Amino Acids, Related Compounds, and Peptides

Duval (1956) has studied the spectra of amino acids recorded from a single drop of aqueous solution. Parker and Kirschenbaum (1960) have recorded the spectra of several a- and non-a-amino acids in water. The spectra of aqueous solutions of glycine, N-methylglycine (sarcosine), yV,yV-dimethylglycine, and yV,yV,A(-trimethylglycine (betaine) in dilferent states of ionization have also been recorded (Kirschenbaum, 1963). Another solvent which has been suggested for infrared spectral determination of amino acids is antimony trichloride (Lacher et al., 1954). 

The a-amino acids in the solid state or at their isoelectric points in aqueous solution exist almost totally as dipolar ions. Edsall s work in Raman spectroscopy of amino acids demonstrated conclusively their dipolar ionic structure (Edsall, 1936, 

1943 Edsall et al., 1950). Because of the dipolar ionic structure many amino acids have a characteristic band at 1587cm which is related to the —COO group, as well as a rather weak absorption at 2128cm which comes from NH frequencies in the —NHj ion (Thompson et al, 1950 Klotz and Gruen, 1948). 

Koegel et al (1957) have reviewed the infrared absorption of the optically active and racemic straight-chain a-amino acids after presenting an earlier comprehensive paper (1955) on the spectra of about 50 such compounds and their derivatives. In every case these workers found that the spectrum of an L-amino acid was identical with that of the D-isomer in the range 5000 to 667 cm .  

Spectra—Structure Correlations and Other Structural Considerations 

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In Sect. 6.1, we defined a peptide as any compound produced by amide formation between a carboxy group of one amino acid and an amino group of another. Our definition is explicit as far as the relation between component residues is concerned, but is incomplete since the definition of amino acids is left open. In Sect. 6.3 and 6.4, we used a narrow definition of amino acids (i.e., proteinogenic a-amino acids). In contrast, the peptides examined... 

Chapman and Hall Chemical Database Chapman and Hall, Ltd. Dialog Dictionary of Organic Compounds (5th ed.), Dictionary of OrganometalUc Compounds, Carbohydrates, Amino Acids, Peptides, Dictionary of Antibiotics and Related Compounds, and Dictionary of Organophosphorus Compounds... 

Obtaining quantitative yields in amino acid coupling steps and in the repetitive A -amino group deprotection is the main problem in stepwise solid-phase peptide synthesis (SPPS). Since purification is only possible in the last step accumulation of deleted peptides and truncated sequences occurs. Therefore these undesired compounds are present in the crude mixture after final cleavage from the solid support are usually closely related to the target peptide in their physical properties, resulting in difficult purification steps. 

There have been several reports of lipoprotein fractions associated with the microsomal fraction 50, 59) which were rapidly labeled by amino acids in vivo, and which also showed rapid turnover. Such a lipoprotein fraction was also recently reported in bacterial membranes 14S). Amino acids, and possibly peptides, bound to phospholipids have also been reported in Penicillium chrysogenum 370) and in the membranes of L. casei 300). The relation of these compounds to protein synthesis has not been investigated, but their finding does open the interesting possibility that, in analogy with the ribose hydroxyls of RNA, the free hydroxyls of phospholipid glycerol mi t serve to carry activated amino acids. 

The azlactones of a-benzoylaminocinnamic acids have traditionally been prepared by the action of hippuric acid (1, Ri = Ph) and acetic anhydride upon aromatic aldehydes, usually in the presence of sodium acetate. The formation of the oxazolone (2) in Erlenmeyer-Plochl synthesis is supported by good evidence. The method is a way to important intermediate products used in the synthesis of a-amino acids, peptides and related compounds. The aldol condensation reaction of azlactones (2) with carbonyl compounds is often followed by hydrolysis to provide unsaturated a-acylamino acid (4). Reduction yields the corresponding amino acid (6), while drastic hydrolysis gives the a-0X0 acid (5). ... 

Polar organic compounds such as amino acids normally do not polymerize in water because of dipole-dipole interactions. However, polymerization of amino acids to peptides may occur on clay surfaces. For example, Degens and Metheja51 found kaolinite to serve as a catalyst for the polymerization of amino acids to peptides. In natural systems, Cu2+ is not very likely to exist in significant concentrations. However, Fe3+ may be present in the deep-well environment in sufficient amounts to enhance the adsorption of phenol, benzene, and related aromatics. Wastes from resinmanufacturing facilities, food-processing plants, pharmaceutical plants, and other types of chemical plants occasionally contain resin-like materials that may polymerize to form solids at deep-well-injection pressures and temperatures. 

One advantage of the coenzyme amino acid chimera approach is that it is compatible with solid phase peptide synthesis. Consequently, the reactive functionality can be readily and selectively delivered to any site in the peptide. Additionally, both natural and unnatural residues can be incorporated throughout the peptide scaffold, and related compounds can be investigated rapidly by combinatorial synthesis techniques. 

The main genera responsible for freshwater toxic blooms are Microcystis, Anabaena, Aphanizomenon and Oscillatoria. Toxins produced include 1. anatoxins, alkaloids and peptides of Anabaena 2. the peptide microcystin and related peptides of Microcystis 3. aphantoxins, compounds of Aphanizomenon with properties similar to some paralytic shellfish poisons. Properties of Oscillatoria toxin suggest they are peptides similar to those of Microcystis. Microcystis toxins are peptides (M.W. approx. 1200) which contain three invariant D-amino acids, alanine, erythro-3-methyl aspartic and glutamic acids, two variant L-amino acids, N-methyl dehydro alanine and a 3-amino acid. Individual toxic strains have one or more multiples of this peptide toxin. The one anatoxin characterized is a bicylic secondary amine called anatoxin-a (M.W. 165). The aphantoxin isolated in our laboratory contains two main toxic fractions. On TLC and HPLC the fractions have the same characteristics as saxitoxin and neosaxitoxin. 

Systematic substitutive nomenclature may be used to name all organic molecules. However, those that are of animal or vegetable origin have often received trivial names, such as cholesterol, oxytocin and glucose. Biochemical nomenclature is based upon such trivial names, which are either substitutively modified in accordance with the principles, rules and conventions described in Chapter 4, Section 4.5 (p. 70), or transformed and simplified into names of stereoparent hydrides, i.e. parent hydrides of a specific stereochemistry. These names are then modified by the rules of substitutive nomenclature. Three classes of compound will be discussed here to illustrate the basic approach carbohydrates amino acids and peptides and lipids. For details, see Biochemical Nomenclature and Related Documents, 2nd Edition, Portland Press, London (1992). 

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