Amino acid possessing functional groups

All amino acids possess at least two weakly acidic functional groups, R—and R—COOH. Many also possess additional weakly acidic functional groups such as —OH, —SH, guanidino, or imidazole groups. 

Figure 1.6 The ionizable amino acids possess some of the most important side-chain functional groups for bioconjugate applications. The C- and N-terminal of each polypeptide chain also is included in this group.

The amino acid residues of the apoflavoproteins (Scheme 2, (7) to (4)) involved in the covalent binding to the 8a-position of the prosthetic group possess functional groups which are ionizable in the pH range 6-10 as free molecules. These pK... 

Which two functional groups do amino acids possess ... 

Amino Acids Possessing Additional Actual or Potential Functional Groups... 

This chapter is concerned with the synthesis of those phosphonic and phosphinic acids which, with certain exceptions, do not possess functional groups as part of the carbon moieties of the acids those exceptions consist essentially of common functional groups attached to an aromatic ring. A consideration of the synthesis of those acids which possess the common functional groups such as hydroxyl, 0x0, or amino, is deferred to Chapters 3 and 4, whilst syntheses and properties of sulphur- and selenium-containing acids are described in Chapter 5. The reactions of phosphonic and phosphinic acids, many of which lead, of course, of new acids and are therefore often of value in synthesis, are dealt with in Chapter 6. 

Amino acids possess a dipolar nature. They are amphoteric, since they have both acidic and basic functional groups. Dipolar ions are often referred as zwitterions. In certain pH ranges, the amino acids exist predominantly as zwitterions, with a net charge of zero. 

The first asymmetric direct intermolecular aldol reaction catalyzed by L-proline was disclosed by List, Lemer, and Barbas III in 2000 [5]. Other amino acids possessing secondary amine groups were also screened but at best exhibited the same activity [14]. Both functional groups present on an amino acid are essential for good catalytic activity. Additionally, enantioselectivity is dependent on the distance between the amino and carboxylic groups, with (3-amino acids exhibiting lower enantioselectiv-ities [8f, 15]. 

Amino acids possess two functional groups able to participate in complexation. Appropriate design of the host molecule can lead to a particular host containing two binding sites specific for amino and carboxylic groups. 

Their name indicates that amino acids possess two characteristic functional groups the amino group, —NHj, and the carboxyl group, —COOH. All amino acids that occur as components of proteins have their amino group in a-position to the carboxyl group. A list of the 20 amino acids found regularly in proteins is presented in Table IV. They have trivial names which are abbreviated to the first three letters, with a few exceptions. 

The chemical properties of peptides and proteins are most easily considered in terms of the chemistry of their component functional groups. That is, they possess reactive amino and carboxyl termini and they display reactions characteristic of the chemistry of the R groups of their component amino acids. These reactions are familiar to us from Chapter 4 and from the study of organic chemistry and need not be repeated here. 

It is not only the activity that can be altered by incorporation of noncoded amino acids. Introduction of structures possessing certain chemical functions leads to the possibility of highly regioselective modification of enzymes. For example, selective enzymatic modification of cystein residues with compounds containing azide groups has led to the preparation of enzymes that could be selectively immobilized using click chemistry methods [99]. 

The cell must possess the machinery necessary to translate information accurately and efficiently from the nucleotide sequence of an mRNA into the sequence of amino acids of the corresponding specific protein. Clarification of our understanding of this process, which is termed translation, awaited deciphering of the genetic code. It was realized early that mRNA molecules themselves have no affinity for amino acids and, therefore, that the translation of the information in the mRNA nucleotide sequence into the amino acid sequence of a protein requires an intermediate adapter molecule. This adapter molecule must recognize a specific nucleotide sequence on the one hand as well as a specific amino acid on the other. With such an adapter molecule, the cell can direct a specific amino acid into the proper sequential position of a protein during its synthesis as dictated by the nucleotide sequence of the specific mRNA. In fact, the functional groups of the amino acids do not themselves actually come into contact with the mRNA template. 

The chloro group of 6 is now highly activated toward nucleophilic aromatic substitution, facilitating reaction with phenoxide. Subsequent catalytic reduction in the presence of LiOH produces amino acid 7. Next, treatment with butanol and sulfuric acid not only forms the butyl ester but monoalkylates the amino function. Saponification of the ester group leads to bumetanide (8), a diuretic agent possessing 40-fold greater activity in healthy adults than furosemide. ... 

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