Acidic side chains, amino acid

X-Amino acids ate ampholytic compounds. The chemical reactions of amino acids can be classified according to their carboxyl, amino, and side-chain groups. Most of the reactions have been well known for a long time the details of these reactions have been reviewed (77). 

A rather more complex amino alcohol side chain is accessible by a variation of the Mannich reaction. Taking advantage of the acidic proton in acetylenes, propargyl acetate (62) is condensed with formaldehyde and dimethylamine to give the acetylated amino... 

Figure 3.1 Amino add side-chain groups involved in binding NAD at the active site of an enzyme. The enzyme is glyceraldehyde dehydrogenase. More than 20 amino acids, the position of which in the primary structure is indicated by the number, counting from the N-terminal amino acid, are involved in the binding. This emphasises the complexity of the binding that is responsible for the specificity of the enzyme for NAD (depicted in bold). The molecular structure of nicotinamide adenine dinucleotide (NAD ) provided in Appendix 3.3.

Having an increased or elevated reactivity. This term has been used in reference to the relative activity of amino acyl residues at the active sites of enzyme. The immediate environment (Le., the microenvironment) may allow simple reagents to react faster with the amino acid than would normally be expected. Thus, in labeling of proteins with active site-directed reagents, an investigator should always consider the basis of increased reactivity Is it due to facilitation of the reaction by increased affinity (Le., affinity labeling), or is it due to increased activity of the amino acyl side chain (e.g., perhaps increased nucleophilicity due to the microenvironment). 

An A -methyl-amino-oxy amino acid has also been incorporated into peptides using standard SPPS procedures. Reaction of these peptides with native reducing sugars yields neoglycopeptides via a chemoselective reaction with the amino-oxy side chains, maintaining the linked sugars in their cyclic conformations and... 

X Sugars, amino add side chains, ribonucleic acid... 

Figure 1. Types of antigenic determinants. An assembled epitope is composed of amino acid side chains (1,2, and 3) that are well separated in the linear sequence of the protein but are brought together during folding of the protein. A segmental epitope is composed of amino add side chains (A, B, and C) that are contiguous both in the linear sequence of the protein and on the surface of the protein in its folded form.

The ferrocenylbisphosphines 8f—h bearing the amino pendant side chain are unique ligands that effect the rhodium-catalyzed asymmetric hydrogenation of tetrasubstituted olefms 57 (Scheme 2-43) [61]. Thus, the hydrogenation of a-aryl-acrylic acid 57a in the presence of a cationic rhodium catalyst coordinated with 8g gives a quantitative yield of carboxylic acid 58a with 98.4% ee. Other tetra-... 

Phase I reactions of chlorpromazine that have been reported include the following oxidative N-demethylation to yield the corresponding primary and secondary amines (368-371) aromatic hydroxylation to yield phenols (369-376) N -oxidation to yield the N-oxide (371, 372, 376, 377) S-oxidation to yield sulfoxide (369-373) and sulfone (378) oxidative deamination of the amino propyl side-chain (probably preceded by iV-demethyl-ation) to yield the carboxylic acid (371,379) ... 

Aromatic amino and side chain ketone groups are annulated by heating in a base. An AT-protected amino acid reacts with a 2-aminobenzophenone (review... 

More recently an oil continuous microemulsion technique has been described, which allows the study of specific interactions between amino add side chains and metal ions. Both the metal ion and amino acid are microencapsulated as aqueous droplets in a dispersed phase. The technique is of particular relevance to metalloprotein and metal-membrane interactions where the local dielectric constant can be considerably less than that of bulk water. 

In the particular case of alcohol dehydrogenase, outlined in Section 15.3, the combination of temperature studies with solvent perturbation will separate the neutral amino acids from the cationic ones, provided the group is ejqiosed to the solvent. Thus, by combining the knowledge of pK and the heat of ionization for a given amino add side chain with a solvent perturbation method, a fairly accurate identification of an amino acid can be achieved. 

Assign charges to amino add side chains. The active site residue protonation state is important and can have a significant effect on binding affinity. The protonation states of amino acid residues such as His, Lys, Glu, and Asp are usually based on their pX values but can be influenced by neighboring donor-acceptor groups. 

P. E. Smith and B. M. Pettitt. Amino acid side-chain populations in aqueous and saline solution Bis(penicillamine) enkephalin. Biopolymers, 32 1623-1629,... 

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