Hydrophobic interaction results Definition

A simple example is one where the hydrophobic interactions result in < i for all > 1, but the packing constraints on the chains and heads result in a minimum energy for a finite value of N = M (i.e., m < for N Af). (Below, a curvature energy model is discussed this model can also be used to motivate, but not to calculate in detail, a study of micellar sizes and shapes.) If this minimum is deep n rises sharply compared to ksT around N = Af), the distribution of micelles will be nearly monodisperse. In this approximation, one can consider monomers and micelles of aggregation number Af only. At small values of 4>s (or equivalently, at small values of fi). Pi Pm (Af > 1) almost all the surfactant exists as monomers and the number of micelles is exponentially small. The requirement that all amphiphiles have the same chemical potential in equilibrium, Eq. (8.2) and the definition of the CMC (where Pi = Pi, Pm = Pmc ft = = c) allows us to calculate... 

Because of the kidney s involvement in the excretion of hydrophilic compounds and because most of the substrates of P-gp are hydrophobic compounds that are likely to be cleared mainly by biliary excretion or intestinal secretion, comparably fewer studies have been performed with the isolated perfused kidney. The isolated perfused rat kidney model was used to demonstrate that digoxin is actively secreted by P-gp located on the luminal membrane of renal tubular epithelial cells and that clinically important interactions with qui-nidine and verapamil are caused by the inhibition of P-gp activity in the kidney (332). These results provide an excellent example of how the isolated perfused kidney model can be used to definitively conclude that P-gp-mediated efflux is involved in the renal excretion of a compound and also to elucidate possible DDIs that might arise in the kidney following coadministration of P-gp sub strates/inhibitors. 

A new class of water soluble cellulosic polymers currently receiving attention Is characterized by structures with hydrophobic moieties. Such polymers exhibit definite surface activity at alr-llquld and liquid-liquid Interfaces. By virtue of their hydrophobic groups, they also exhibit Interesting association characteristics In solution. In this paper, results are presented on the solution and Interfaclal properties of a cationic cellulosic polymer with hydrophobic groups and Its Interactions with conventional surfactants are discussed. 

Polarity may be qualitatively defined as the ability of a solute to dissolve in a polar solvent, which results from interaction with surrounding molecules by dipolar, non-dispersive forces. By this definition, hydrocarbons are nonpolar because they possesses no permanent dipole moments, and the entire molecular surface must solely interact with its environment via dispersion forces. Thus methanol is more polar than octanol because the surface area of methanol that interacts only via dispersion forces (hydrophobic surface area) is much less than that of octanol. For liquids, increasing solute polarity generally causes an increase in water solubility. This is not necessarily true for solids because polarity... 

Aromatic molecules are hydrophobic but their thermodynamic hydration parameters are essentially different from those of aliphatic hydrocarbons (Table 2.5). The data in this table reveal that for benzene and toluene the A Gtr values are negative, primarily resulting from less unfavorable A Str values. Advanced MD simulations of the hydration of benzene and cyclohexane have shown that there is a definite tendency for H-bond interactions of the waters with the tt-electron system of the aromatics. This is confirmed by the solubility... 

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