Polar basic amino acids

If the substitution of an amino acid in the protein affects an interaction essential to functional structure or the binding of a substrate, the resulting protein could be less effective or nonfunctional. In this example, glycine, a nonpolar amino acid, replaces arginine, a polar basic amino acid. The shape of this protein is likely to change because there will be disruptions of interactions such as salt bridges and hydrophilic interactions. 

What about tertiary structure Why does any protein adopt the shape it does The forces that determine the tertiary structure of a protein are the same forces that act on ail molecules, regardless of size, to provide maximum stability. Particularly important are the hydrophilic (water-loving Section 2.13) interactions of the polar side chains on acidic or basic amino acids. Those acidic or basic amino acids with charged side chains tend to congregate on the exterior of the protein, where they can be solvated by water. Those amino acids with neutral, nonpolar side chains tend to congregate on the hydrocarbon-like interior of a protein molecule, away from the aqueous medium. 

Examination of the antigenic sites of lysozyme reveals tFat they are very rich In basic amino acids. This was also seen In Mb, but we caution against premature generalizations. Obviously, Interactions with antibody are predominantly polar In nature (as... 

Monotrifluoroacetylated diaminopyrazole was first reacted with the free Kemp s triacid to produce the imide, followed by N-Boc protection and amide-coupling with a m-substituted aniline derivative. Final Boc-deprotection occurred on the chromatography column leading directly to the new receptor modules. The recognition site X was chosen to be ethyl as a neutral reference, acetyl for polar side-chains, nitro for electron-rich aromatic residues and carboxylate for basic amino acids (Figure 2.4.4). 

The best substrates for ophidian L-amino acid oxidases are aromatic or, most generally, hydrophobic amino acids, polar and basic amino acids being deami-nated at much lower rates Glu, Asp, and Pro are not oxidized by L-amino add oxidase. L-Amino add oxidase is also active on ring-substituted aromatic amino acids, as well as on seleno cysteinyl derivatives. The substrate specificity depends on the source of the enzyme (e.g. Ophiophagus hannah L-amino acid oxidase also oxidizes Lys and Om) and on the pH. The of the reaction of Crotalus adaman-... 

Arginine is an essential amino acid found in proteins and is one of three amino acids categorized as basic amino acids. The basic amino acids are strongly polar, and ... 

The basic amino acids are strongly polar, and as a consequence, they are usually found on the exterior surfaces of proteins, where they can be hydrated by the surrounding aqueous environment. 

Aromatic Amino Acids (Strong absorption of light in near UV) (Figure 5.6) Phenylalanine, Tyrosine, Tryptophan Basic Amino Acids (Strongly polar, usually on exterior of proteins) (Figure... 

The adsorption of various amino acids from aqueous solutions using MCM-41-type mesoporous molecular sieves is discussed on the basis of their adsorption isotherms. The amounts adsorbed strongly depend on the pH and the nature of the individual amino acid Amino acids with acidic side chains are hardly adsorbed, whereas basic amino acids show very high affinities to the mesoporous adsorbent. The uptake of amino acids with non-polar side chains increases with the chain length. The adsorption complex is proposed to consist of the cationic form of the amino acid attached to the negatively charged silica surface. 

Figure 24.18 Those labeled basic amino acids, which have basic side groups that are protonated at pH 7 Figure 24.25 The long hydrocarbon chains, which are nonpolar Figure 24.27 The polar parts of the phospholipids seek to interact with water whereas the nonpolar parts seek to interact with other nonpolar substances and to avoid water.

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