Structures of Amino Acids

The structures of amino acids incorporated into polypeptides and proteins may be characterized by a pair of dihedral angles involving the so-called a carbon for each amino acid. 

Substantial progress can be expected in the near future concerning the structure of amino acid transporters, their functional dissection, and their evolutionary filiation. 

Marsh, R. E., and J. Donohue. 1967. Crystal Structures of Amino Acids and Peptides. Adv. Prot. Chem. 22, 235-256. 

The aims of this contribution are to (i) consider the theoretical principles underlying the use of compound-specific stable isotope analysis in archaeology (ii) consider the practical aspects of undertaking compound-specific stable isotope analyses and (iii) demonstrate the value of linking the structures of amino acids, fatty acids and/or sterols, to their compound-specific stable isotope values to achieve new insights into variations in metabolism and environment in order to enhance archaeological interpretations. 

Figure 6.10 Structures of amino acids having overall net charges at pH 7.0. In proteins, the charges associated with the a-amino and a-carboxyl groups in all but the terminal amino acids are not present, as these groups are directly involved in the formation of peptide bonds...

Chemical strengthening, 13 498-499 Chemical structures, of amino acids,... 

Cation-TT interactions play a crucial role in molecular recognition. For example, Na /K cation interactions with aromatic rings of some amino acids are implicated in the biological functions of specific enzymes and in the selectivity of Na" /K channels. " The same factors are responsible of the relative stability of the charge-solvated vs. zwitterionic structure of amino acids. " ... 

Infrared Analysis of the Structure of Amino Acids, Polypeptides, and Proteins... 

Cyclosporine A itself and a number of other cyclosporines have been completely synthesized. Many stmctural analogs have also been synthesized, and a few patterns have been discovered in terms of their structure and activity. It is known that the activity of the dmg is determined by the entire cyclic stmcture, and not by its separate fragments. Likewise, it is also clear, that the structure of amino acids at position 1 is an important factor of... 

Another derivatization approach is reduction of the hydroperoxide, followed by structural characterization of the corresponding alcohol, which is usually easier to handle. Thus, the structure of amino acid hydroperoxides can be characterized more easily if, after having ascertained the hydroperoxide nature of the compound, it is reduced to the alcohol with NaBH4. The structure of three valine hydroperoxides obtained on y-radiation of bovine serum albumin, a tripeptide (31) or valine (34) was elucidated after reduction, hydrolysis (if necessary), chromatographic separation, and application of the usual MS and NMR methods on the individual hydroxy derivatives of valine. ... 

After receiving his Ph.D., Dr. French spent two years, 1942 to 1944, as a post-doctorate fellow in the laboratories of Professors J. D. Edsall and E. J. Cohn at Harvard Medical School. During this period, French worked in the area of amino acids and proteins, and he became especially interested in relating the structure of amino acids and proteins to chemical reactivity. With Dr. Edsall, he published an excellent review on the reactions of formaldehyde with amino acids and proteins. In this stage of his career, his interest was aroused in proteins that possess enzymic activity. In later years, much of his research was devoted to enzymes and their mode of action, and to the molecular mechanisms and theoretical aspects of enzyme action. 

Scheme 18 Structures of Amino Acids Containing Benzophenone Derivatives1150"1531...

Correlations between the structures of amino acids and peptides and their I3C chemical shifts are of general interest for bio-, enzyme- and peptide chemists, since these compounds occur in all cells of living organisms. 

Side-chain group (a) Generalized structure of amino acid... 

I n the previous three chapters we described the structures of amino acids and proteins, and in two cases we examined how these structures relate to their function. Some of the methods for structure determination were also discussed (e.g., sequence analysis in chapter 3 and x-ray diffraction in chapter 4). To analyze the structure of a protein we must isolate it from the complex mixture in which it exists in whole cells. The primary object of this chapter is to acquaint you with techniques used for protein purification. Because these procedures are often used for protein characterization as well, they will add to your repertoire of methods for protein characterization. 

Name and draw the structures of amino acids that fit the following descriptions ... 

Infrared analysis of the structure of amino acids, polypeptides and proteins. Advanc. Protein. Chem. 7, 291—318 (1952). 

Fig. 17 General structures of amino acid derivatives linked with phosphates and exhibiting potential biological activity...

Proteins consist of a primary structure of amino acid residues connected in a definite sequence by peptide linkages to form polypeptide chains ... 

We saw in Section 4.6.1 the use of zwitterionic hosts for anions in which the counter-cation is non-speciflcally bound on the outside of the molecule. We now turn to zwitterionic guests where the guest has both cationic and anionic parts. We have already described in Section 5.1.1 the zwitterionic structure of amino acids and amino acid binding has been a major part of the interest in the construction of hosts for zwitterions. An excellent example is compound 4.30 (Section 4.5) which is... 

The structures of amino acids can also contain other functional groups besides the amine and carboxylic acid groups (Table 1.1). Methionine, for example, contains a sulphide group, whilst serine has a primary alcohol group. 

All solid amino acids exist as dipolar ions known as zwitterions (Figure 1.2(a)). In aqueous solution the structure of amino acids are dependent on the pH of the solution (Figure 1.2(b)). The pH at which an aqueous solution of an amino acid is electrically neutral is known as the isoelectric point (pi) of the amino acid (Table 1.1). Isoelectric point values vary with temperature. They are used in the design of electrophoretic and chromatographic analytical methods for amino acids. 

Figure 1.2 (a) The general structural formula of the zwitterions of amino acids, (b) The structures of amino acids in acidic and basic aqueous solutions... 

PROPERTIES OF AMINO ACIDS 4.2.1 Structures of Amino Acids... 

Optical chirality of molecules is a characteristic measure of stereo-chemical property of biological, pharmaceutical, and metal coordination compounds. Choral structures of amino acids, proteins, DNAs, and various drugs in solutions have been determined from the measurement of circular dichroism (CD). However, small amount of molecules at the liquid-liquid interfaces has never been measured before CLM/CD method [19] and SHG/CD method have been reported [20],... 

The preceding results indicated that subtle geometrical structures of amino acids and peptides were imprinted in Ti02-gel matrices. It is conceivable that the imprinting effect is not restricted to geometrical differentiations. 

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