Amino acids, simplest

Glycine is the simplest member of a large and very important class of compounds, the a-amino-carboxylic acids. TTiere are many different methods available for the synthesis of amino-acids, but glycine can be readily prepared by the action of an excess of ammonia on chloroacetic acid ... 

Amino acids are the main components of proteins. Approximately twenty amino acids are common constituents of proteins (1) and are called protein amino acids, or primary protein amino acids because they are found in proteins as they emerge from the ribosome in the translation process of protein synthesis (2), or natural amino acids. In 1820 the simplest amino acid, glycine, was isolated from gelatin (3) the most recendy isolated, of nutritional importance, is L-threonine which was found (4) in 1935 to be a growth factor of rats. The history of the discoveries of the amino acids has been reviewed... 

Protein Components. The simplest picture of the proteinaceous components is one of polypeptides, which are composed of a-amino acid residues. It is estimated that wool contains about 170 different types of polypeptides varying in molecular mass from below 10,000 to greater than 50,000 (34). Complete acid hydrolysis of wool yields 18 amino acids, the relative amounts of which vary considerably from one wool to another. Typical figures for two different samples of wool are given in Table 7. 

This carboxyborane can undergo an amine exchange reaction with Hquid ammonia (eq. 7) to yield the boron analogue of glycine, the simplest alpha-amino acid (13). There has been a great deal of work on the pharmacological activity of these amino acid analogues (14). 

The amino acids are usually divided into three different classes defined hy the chemical nature of the side chain. The first class comprises those with strictly hydrophobic side chains Ala (A), Val (V), Leu (L), He (1), Phe (F), Pro (P), and Met (M). The four charged residues, Asp (D), Glu (E), Lys (K), and Arg (R), form the second class. The third class comprises those with polar side chains Ser (S), Thr (T), Cys (C), Asn (N), Gin (Q), His (H), Tyr (Y), and Trp (W). The amino acid glycine (G), which has only a hydrogen atom as a side chain and so is the simplest of the 20 amino acids, has special properties and is usually considered either to form a fourth class or to belong to the first class. 

The simplest motif with a specific function consists of two a helices joined by a loop region. Two such motifs, each with its own characteristic geometry and amino acid sequence requirements, have been observed as parts of many protein structures (Figure 2.12). 

In this chapter we will discuss immunoglobulins of the IgG class, which is the major type of immunoglobulin in normal human serum, and which has the simplest structure. Each chain of an IgG molecule is divided into domains of about 110 amino acid residues. The light chains have two such domains, and the heavy chains have four. 

Glycine is the simplest anino acid and the only one in Table 27.1 that is achiral. The a-carbon atom is a chirality center in all the others. Configurations in amino acids are normally specified by the d, l notational system. All the chiral amino acids obtained from proteins have the l configuration at their- a-carbon atom, meaning that the amine group is at the left when a Fischer projection is arianged so the carboxyl group is at the top. 

Proteins are complex molecules that give cells structure and act as both enzymes and motors within cells. Proteins are long strings of amino acids folded in specific three-dimensional formations. There are twenty different animo acids in our bodies. DNA, the genetic material located in the cell nucleus, carries information for the order of the amino acids in each protein. Indeed, in the simplest sense, a gene is the... 

It has been proposed that if ammonia, methane, and oxygen gas are combined at 25°C in their standard states, glycine, the simplest of all amino acids, can be formed. 

As described in Section 2.3.2, vinylaziridines are versatile intermediates for the stereoselective synthesis of (E)-alkene dipeptide isosteres. One of the simplest methods for the synthesis of alkene isosteres such as 242 and 243 via aziridine derivatives of type 240 and 241 (Scheme 2.59) involves the use of chiral anti- and syn-amino alcohols 238 and 239, synthesizable in turn from various chiral amino aldehydes 237. However, when a chiral N-protected amino aldehyde derived from a natural ot-amino acid is treated with an organometallic reagent such as vinylmag-nesium bromide, a mixture of anti- and syn-amino alcohols 238 and 239 is always obtained. Highly stereoselective syntheses of either anti- or syn-amino alcohols 238 or 239, and hence 2,3-trans- or 2,3-as-3-alkyl-2-vinylaziridines 240 or 241, from readily available amino aldehydes 237 had thus hitherto been difficult. Ibuka and coworkers overcame this difficulty by developing an extremely useful epimerization of vinylaziridines. Palladium(0)-catalyzed reactions of 2,3-trons-2-vinylaziri-dines 240 afforded the thermodynamically more stable 2,3-cis isomers 241 predominantly over 240 (241 240 >94 6) through 7i-allylpalladium intermediates, in accordance with ab initio calculations [29]. This epimerization allowed a highly stereoselective synthesis of (E) -alkene dipeptide isosteres 243 with the desired L,L-... 

