R-groups hydrophobic

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-... 

Primary structures are stabilized by covalent peptide bonds. Higher orders of structure are stabilized by weak forces—multiple hydrogen bonds, salt (electrostatic) bonds, and association of hydrophobic R groups. 

Figure 2. Foam drainage and water loss from the bubble wall concentrate is diluted into a premix, and the foam is generated from the premix. When foam is generated, hydrophobic R groups become part of the bubble wall (X = width of bubble wall). X decreases as water drains downward under the influence of gravity. The polymer strands prevent narrowing of bubble wall, decreasing drainage time and stabilizing the foam.

How would hydrophobic R groups affect the three-dimensional structure of a protein ... 

Hydrophobic R groups would force a protein to align itself away from water. 

Amino acids with nonpolar (hydrophobic) R-groups are generally found in the interior of proteins that function in an aqueous environment, and on the surface of proteins (such as membrane proteins) that interact with lipids. Amino acids with polar side chains are gener ally found on the outside of proteins that function in an aqueous environment, and in the interior of membrane-associated proteins. 

Likewise, greater retention time for the nonpolar support phase increases for Mm(R-acac)3 as more hydrophobic R groups replace CH3 of acetylacetonate (acac-) and if S replaces the O donors in thioacetylacetonates for M111 = Crm, Co111, Ru111, and lanthanide(III) ions.37,38... 

As a polypeptide folds into its unique three dimensional form, most hydrophobic R groups (yellow-spheres) become buried in the interior away from water. Hydrophilic groups usually occur on the surface. 

Zwitterionic and amphoteric surfactants contribute to the overall generation of foam, foam stability and foam quantity. Regardless of the type of amphoteric, a generalization can be made concerning the hydrophobic R group The total number of carbon atoms in the R group has a profound effect upon performance. 

Globular proteins have more amino acids with polar or ionic side chains than the water-insoluble fibrous proteins. An enzyme or other globular protein that carries out its function mainly in the aqueous medium of the cell will adopt a structure in which the nonpolar, hydrophobic R groups point in toward the center and the polar or ionic R groups point out toward the water. 

Hydrophobic attraction. Retention of RCO2H analytes becomes stronger as the size of the hydrophobic R group... 

This effect, not encountered in other lactams (e.g., CL and 2-pyrrolidone) or in lactones, has been attributed to the large hydrophobic R group that inhibits the contact, or intimate ion-pair formation, between the counter ion (IC or Me4N ) and the lactam N anion. Such phenomenon occurs in polar DMSO solvent, where the 3-butyl-3-methyl-substituted lactam may probably exist as an almost free ion having enhanced reactivity. Indeed, subsequent studies conducted in tetrahydrofiiran (THF) revealed, as expected, a deaease in the polymerization rate with the size of substituents. 

A tertiary structure is stabilized by interactions that push amino acids with hydrophobic R groups to the center and pull amino acids with hydrophilic R groups to the surface, and by interactions between amino acids with R groups that form hydrogen bonds, disulfide bonds, and salt bridges. 

Two amino acids with hydrophobic R groups move toward the inside of the folded protein. 

---