Hydrophobic groups competition with

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]. 

The observed chaige reversal can prove the presence of two types of the PE adsorption sites on the capillary surface. At low concentration, the electrostatic adsorption of positively charged PE molecules predominantly occurs on the negatively charged sites of quartz surface. Thereafter (or simultaneously), on the surface of a capillary covered with a polymer adsorbed layer, the adsorption of the PE molecules can occur due to the forces of molecular attraction and attraction between hydrophobic sites of polyelectrolyte and surface (e.g. siloxane groups). Their competition with the electrostatic repulsion forces that increase in the course of further adsorption of PE molecules determines the completion of the adsorption and the formation of equilibrium (with the solution) adsorbed layer. 

All statins share an HMG-like moiety which is linked to rigid hydrophobic groups (Figure 12.3). Lovastatin and simvastatin are lactone prodrugs which are converted to the active open hydroxyl acid form in the hver. Enzyme studies show that the statins are competitive inhibitors of HMGR with respect to HMG-CoA and have K values in the 0.1-2.3 nM range [62]. Crystal structure studies have revealed that the statins occupy the active site where HMG-CoA binds but do not affect NADPH binding [63]. 

In cellulose triacetate virtually all the hydroxyl groups in the cellulose have been acetylated and this makes the fibre more hydrophobic and, therefore, less receptive to dye molecules. Triacetate differs from secondary cellulose acetate in that it can be heat set, making it in this respect competitive with the true synthetic fibres. Steam setting is made difficult because tried extends slightly during the process, unlike the synthetic fibres which contract. This adds to the difficulty of fixing dimensions and may cause a ripple effect in the warp direction. For this reason dry-heat setting is preferred because it is not accompanied by extension. 

Figure 5.29. Stretch-induced pKa shift within hydrophobically associated elastic model protein implies competition for hydration between carboxy-late and hydrophobic groups. Despite water uptake into the model elastic protein on stretching, the COO" experiences less accessible hydration. The implication is that hydrophobic hydration, formed due to exposed hydrophobic groups on extension, is unsuited for COO" hydration. (Reproduced with permission from Urry et al. )...

The apolar-polar repulsive free energy of hydration, AG,p, as reviewed above, results from a competition for hydration between charged species and hydrophobic groups. In the most extreme case reported thus far, this competition raised the pKa of a carboxyl from about 4 to about 11. This constitutes an amount sufficient to raise the free energy of carboxylates by 8 to lOkcal/mole. The basic issue to be addressed here is whether there is reason to believe that the free energy of the phosphate group would also be subject to competition for hydration with hydrophobic groups. 

---