a bound water molecule. See Jansonius and Vincent in Jurnak and McPherson.163 Courtesy of J.N. Jansonius.

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