Hydrophobic recognition

Figure 8. Synthetic substrates GPANA and BTPNA. Open arrows indicate amide bond hydrolyzed by a-chymotrypsin. Solid arrows indicate hydrophobic recognition groups. Numbers refer to protons examined by NMR.

On the contrary, poly(l-leucine) does not offer a chance to provide this interaction because the residual isobutyl groups are too bulky to approach each other (Fig. 8B). Also, it should be noted that poly(r-leucine) provides only a-helices, even on silica and, thus, their carbonyl groups are absolutely covered with the bulky residual groups. As a result, the poly(L-leucine) phase showed only hydrophobicity recognition similar to ODS. The selectivity is close to that in ODS (o =1.5). 

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. 

III.B) and the effect was primarily attributed to the hydrophobic recognition of the long alkyl chains. 

Remarkable temperature dependence on separation factors are also observed for this sample set. As shown in Fig. 9, the selectivity is significantly higher at the crystalline temperature of Sil-to-ODA than at the isotropic temperature. On the other hand, ODS shows no significant temperature dependence. Therefore, the enhanced selectivity at the crystalline temperature cannot be explained by only hydrophobicity recognition. It is known that planar compounds, such as triphenylene, are more strongly incorporated into an oriented medium than nonplanar compounds, such as o-terphenyl. It was reported by us that that a-helical... 

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