Amino acids listed

FIGURE 27 1 Electro static potential maps of the 20 common amino acids listed in Table 27 1 Each ammo acid is oriented so that Its side chain is in the upper left corner The side chains affect the shape and properties of the ammo acids... 

The side chains of the 20 different amino acids listed in Panel 1.1 (pp. 6-7) have very different chemical properties and are utilized for a wide variety of biological functions. However, their chemical versatility is not unlimited, and for some functions metal atoms are more suitable and more efficient. Electron-transfer reactions are an important example. Fortunately the side chains of histidine, cysteine, aspartic acid, and glutamic acid are excellent metal ligands, and a fairly large number of proteins have recruited metal atoms as intrinsic parts of their structures among the frequently used metals are iron, zinc, magnesium, and calcium. Several metallo proteins are discussed in detail in later chapters and it suffices here to mention briefly a few examples of iron and zinc proteins. 

Proteins differ from the other polymers we have discussed in that they may contain up to 20 different monomer units. This means that there are a huge number of possible proteins. Using the amino acids listed in Table 23.3, we could make... 

Of the 20 amino acids the human body uses to build proteins, the adult body is able to produce 12 of them in amounts sufficient for its needs—it produces these amino acids from carbohydrates and fatty acids. The remaining 8, listed in Table 13.6, must be obtained from food. Because the body needs these eight amino acids but cannot synthesize them, they are called essential amino acids, in the sense that it is essential we get adequate amounts of them from our food. To support rapid growth, infants and children require, in addition to the eight amino acids listed for adults in Table 13.6, large amounts of arginine and histidine, which can be obtained only from the diet. Infants and juveniles therefore have a total of 10 essential amino acids. (The term essential is unfortunate because, in truth, all 20 amino acids are vital to our good health.)... 

Dr. Swain Yes, the amino acids listed as unknown from the Marcellus Formation are not among the common protein amino acids. It is suggested they may be aminobutyric acids, but this has not been verified. 

The 20 amino acids listed in Table 27.1 are biosynthesized by a number of different pathways, and we will touch on only a few of them in an introductory way. We will examine the biosynthesis of glutamic acid first because it illustrates a biochemical process analogous to a reaction we discussed earlier in the context of amine synthesis, reductive animation (Section 22.10). 

Several of the amino acids listed in Table 27.1 bear side-chain functional groups, which must also be protected during peptide synthesis. In most cases, protecting groups are available that can be removed by hydrogenolysis. 

A group of 20 amino acids, listed in Table 27.1, regularly appears as the hydrolysis products of proteins. All are a-amino acids. 

The major constituent of proteins is an unbranched polypeptide chain consisting of L-a-amino acids linked by amide bonds between the a-carboxyl of one residue and the a-amino group of the next. Usually only the 20 amino acids listed in Table 1.1 are involved, although they may be covalently modified after biosynthesis of the polypeptide chain. The primary structure is defined by the... 

Figure 25-4 Part of amino-acid chromatogram obtained by the method of automatic amino-acid analysis from a hydrolyzed sample of the enzyme ribonuclease. The component amino acids listed are present in the ratio Asp Thr Ser Glu Pro Gly Ala = 15 10 15 12 4 3 12, as determined by peak intensity. The volume of effluent is a measure of the retention time of the amino acids on the column.

Exercise 25-25 Indicate the steps that would be necessary to attach each of the amino acids listed to the A/-terminus of a peptide chain. Assume that any side-chain functions in the peptide are suitably protected, but do not assume that the amino acids will couple with the peptide without suitable protection of their functional groups, a. lysine b. aspartic acid c. cystine d. serine... 

For small peptides, the amount of color increases with the size of the peptide. The presence of any of five amino acid residues (tyrosine, tryptophan, cysteine, histidine, and asparagine) in the peptide or protein backbone further enhance the amount of color produced, because they contribute additional reducing equivalents for further reduction of the phos-phomolybdic/phosphotungstic acid complex. With the exception of tyrosine and tryptophan, free amino acids will not produce a colored product with the Lowry reagent however, most dipeptides can be detected. In the absence of any of the five amino acids listed above, proteins containing proline residues have a lower... 

C is correct The solubilities of amino acids differ based upon the R group. Phenylalanine has a benzene R group and is the least polar amino acid listed. The carboxylic acid and amines on the other R groups increase solubility. You may have also memorized the four groups of amino acid side chains as either nonpolar, polar, acidic, or basic. Acidic, basic, and polar amino adds have greater water sohibility than nonpolar amino acids. 

