Polar side groups

Both side groups and carbon-carbon double bonds can be incorporated into the polymer structure to produce highly resilient rubbers. Two typical examples are polyisoprene and polychloroprene rubbers. On the other hand, the incorporation of polar side groups into the rubber structure imparts a dipolar nature which provides oil resistance to these rubbers. Oil resistance is not found in rubber containing only carbon and hydrogen atoms (e.g. natural rubber). Increasing the number of polar substituents in the rubber usually increases density, reduces gas permeability, increases oil resistance and gives poorer low-temperature properties. 

The hydrophilic polar side group on glutamic acid is capable of forming hydrogen bonds with water and thus helps to keep normal hemoglobin dispersed within the red blood cells. 

Hydrophilic attractions between a protein and an aqueous medium, such as cytoplasm or blood, also help maintain tertiary structure. In a protein dissolved in an aqueous medium, the polypeptide chain is folded so that nonpolar side groups are on the inside of the molecule and polar side groups are on the outside, where they interact with the water. 

A number of the amino acids in Table 1 have polar side groups and hence the potential of becoming tridentate. As will be seen later it is these third sites which become important in protein binding of metal ions. 

In Fig. 30, a three-dimensional model is presented in which only the organic phases are shown. Hexagonal plates of MM alternate with pleated sheets of CP. The hydrophobic sides of MM are facing each other and encase the mineral phase. The relationship between hydrophobic bonding and accessible surface area in proteins, and the effect of polar and non-polar side groups on free energy values has recently been discussed246. For informations on hydrophobicity in protein systems see Refs.247-252. ... 

Chromotropism in the presence of an electric field, electrochromism, has been observed for just one polysilane, the copolymer (CF3CH2CH2SiMe) -co-(ftPrSiMe)m, n m = 45 55.89 The UV band for this polymer is intensified by 50% and shifted from 294 to 299 nm, in an electric field of 10s v/m. The changes are reversible when the field is removed. Other polysilanes with polar side groups might also show electrochromic behavior, but none have been studied. 

Polar side groups are hydrophilic and will turn to face an aqueous solution such as cytosol. Nonpolar side groups are hydrophobic and will turn away from an aqueous solution. These characteristics affect a proteiiTs tertiary structure. 

Scheme 6.7 Shape-persistent macrocycle 56 with an adaptable arrangement of the polar and non-polar side-groups by the intermole-cular acetylene coupling of the corresponding...

Meng, X., Natansohn, A., Barrett, C., Rochon, P. (1996). Azo polymers for reversible optical storage. 10. Cooperative motion of polar side groups in amorphous polymers. Macromolecules 29, 946-952. 

Hydration of polar side groups and peptide bonds. This must provide a large term in AG, including enthalpic and entropic contributions. It cannot be separated from the interactions mentioned in items 1 and 2. 

Protein tertiary structure results from hydrophobic interactions between nonpolar side groups and hydrogen bonds between polar side groups that stabilize folding of the secondary structure into a compact overall arrangement, or conformation. 

Problem 20.40. Which has the more polar side group, alanine or serine ... 

Napper [175] was the first to study the adsorphon of nanopartides in polymers and since then, different types of polymers Hke vinyl polymers with polar side groups such as poly(vinyl)pyrrolidone (PVP) and poly (vinyl) alcohol (PVA) have been applied [69, 176-179]. 

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