Bulky hydrophobes

There is one exception to the rule that requires bulky hydrophobic residues to fill the interior of eight-stranded a/p barrels in order to form a tightly packed hydrophobic core. The coenzyme Biz-dependent enzyme methylmalonyl-coenzyme A mutase, the x-ray structure of which was determined by Phil Evans and colleagues at the MRC Laboratory of Molecular... 

Reichert, W.L., French, B.L, and Stein, J.E. et al. (1991). 32P postlabelling analysis of the persistence of bulky hydrophobic xenobiotic-DNA adducts in the liver of English sole, a marine fish. In Proceedings of the 82nd Meeting of the American Association for Cancer Research, Houston, TXP, 87. 

Type II drugs these consist of bulky hydrophobic compounds, such as d-... 

A few synthetic helical polymers are known to act as chiral selectors.7a,918d l8k i9d i9h ancj are widely used as chiral stationary phases (CSP) in gas or liquid chromatography.73,53 Recently, it has been reported that the preference of one helical sense in isotropic solution can be induced by some interaction between optically inactive polymers and chiral solvents/additives. Examples of this include poly(n-hexyl isocyanate)18d l8k and poly(phenylacetylene)s bearing functional group.19d 19h The polysilane derivatives also show chiral recognition ability in solution at room temperature. Poly(methyl-ft-pinanylsilane) includes two chiral centers per bulky hydrophobic pinanyl side group28 and... 

Reversible, non-competitive inhibition of polymerase is also afforded by a series of N-benzoyl pyrrolidines. Substitution on the benzoyl moiety with a para-trifluoromethyl group is optimal in this series. Bulky, hydrophobic groups at the 2-position of the pyrrolidine ring increase activity, and the 5-position tolerates a wide range of substituents, indicative of a solvent exposed portion of the inhibitor. Compound (+)-38, containing a 2-thienyl moiety at the 5-position, has an IC50 of 190 nM in the enzyme assay while its enantiomer is almost 100-fold less active [83]. 

Liquid-liquid extraction is a form of solvent extraction in which the solvents produce two immiscible liquid phases. The separation of analytes from the liquid matrix occurs when the analyte partitions from the matrix-liquid phase to the other. The partition of analytes between the two phases is based on their solubilities when equilibrium is reached. Usually, one of the phases is aqueous and the other is an immiscible organic solvent. Large, bulky hydrophobic molecules like to partition into an organic solvent, while polar and/or ionic compounds prefer the aqueous phase. 

PEGs also showed enhanced stability similar to that of ph-PEG. PEG containing hydroquinone substitutions showed a decrease in critical chain length but again not as drastically as the naph-PEG because the bulky hydrophobic group on the hydroquinone is in the middle of the chain while that of the 1-naphthol is on the end of the chain. Thus the effects of hydrophobic interactions have been shown to be a universal stabilizing factor in interpolymer complexation. 

This class of E3 enzymes recognizes the nature of the N-terminus of target proteins. As shown by Varshavsky (1992), yeast proteins may be selected for ubiquitinylation according to the N-end rule . Proteins containing basic or bulky-hydrophobic amino acids at the N-terminus are recognized by distinct N-end rule E3 enzymes of which the E3a enzyme (UBRl protein in yeast) is best characterized. 

Bulky hydrophobic Leu side chains of M2 helices close the channel. 

Portions of the statins (shown In blue) clearly resemble HMG-CoA. However, the bulky hydrophobic groups of the inhibitors differ from the CoA moiety of the substrate. 

Further improvement of the map with these phases may reveal side chains more clearly. Now the trick is to identify some specific side chains so that the known amino-acid sequence of the protein can be aligned with visible features in the map. As mentioned earlier, chain termini are often ill-defined, so we need a foothold for alignment of sequence with map where the map is sharp. Many times the key is a short stretch of sequence containing several bulky hydrophobic residues, like Trp, Phe, and Tyr. Because they are hydro-phobic, they are likely to be in the interior where the map is clearer. Because they are bulky, their side-chain density is more likely to be identifiable. From such a foothold, the detailed model building can begin. 

Functionalisation with bulky hydrophobic carboxylic acids/DCC was studied for the synthesis of amphiphilic polymers based on dextran. Bile acid is covalently bound to dextran (Fig. 27) through ester linkage in the presence of DCC/DMAP (added in dichloromethane) as coupling reagent. 

All lipases of this family are characterized by a helical lid that covers the active site (Kg. 9X It has been hypothesized [145] that this lid moves away in a hydrophobic environment, thereby making the active site accessible to the lipid substrate. In this hypothesis an important role has been reserved for the bulky tryptophane residue at position 117 in the center of the helical lid. In the Rhizoptts javwicus lipase, however, this bulky hydrophobic residue is replaced by a alanine, and no other bulky residue seems located so that it could take die role of residue 117. Therefore, it was concluded that the lipid-interaction model that haa been suggested for this class of lipase is not generally applicable in all its details. 

---