Write the complete Lewis structure for each of the following compounds (a) formaldehyde, HCHO, which as its aqueous solution formalin is used to preserve biological specimens (b) methanol, CH3OH, the toxic compound also called wood alcohol (c) glycine, H2C(NH2)COOH, the simplest of the amino acids, the building blocks of proteins. 

Amino acids are the building blocks of proteins, which have long chainlike molecules. They are oxidized in the body to urea, carbon dioxide, and liquid water. Is this reaction a source of heat for the body Use the information in Appendix 2A to predict the standard enthalpy of reaction for the oxidation of the simplest amino acid, glycine (NH2CH2COOH), a solid, to solid urea (H2NCONH2), carbon dioxide gas, and liquid water ... 

We know, as the measured values of dp and dN (from the DIFF in Section 2.4) imply, that isofractionation takes place within the organism. To include fractionation in the model, the fractionating steps must be made explicit. The simplest arrangement, consistent with observation, is as labeled in Fig. 11.2. That is, a fractionation of +2.5%o from the amino acid pool to collagen suf-... 

Acyl groups are common in bacterial polysaccharides. The parent acids are fatty acids, hydroxy acids, and amino acids. The simplest acid, formic acid, has only been found as the amide. The occurrence of O-formyl groups had been reported, but proved to be incorrect. A-Formyl groups have been found in different polysaccharides for example, in the 0-specific side-chains of the LPS from Yersinia enlerocolitica 0 9, which are composed of 4,6-dideoxy-4-formamido-D-mannopyranosyl residues. The formyl group can assume two main conformations, s-cis (41) and s-trans (42), which are... 

Twenty different amino acids are used to build proteins in living cells. The simplest is glycine, where R = H. In each of the 19 amino acids other than glycine, the side chain begins with a carbon atom. The side chains in naturally occurring amino acids are shown in Figure 13-32. 

Figure 1.1 The chemical structures of the main neurotransmitters. The relatively simple structure of acetylcholine, the monoamines and the amino acids contrasts with that of the peptides, the simplest of which are the enkephalins which consists of five amino acids substance P has eleven...

Glycine is the simplest of all amino acids. It is involved in many metabolic pathways, is an essential component of proteins, and is found throughout the brain. A neurotransmitter role for glycine was first identified in the spinal cord, where it was found to be differentially distributed between dorsal and ventral regions and shown to cause hyperpolarisation of motoneurons (Werman et al. 1967). This inhibitory action of glycine is distinct from its... 

Treatment of the simplest amino acid glycine, with r7,y-[Pt(NI I3)2(I I20)2]21 in aqueous solution affords cw-[Pt(NH3)2(0-glyH)(H20)]2+ (87), in which the glycine is coordinated to the metal center via the 0-atom only.262 The product subsequently converts to the thermodynamically... 

The interesting list of molecules in Table 3.3 includes one amino acid in the group of molecules with more than 10 atoms it is the simplest proteinogenic amino acid, glycine. 

However, the amino acids were not necessarily formed in the gas phase. John Oro, one of the pioneers in prebiotic chemistry, carried out syntheses in the liquid phase by reacting HCN, NH3 and H2O at 353 K. The results were confirmed by Lowe et al. (1963) and developed further ten years later, Jim Ferris took them up and did considerable further work (Ferris et al., 1973, 1974). In all these simulation experiments, the simplest amino acids (glycine, alanine and in small amounts aspartic acid and a-aminobutyric acid) are, as expected, the main products the yields of glycine are around 1%, those of the other amino acids much lower. 

The simplest amino acid, glycine, is almost always the one formed in highest yield in prebiotic syntheses. Thus, the first polycondensation experiments were carried out with glycine. Akabori (1955) and Hanabusa and Akabori (1959) reacted aminoace-tonitrile with kaolin at 403 108 K. The starting material is readily formed as follows ... 

Detection and quantification of protein by measuring absorbency at 280 nm is perhaps the simplest such method. This approach is based on the fact that the side chains of the amino acids tyrosine and tryptophan absorb at this wavelength. The method is popular, as it is fast, easy to perform and is non-destructive to the sample. However, it is a relatively insensitive technique, and identical concentrations of different proteins will yield different absorbance values if their content of tyrosine and tryptophan vary to any significant extent. Hence, this method is rarely used to determine the protein concentration of the final product, but it is routinely used during downstream processing to detect protein elution off chromatographic columns, and hence track the purification process. 

Probably the most striking difference between neuropeptides and conventional neurotransmitters is in their biosynthesis (Fig. 18-2). Neuropeptides are derived from larger, inactive precursors that are generally at least 90 amino acid residues in length [2-4]. The simplest example is prolactin, a pituitary product. The signal sequence for... 

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