Acids and Peptides

Modern methods of amino-acid and peptide analysis, have enabled the complete amino-acid sequence of a number of proteins to be worked out. The grosser structure can be determined by X-ray diffraction procedures. Proteins have molecular weights ranging from about 6 000 000 to 5 000 (although the dividing line between a protein and a peptide is ill defined). Edible proteins can be produced from petroleum and nutrients under fermentation. 

Carboxyl groups of ammo acids and peptides are normally protected as esters Methyl and ethyl esters are prepared by Fischer esterification Deprotection of methyl and ethyl esters is accomplished by hydrolysis m base Benzyl esters are a popular choice because they can also be removed by hydrogenolysis Thus a synthetic peptide protected at both... 

The p nitrophenol formed as a byproduct in this reaction is easily removed by extrac tion with dilute aqueous base Unlike free ammo acids and peptides protected peptides are not zwitteriomc and are more soluble m organic solvents than m water... 

This chapter revolves around proteins The first half describes the building blocks of proteins progressing through amino acids and peptides The second half deals with pro terns themselves... 

Derivatives such as 3-fluoro-4-nitropyridine [13505-01 -6] (396) or the 1-oxide [769-54-0] (397) have been used to characteri2e amino acids and peptides. 5-Eluoro-3-pyridinemethanol [22620-32-2] has been patented as an antihpolytic agent (398). A promising antidepressant, l-(3-fluoro-2-pyridyl)pipera2ine hydrochloride [85386-84-1] is based on 2-chloro-3-fluoropyridine [17282-04-1] (399). 

Specialist Periodical Reports Amino-Acids, Peptides, and Proteins, Royal Society of Chemistry, London,. Vols. 1-16 (1969-1983) Amino Acids and Peptides, Vols. 17-21 (1984-1990). 

The procedure described is essentially that of Shioiri and Yamada. Diphenyl phosphorazidate is a useful and versatile reagent in organic synthesis. It has been used for racemlzatlon-free peptide syntheses, thiol ester synthesis, a modified Curtius reaction, an esterification of a-substituted carboxylic acld, formation of diketoplperazines, alkyl azide synthesis, phosphorylation of alcohols and amines,and polymerization of amino acids and peptides. - Furthermore, diphenyl phosphorazidate acts as a nitrene source and as a 1,3-dipole.An example in the ring contraction of cyclic ketones to form cycloalkanecarboxylic acids is presented in the next procedure, this volume. 

It is known that not all reactions proceed in the same manner on all adsorbent layers because the material in the layer may promote or retard the reaction. Thus, Ganshirt [209] was able to show that caffeine and codeine phosphate could be detected on aluminium oxide by chlorination and treatment with benzidine, but that there was no reaction with the same reagent on silica gel. Again the detection of amino acids and peptides by ninhydrin is more sensitive on pure cellulose than it is on layers containing fluorescence indicators [210]. The NBP reagent (. v.) cannot be employed on Nano-Sil-Ci8-100-UV2S4 plates because the whole of the plate background becomes colored. 

Differences in the materials employed for the layers can also become evident when chemical reactions are performed on them. Thus, Macherey-Nagel report that the detection of amino acids and peptides by reaction with ninhydrin is less sensitive on layers containing luminescent or phosphorescent indicators compared to adsorbents which do not contain any indicator [7]. 

The detection limits for amino acids and peptides are between 50 and 200 pmol per chromatogram zone [9], 400 pg for 5-hydroxyindolylacetic acid [11] and 300 pg for dihydroxyergotoxin [19]. 

The last comprehensive review of the chemistry of oxazolones covered the literature through 1954. Most of the studies up to that time stemmed from either interest in the role of azlactones as precursors of a-amino acids and peptides or the monumental studies on penicillin, which, for a time, was thought to possess an oxazolone ring, rather than the correct jS-lactam moiety. 

Thomson MOW Click Organic Interactive to learn to estimate isoelectric points for simple amino acids and peptides. 

Cohn, E. J., and Edsall, J. T., Proteins, Amino Acids, and Peptides as Ions and Dipolar Ions, ... 

Stereoselectivity and reactivity in complexes of amino-acids and peptides. R. D. Gillard, Inorg. Chim. Acta, Rev., 1967,1,69-86 (102). 

Table 25 Compounds T8[(CH2)3NR)R2]8 obtained from the reaction of T8[(CH2)3NH3Cl]8 with Z-protected amino acids and peptides...

A. Interactions of [organotinllV)]" with amino acids and peptides 365... 

Nagy covered a large number of publications on the amino acids and peptides and on the other complexes discussed. 

The most widely studied interactions between biologically active ligands and organotin(lV) cations relate to the amino acids and their derivatives (N- or S-protected amino acids and peptides), though new data on several of the most commonly occurring amino acids are still being published. This is specially true for aqueous speciation studies. Nice and very detailed reviews were published in this area by Molloy and Nath. ... 

Applications of the oxalate-hydrogen peroxide chemiluminescence-based and fluorescence-based assays with NDA/CN derivatives to the analysis of amino acids and peptides are included. The sensitivity of the chemiluminescence and fluorescence methods is compared for several analytes. In general, peroxyoxalate chemiluminescence-based methods are 10 to 100 times more sensitive than their fluorescence-based counterparts. The chief limitation of chemiluminescence is that chemical excitation of the fluorophore apparently depends on its structure and oxidation potential. 

Michaeli, A. Feitelson, J. (1994). Reactivity of singlet oxygen toward amino acids and peptides. Photochemistry and Photobiology, Vol.59, No.3, (March 1994), pp. 284-289, ISSN 0031-8655. 

Park, E. Y. Murakami, H. Matsumura, Y. (2005). Effects of the addition of amino acids and peptides on lipid oxidation in a powdery model system. Journal of Agricultural and Food Chemistry, Vol. 53, No. 21, (September 2005), pp. 8334-8341 7, ISSN 0021-8561. 

Greenstein, J. P., Studies on multivalent amino acids and peptides, J. Biol. Chem., 118, 321-329, 1937. 

Selective protection and activation of amino acids and peptides has now reached a highly sophisticated level and requires specialised knowledge for the most efficient use. 

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