Learn the names, structures, and abbreviations of the amino acids listed in Table 17.1. 

The other amino acids listed (b, c, e) have polar R groups, which will point toward the surface and hydrogen-bond with water, thus helping to solubilize the protein. 

Figure 4 Dehydratase (DH) consensus sequence of avermectin module 10 (inactive), module 9 (active), module 2, and erythromycin DH domains. Amino acids listed in the consensus line in capital letters are shared by all 4 DHs, and those in lower case are shared by 3 of the 4 regions. The underlined module 10 region was inserted into module 2 or the underlined module 9 region was inserted into module 2 for gene replacement experiments. The ( ) sequences are the conserved HxxxGxxxxP active domain.

When proteins are hydrolyzed with acid at high temperature, they are broken down to their constituent amino acids. Commonly, the amino acid cystine is found among them. But cystine is not included among the amino acids listed in the dictionary of codons. Why ... 

Several enzyme classes have been used to synthesize amino acids, listed below ... 

Databases are the essential resource for work in this area. They are the repositories of sequence information on a variety of organisms, induding the human genome, and databases in the public domain can all be acessed via the Internet. Sequences are stored in databases using the internationally agreed one-letter codes from nucleic acids and amino acids listed in Table 8-2. 

In the adult human, lysine is an essential amino acid. It cannot be synthesized de novo from non-protein sources. In the child, both arginine and lysine are essential since there is a need for more arginine than can be supplied by endogenous routes. The combination of trypsin and carboxypeptidase B seems to be a convenient evolutionary device to ensure an adequate supply of these amino acids from dietary protein. Similarly, the other essential amino acids listed in Table II are those most likely to arise from the combined action of pepsin and chymotrypsin followed by carboxypeptidase A. Hence, the overall proteolytic apparatus is apparently designed to meet the nutritional needs of man for essential amino acids. 

Although all of the amino acids listed in Table SO-1 are present in the proteins of the human body, not all of them need to be in the food. Experiments have been carried out which show that nine of the amino acids are essential to man. 1 hese nine essential amino acids are histidine, lysine, tryptophan, phenylalanine, leucine, isoleucine, threonine, methionine, and valine. The human body seems to be able to manufacture the others, which are called the non-essential amino acids. Some organisms that we usually consider to be simpler than man have greater powers than the human organism, in that they are able to manufacture all of the amino acids from inorganic constituents. The red bread mold, Neurospora, has this power. 

The amino acids listed below are prepared in similar manner by reaction of the proper organic halide with benzamidomalonic ester (p. 145). The halides used and the yields of dl-amino acid obtained are given in parentheses phenylalanine (benzyl chloride, 90%), aspartic acid (ethyl chloroacetate, 62%) and valine (isopropyl iodide, 71%). 

How many different polypeptides, each containing ten amino acids, can be made from the amino acids listed in Table 23.3 How many different polypeptides, each containing 100 amino acids, can be made ... 

Fig. 3. Map of Ri values of the amino acid standard solution separated on TLC microplates as described in Section 4.5. The numbers correspond to the amino acids listed in Table 2, and the dotted circles to the position of some amino acids commonly found in biological fluids which are not present in the standard solution.

C. Leucine but none of the other amino acids listed is a branched-chain amino acid. The muscle has a very active branched-chain amino acid metabolic pathway and uses that pathway to provide energy for its own use. The products of leucine metabolism are acetyl-CoA and acetoacetate, which are used in the tricarboxylic acid cycle. Acetoacetate is activated by succinyl-CoA and cleaved to two molecules of acetyl-CoA in the P-ketothiolase reaction. The other branched-chain amino acids, valine, and isoleucine, yield succinyl-CoA and acetyl-CoA as products of their catabolism. 

Using this (LI) preparation procedure, Stefanovic and Walker (SO) studied the effect of stationary phase-support ratio on the gas-chromatographic separation of trifluoroacetylamino acid butyl esters using ethylene glycol adipate polyester columns. They found that, for certain amino acids, the elution pattern was a function of the amount of liquid phase on the column packing. When 0.5% ethylene glycol adipate was used, sharp well-defined peaks were obtained and all the amino acids listed in Table 6 except cysteine and methionine were completely sepa-... 

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