Hydrophobic molecular regions

Single molecules or micelles associate spontaneously in a thermodynamic equihbrium at a definite critical micelle concentration within a biocoUoidal system [47]. Analogously to micelle formation in liquid systems, aggregation of surfactants at a surface depends on a critical hemi-micellar concentration [48, 49]. The removal of the hydrophobic molecular region from the hydrophihc interface... 

In the previous sections, we discussed how ion pairing influences bulk electrolyte properties as well as controls where and how strongly ions bind to complex biomolecules. We also mentioned that large, soft anions can bind to aliphatic regions and we now focus on this mechanism that — perhaps counter intuitively — causes certain ions to be attracted to nonpolar or hydrophobic molecular regions. 

Hydrophobic interactions <40 Force is a complex phenomenon determined by the degree to which the structure of water is disordered as discrete hydrophobic molecules or molecular regions coalesce. 

Fig. 11 Plots of the measured lower critical solution temperature (LCST) as a function of the theoretical average number of OEGMA475 units per chain for a series of P(Me02MA-co-OEGMA475) copolymers of various composition. Hydrophobic and hydrophilic molecular regions on the copolymer are indicated in red and blue, respectively. (Reprinted with permission from [76]. Copyright (2008) John Wiley Sons, Inc.)...

Lipoproteins have hydrophobic core regions containing cholesteryl esters and triglycerides surrounded by unesterified cholesterol, phospholipids, and apoproteins. Certain lipoproteins contain very high-molecular-weight proteins that exist in two forms B-48, formed in the intestine and found in chylomicrons and their remnants and B-lOO, synthesized in liver and found in VLDL, VLDL remnants(IDL),LDL (formed from VLDL), and Lp(a) lipoproteins. HDL consist of at least 15 discrete molecular species. All species contain apolipoprotein A-I (apoA-I). Fifty-three other proteins are known to be distributed variously among the HDL species. 

Furthermore, rotational catalysis was proposed for the FO-ys-(aP)3-Fl complex [45]. This rotation might be electrically driven by the reversible ballistic proton mechanism, as follows. In ATP synthesis, each ADP-Pi loaded aP-site of the water exposed Fl head is bound in turn to the hydrophobic, topically bent, ys axis. This internal axis is inserted into the FO membrane component so as to form an effective channel for ballistic protons. The aP catalytic unit is comparable to a myosin head, while the biochemical role of the ys axis is quite similar to that of the actin filament in the enzymatic cycle (Scheme 2). Thus, in the direction of synthesis, the impact of a trans-membrane ballistic Fi+ within the hydrophobic catalytic region is proposed to drive three concomitant effects First, dehydration of the terminal phosphate bond results in ATP synthesis. Second, molecular recoil upon the FI+ impact dissociates the ys-aP complex. Third, the abrupt increase of electric charge at the hydrophobic site drives fast relative rotation at 120° towards hydrophobic ys interaction with the next, ADP-Pi loaded, aP-site. Simultaneous exchange of products and substrates, carried out at the other two, water exposed, aP sites, might electrically dictate ongoing rotation in the appropriate direction. 

Each molecular region of capsaicin has been analyzed by means of systematic structural studies of the pungent and antinociceptive SARs. These studies revealed that capsaicin, dihydrocapsaicin, and V-vaniUyloctylamide (Fig. 3) are approximately equipotent, suggesting that either the overall size or the hydrophobicity (or both) are more important than the double bond and the branched side chain. Variation on fatty acid length, from C to Cn,... 

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