Proteins, Peptides, Amino Acids

This chapter deals with the very important a-amino acids, the building blocks of the proteins that are necessary for the function and structure of living ceils. Enzymes, the highly specific biochemical catalysts are proteins. or-Amino acids are dipolar ions (zwitterions), RCH(N H,)COO , as is indicated by their crystallinity, high melting point, and solubility in water rather than in nonpolar solvents. The standard (naturally occurring) amino acids are listed in Table 21-1 those marked with an asterisk are essential amino acids that cannot be synthesized in the body and so must be in the diet. They have 1° NHj s except for proline and hydroxyproline (2°). They have different R groups. 

Except for glycine, they are chiral molecules with the l or S (or R, for cysteine and cystine) configuration at the a C. 

Problem 21.1 (a) Find the absolute configuration of the following t-amino acids  

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By far the majority of carbohydrate material in nature occurs in the form of polysaccharides. By our definition, polysaccharides include not only those substances composed only of glycosidically linked sugar residues but also molecules that contain polymeric saccharide structures linked via covalent bonds to amino acids, peptides, proteins, lipids, and other structures. 

Compounds that can be converted to chloramines [1-4] e.g. amino acids, peptides, proteins and derivatives [5-13]... 

Udenfriend, S., Stein, S., Bohlen, P., Dairman, W., Leimgruber, W., and Weigele, M., Fluorescamine a reagent for assay of amino acids, peptides, proteins, and primary amines in the picomole range, Science, 178, 871, 1972. 

HPLC is frequently employed in the analysis of amino acids, peptides, proteins, nucleic acids, and nucleotides. HPLC is also often used to analyze for drugs in biological samples (see Workplace Scene 16.2). Due to the complex nature of the molecules to be analyzed, these techniques tend to be more complex than HPLC applications in other areas of analytical chemistry. For example, separation of nucleotides or amino acids is more difficult than testing for caffeine in beverages, even though the same instrument and same general methods would be employed. A variety of columns and mobile phases are regularly employed. 

As to the origins of the major N compounds identified, it is possible that at least a portion of some of these compounds are pyrolysis products of amino acids, peptides, proteins, [18] and porphyrins (a component of chlorophyll), [19] or originate from the microbial decomposition of plant lignins and other phenolics in the presence of ammonia. [20] Of considerable interest are the identifications aromatic and aliphatic nitriles. Nitriles can be formed from amines with the loss of 2 H2, from amides with the loss of H20, and also by reacting n-alkanoic acid with NH3. [21] The detection of long-chain alkyl- and dialkyl-nitriles points to the presence in the soil or SOM of long-chain amines... 

Muscle protein amino acids peptides, proteins (including cytokines, acute phase proteins)... 

AMINO ACIDS, PEPTIDES PROTEINS Recommended nomenclature and symbolism for amino acids and peptides J. Biol Chem. (1985) 260, 14-42 Biochemistry (1975) 14, 449-462 Abbreviations and symbols for the description of the conformation of polypeptide chains /. Biol Chem. (1970) 245, 6489-6497 Nomenclature of iron-sulfur proteins Eur. J. Biochem. (1979) 93, 427-430 Corrections Eur. J. Biochem. (1979) 102, 315 Nomenclature of peptide hormones J. Biol Chem. (1975) 250, 3215-3216 Nomenclature of human immunoglobulins Eur. J. Biochem. (1974) 45, 5-6 Recommended nomenclature of glycoproteins, glyco-peptides, and peptidoglycans /. Biol Chem. (1987) 262, 13-18 Recommended nomenclature of electron-transfer proteins... 

Sugars, glycoproteins, and diol-containing compounds Nucleotide-binding proteins, and enzymes Amino acids, peptides, proteins, and other agents that can bind to metal ions... 

Bayley,P.M. Amino-Acids, Peptides, Proteins. 1972,4,pp253-286. 

B. Kolb, New Tech. Amino Acid, Peptide, Protein Anal., 129,... 

In theory, if the net charge, q, on a molecule is known, it should be possible to measure / and obtain information about the hydrodynamic size and shape of that molecule by investigating its mobility in an electric field. Attempts to define /by electrophoresis have not been successful, primarily because Equation 4.3 does not adequately describe the electrophoretic process. Important factors that are not accounted for in the equation are interaction of migrating molecules with the support medium and shielding of the molecules by buffer ions. This means that electrophoresis is not useful for describing specific details about the shape of a molecule. Instead, it has been applied to the analysis of purity and size of macromolecules. Each molecule in a mixture is expected to have a unique charge and size, and its mobility in an electric field will therefore be unique. This expectation forms the basis for analysis and separation by all electrophoretic methods. The technique is especially useful for the analysis of amino acids, peptides, proteins, nucleotides, nucleic acids, and other charged molecules. 

AMINO ACIDS, PEPTIDES, PROTEINS, ENZYMES, AND NUCLEIC ACIDS... 

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