Hydrophobic recognition site

Capped cyclodextrin, I, is also very helpful for preparation of regionspecifically bifunctionalized cyclodextrin (VI) via successive Sjj2 reaction with X" and Y (7). Compounds of this type are important to mimic a variety of enzymes since they have a hydrophobic recognition site as well as a bifunctional catalytic site (X...Y) which is very often encountered in native enzyme mechanisms. 

The solvent used in the oxidation described here is aqueous acetonitrile. Therefore, hydrophobic interaction 30> may operate between the recognition sites. 

Molecular imprinting can be accomplished in two ways (a), the self assembly approach and (b), the preorganisation approach3. The first involves host guest complexes produced from weak intermolecular interactions (such as ionic or hydrophobic interaction, hydrogen bonding) between the analyte molecule and the functional monomers. The self assembled complexes are spontaneously formed in the liquid phase and are sterically fixed by polymerisation. After extraction of the analyte, vacant recognition sites specific for the imprint are established. Monomers used for self assembly are methacrylic acid, vinylpyridine and dimethylamino methacrylate. 

Enzyme models 18 and 19, which catalyze the decarboxylation, are typical examples of double recognition (87). These metalloenzyme models recognize a-ketoacid as the specific substrate by the hydrophobic interaction and coordination interaction as shown in Fig. 24 and Table XVII. Thus, the presence of the second recognition site, triamino-Zn2+, results in an increase... 

Carboxypeptidase A"" (CPA, EC 3.4.17.1) is a proteolytic enzyme that cleaves C-terminal amino acid residues with hydrophobic side chains selectively. Several X-ray structures are available" The active site of CPA consists of a hydrophobic pocket (primary substrate recognition site) that is primarily responsible for the substrate specificity, a guanidinium moiety of Argl45 that forms hydrogen bonds to the carboxylate of the substrate, and Glu270, whose carboxylate plays a critical role, functioning either as a nucleophile to attack the scissUe carboxamide carbonyl carbon of the substrate or as a base to activate the zinc-bound water molecule, which in turn attacks the scissile peptide bond ". However, semiempirical calculations had shown that the direct attack of... 

When complexation was carried out in MeOH, a 1 1 1 complex of the host, (—)-37 and MeOH was formed. Distillation in vacuo gave (—)-37 in 42% ee and 44% yield. In the case of complexes formed by the host 28, the large hydrophobic void space can competitively include a disordered toluene molecule or (—)-cyanohydrin [48], (S,S)-(—)-6, which in the solid state forms much smaller hydrophobic cavities, could not resolve rac-36 in either solvent. Under the same conditions, however, it successfully resolved rac 3-acetylcyclohex-2-enol, 38, forming 1 2 complexes in both solvents. From these (+)-38 was obtained in 40 % ee and 86 % yield, and 66 % ee and 79 % yield, respectively, from toluene and MeOH solutions. The above cases suggest that each of the hosts (28, 34 and 35) contains two recognition sites-one enantioselective, located around sterically hindered OH groups, and the other nonspecific, and located in the hydrophobic cavity. If molecules of one enantiomer and a solvent compete for the enantioselective recognition site (with H-bond formation), the enantioselectivity of the host... 

Another important area of dynamic studies in biological samples is the effect of hydration upon molecular mobility in proteins and carbohydrates. The reason for these studies is primarily that protein dynamics, in particular, are crucial to their function, and so examining factors, such as the degree of hydration, that affect their dynamics is very important. However, it is obviously near-impossible to study dynamics in aqueous solution as a function of degree of hydration, and, since most proteins are not soluble in nonaqueous solvents, solid-state studies must be used. The motions at three methionine (Met) residues in Streptomyces subtilisin inhibitor (SSI) were studied with 2H NMR using a sample in which the Met residues at two crucial enzyme recognition sites (PI and P4) were specifically deuterated, along with one in the hydrophobic core.114 The motions of the Met side-chains were then examined... 

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