Polar and nonpolar region

Many a helices have predominantly hydrophobic R groups on one side of the axis of the helix and predominantly hydrophilic ones on the other. These amphi-pathic helices are well adapted to the formation of interfaces between polar and nonpolar regions such as the hydrophobic interior of a protein and its aqueous envi-... 

An important extension of lipid-solute interaction components [20] to membrane partitioning is provided by solute molecular structure. Spacing between polar and nonpolar regions (Fig. 8) within a solute molecule may result in significant distortion of the KpDm product across the membrane polar headgroup/lipid core interface [21], Such interactions may be responsible for deviations from projected transport predictions based on simple partitioning theory translating to deviations from predicted absorption kinetics [1],... 

Methods of controlling surface behavior are to 1. create polar and nonpolar regions in the molecule thus producing a hydrophilic-lipophilic balance in the molecule, 2. charge the... 

The II-A isotherms suggest an orientation that aligns the long axis of the polymer rod in the plane of the interface with the EO chains of the hydrophilic dendrons extended into the water layer and the hydrophobic dendrons pointed upward from the surface. The stability of the dendronized polymers likely arises from the balance between the polar and nonpolar regions exposed at the surface of the polymeric cylinder (Bo et al. 1999 Schluter and Rabe 2000). Ariga and colleagues (2004) constmcted a series of spider web dendritic amphiphiles that project hydrophilic Lys-Lys-Glu tripeptides and hydrophobic chains at each generational level (Fig. 11.42). 

Stacking of bases. The purines and pyrimidines of nucleic acids, as well as many other compounds with flat ring structures and containing both polar and nonpolar regions, are sparingly soluble in either water... 

A characteristic feature of molecules that form lyotropic liquid crystals is their surface activity. Because of the amphiphilic nature of the molecules, they orient upon contact with solvent molecules, giving rise to polar and nonpolar regions that are separated by the polar end groups. All structures known fit one of those made possible by the various curvatures of the interface between two liquid regions, with molecular size taken into consideration. It is therefore not surprising that the earlier treatment of the structure of lyotropic liquid crysals was unsuccessful since the molecules were regarded as stiff rods. 

There are drug molecules themselves that resemble surfactant molecules with polar and nonpolar regions exhibiting surface-active properties. These drugs can thus self-associate and fornr small aggregates or micelles. Examples of drugs that are surface active include Dexverapamil-HCI (Surakitbanharn etal., 1995), ibuprofen, and benzocaine. 

Special conditions are found in solutions of large cations and anions possessing a long unbranched hydrocarbon chain, e.g. CH3—(CH2) —CO M , CH3—(CH2) — SOf M , or CH3—(CH2) —N(CH3) X (with n > 7). Such compounds are known as amphiphiles, reflecting the presence of distinct polar and nonpolar regions in the... 

Fig. 10. An artist s visualization of a C, reversed phase in the presence of an aqueous mobile phase (I) and in the presence of butanol (H). The polar and nonpolar regions are denoted by the letters A and B, respectively. The possible conformations of the alkyl chain are represented by the sawtooth figures. Adapted from Hancock and Sparrow (198ld).

As polar derivatives of cholesterol, bile salts are highly effective detergents because they contain both polar and nonpolar regions. Bile salts are synthesized in the liver, stored and concentrated in the gall bladder, and then released into the small intestine. Bile salts, the major constituent of bile, solubilize dietary lipids (Section 22.1.1). Solubilization increases in the effective surface area of lipids with two consequences more surface area is exposed to the digestive action of lipases and lipids are more readily absorbed by the intestine. Bile salts are also the major breakdown products of cholesterol. 

Lipids are water-insoluble that are either hydrophobic (nonpolar) or amphipathic (polar and nonpolar regions). Lipids are in many ways the most diverse of the biological macromolecules, since they are something of a rag-tag bunch of leftovers. Lipids are pretty much everything in the cell that isn t very water soluble, and chemically they don t have a great deal in common with one another. The best known lipids are probably the fatty acids, so that is where we shall start. 

Bile Salts. Bile salts are polar derivatives of cholesterol. These compounds are highly effective detergents because they contain both polar and nonpolar regions. Bile salts are synthesized in the liver, stored and concentrated in the... 

Bile salts are the major component of bile and are very efficient detergents when conjugated to amino acids because of the presence of both polar and nonpolar regions, aiding in fat digestion. 

Bile salts are effective detergents because they contain both polar and nonpolar regions. They have several hydroxyl groups, all on one side of the ring system, and a polar side chain that allow interactions with water. The ring system itself is nonpolar and can interact with lipids or other nonpolar substances. Bile salts are planar, am-phipathic molecules, in contrast with such detergents as sodium dodecyl sulfate (text, p. 84), which are linear. 

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