Amino acids chemical structure

Arginine, 2D biosynthesis, 435 catabolism, 431 134 chemical structure, 20 plasma concentration, 465 Argininosuccinate lyase, 439 Acgininosuccinate synthase, 439 Aromatic amino acids, chemical structure, 19 Arsenate, 840 Artenosclcrosis, 357 Arteriovenous differences, 19 199 Artery, physiology, 359 Ascoitale... 

Wadhwani P, Tremouilhac P, Strandberg E, Afonin S, Grage S, Ieronimo M, Berditsch M, Ulrich AS (2007) Using fluorinated amino acids for structure analysis of membrane-active peptides by solid-state 19F-NMR. In Soloshonok V, Mikami K, Yamazaki T, Welch JT, Honek J (eds) Current fluoroorganic chemistry (ACS symposium series). American Chemical Society, Washington, pp 431 146... 

The physical and chemical properties of the measurement site greatly influence accuracy of noninvasive clinical measurements. Noteworthy physical parameters include thickness, scattering properties, and temperature of the tissue at the measurement site. Chemical issues center on the molecular makeup of the tissue (water, protein, fats, amino acids, glycolytic structures, etc.) and the heterogeneous distribution of these chemical components throughout the measurement site. 

Sun, S.-Y., Pratt, E. A. and Ho, C. (1996) 19F-labeled amino acids as structural and dynamic probes in membrane-associated proteins, in Biomedical Frontiers of Fluorine Chemistry (eds. I. Ojima, J. R. McCarthy and J. T. Welch), American Chemical Society, Washington, D.C., pp. 

Nitrosamines are derived from amines, and like aU Af-nitroso compounds, they have the N-N=0 functional group. They can be classified as volatile and nonvolatile. Volatile nitrosamines, in contrast to nonvolatile nitrosamines, can be removed from the matrix by distillation techniques and can be analyzed by gas chromatography (GC) without prior chemical derivatization. Alkyl and cyclic nitrosamines, which are volatile, have been intensively studied. The most commonly encountered nonvolatile nitrosamines are aryl compounds, hydroxylated compounds, and V-nitrosated amino acids. The structures of several nitrosamines are shown in Figure 12.1. 

The isomeric acromelic acids A and B display a powerful neuroexcita-tory action and are structurally related to the anthelmintic kainic acid (406,407) and domoic acid (408), the known principles from the marine red algae Digenea simplex and Chondria armata, respectively. Both of the latter amino acids, the structures of which were determined by chemical and X-ray studies, attracted considerable interest as well because of their... 

The sequences represented in the chemical linkages of nucleotide/amino acid/glycose structures are 2D drawings. The nucleotide/amino acid sequences in character format (without index, e.g. fasta format) can be converted into the 2D structures with ISIS Draw (Figure 14.9), which can be downloaded from MDL Information System at http //www.mdli.com/download/isisdraw.html... 

From the young pea seedlings of Pisum sativum L. var. Rondo there was isolated another pyrimidine amino acid, the structure of which was initially proposed [429] as L- -(5-uracilyl)alanine (LXXVIIIa). However, its physical constants by no means agree with those of the authentic -(5-uracilyl)alanine unequivocally synthesised earlier [430, 431]. The structure has since been revised to L- -(3-uracilyl)alanine (LXXIX, isowillardiine) by examination of its ultraviolet absorption characteristics and chemical reactions [422] and substantiation by infrared, NMR, and mass spectrometry [432]. Its biological role has not yet been determined. 

A polymer is a macromolecule that is constructed by chemically linking together a sequent of molecular fragments. In simple synthetic polymers such as polyethylene or polystyrer all of the molecular fragments comprise the same basic unit (or monomer). Other poly me contain mixtures of monomers. Proteins, for example, are polypeptide chains in which eac unit is one of the twenty amino acids. Cross-linking between different chains gives rise to j-further variations in the constitution and structure of a polymer. All of these features me affect the overall properties of the molecule, sometimes in a dramatic way. Moreover, or... 

The sequence of amino acids in a peptide can be written using the three-letter code shown in Figure 45.3 or a one-letter code, both in common use. For example, the tripeptide, ala.ala.phe, could be abbreviated further to AAF Although peptides and proteins have chain-like structures, they seldom produce a simple linear system rather, the chains fold and wrap around each other to give complex shapes. The chemical nature of the various amino acid side groups dictates the way in which the chains fold to arrive at a thermodynamically most-favored state. 

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. 

The molecular basis for quasi-equivalent packing was revealed by the very first structure determination to high resolution of a spherical virus, tomato bushy stunt virus. The structure of this T = 3 virus was determined to 2.9 A resolution in 1978 by Stephen Harrison and co-workers at Harvard University. The virus shell contains 180 chemically identical polypeptide chains, each of 386 amino acid residues. Each polypeptide chain folds into distinct modules an internal domain R that is disordered in the structure, a region (a) that connects R with the S domain that forms the viral shell, and, finally, a domain P that projects out from the surface. The S and P domains are joined by a hinge region (Figure 16.8). 

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