Amino acids pyrolysis

Methods were described for HPLC determination of the mutagenic and carcinogenic a-carbolines (56,57), y-carbolines (58,59)155 160, and other products of amino acid pyrolysis found in cigarette smoke, diesel exhaust and cooked foods and phenazines (60, 61) present as impurities of certain pesticides161. These compounds were also determined in human plasma, urine and bile161,162. 

Heterocyclic aroma compounds found in meat primarily arise from interactions between mono- and dicarbonyl compounds, H2S and ammonia. The carbonyl compounds are derived from the Maillard reaction, including Strecker degradation of amino acids, oxidation of lipids and aldolization reactions. H2S is produced by thermal degradation of sulfur amino acids and ammonia by amino acid pyrolysis. 

The results for amino acids show that the main pyrolysis products are similar to the ion fragmentation that takes place upon electron impact. For the case of peptides and proteins, most of the effort has been done in obtaining ions of large fragments in order to account as much as possible for the protein structure [24]. Several mass spectra of substituted diketopiperazines obtained from peptide pyrolysis are shown in Figures 3.6.6 a to 3.6.6 f. The fragments generated in their mass spectra are similar to some small molecules obtained in amino acid pyrolysis. 

The amino acid pyrolysis is relevant for protein pyrolysis because certain compounds in the pyrolysate are the same when the substance to be pyrolysed is the amino acid or a peptide formed from that specific amino acid (see Section 13.2). The main pyrolysis products of several amino acids are given in Table 12.1.2 [3,4]. 

In the mid-1970s, pyrolysis studies with several amino acids led to the isolation and identification of several additional polycyclic A-heterocyclic compounds which are reported not only to be tumorigenic to mouse skin but also to show inordinately high mutagenicity when tested in the Ames bioassay with Salmonella typhimurium. The impetus for these particular amino acid pyrolysis studies was not the attempt to define the relationship between tobacco leaf precursors and tobacco smoke components but the observation that the extracts of broiled, fried, or roasted foodstuffs (meat, fish, poultry, etc.) were highly mutagenic in the Ames bioassay Salmonella typhimurium). These A-heterocyclic... 

Table lV.B-4 lists several polynuclear (V-heterocyclic amines that exhibit extremely high mutagenicity levels in the Ames bioassay, are amino acid pyrolysis products, and have been identihed in various broiled, fried, or roasted foodstuffs as well as in CSC [Sugimura (3828c)]. On a per microgram basis, B[fl]P in the Ames bioassay with Salmonella typhimu-rium (Strain TA 98) shows about 200 revertants/pg. Several of the amino acid-derived compounds in Table lV.B-4 exceed the B[fl]P effect with the TA 98 strain by factors ranging from about 10 to over 2100. 

More recent amino acid pyrolysis studies led to the isolation and identification of several 7V-heterocyclic amines reported not only to be tnmorigenic to mouse skin bnt also to show inordinately high mntagenicity [Ames bioassay... 

Goodacre, R. Edmonds, A. N. Kell, D. B. Quantitative analysis of the pyrolysis-mass spectra of complex mixtures using artificial neural networks Application to amino acids in glycogen. J. Anal. Appl. Pyrolysis 1993, 26, 93-114. 

In other words, a synthetic route to polypeptides which requires only HCN and water is presented preformed a-amino acids are not necessary. According to Matthews, the pyrolysis of cyanide polymers can give nitrogen-containing heterocycles with purine and pyrimidine structures in other words, the HCN world ... 

The question of the stability of the biomolecules is a vital one. Could they really have survived the tremendous energies which would have been set free (in the form of shock waves and/or heat) on the impact of a meteorite Blank et al. (2000) developed a special technique to try and answer this question. They used an 80-mm cannon to produce the shock waves the shocked solution contained the two amino acids lysine and norvaline, which had been found in the Murchison meteorite. Small amounts of the amino acids survived the bombardment , lysine seeming to be a little more robust. In other experiments, the amino acids aminobutyric acid, proline and phenylalanine were subjected to shock waves the first of the three was most stable, the last the most reactive. The products included amino acid dimers as well as cyclic diketopiperazine. The kinetic behaviour of the amino acids differs pressure seems to have a greater effect on the reaction pathway than temperature. As had been recognized earlier, the effect of pressure would have slowed down certain decomposition reactions, such as pyrolysis and decarboxylation (Blank et al., 2001). 

X. Zang, J.C. Brown, J.D.H. van Heemst, A. Palumbo, P.G. Hatcher, Characterization of Amino Acids and Proteinaceous Materials using Online Tetramethylammonium Hydroxide (TMAH) Thermochemolysis and Gas Chromatography Mass Spectrometry Technique, Journal of Analytical and Applied Pyrolysis, 61, 181 193 (2001). 

N. Gallois, J. Templier and S. Derenne, Pyrolysis gas chromatography mass spectrometry of the 20 protein amino acids in the presence of TMAH, J. Anal. Appl. Pyrol., 80, 216 230... 

G. Chiavari, D. Fabbri and S. Prati, Gas chromatographic mass spectrometry analysis of products arising from pyrolysis of amino acid in the presence of hexamethyldisilazane, J. 

First attempts to combine pyrolysis with in situ HMDS silylation of organic art materials were reported by Chiavari et al., who were successful in obtaining trimethylsilyl derivatives of fatty acids [52], amino acids [53] and carbohydrates [54]. The same authors also applied pyrolysis-silylation to the analysis of different kinds of natural resins and for each of them diagnostic silylated compounds were identified, even if many were difficult to assign precise structures [55],... 

Nitrogen-containing analytes in a FIA system, e.g. amino acids, as they emerge from the LC column, are introduced into a pyrolysis oven under argon atmosphere. The products... 

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... 

Presently about 20 different mutagenic and/or carcinogenic heterocyclic amines (HAs) have been isolated from various heat-processed foods. One class of these HAs is formed by pyrolysis of proteins or some amino acids. These HAs are amino-carbolines (Figure 13.7), and have been identified in grilled, broiled, baked, and fried meat and fish products, in meat sauces and bouillons, as well as in pyrolyzed proteins, glutamate, lysine, phenylalanine, tryptophan, ornithine, and creatine. 

Dean, M. A., A. S. Dhaliwal, and W. R. Jones. Effects of Zingiberaceae rhizome extract of the infectivity of cyanophage LPP-1. Trans 111 State Acad Sci Suppl 1987 80 Abstr 83. Morita, K., M. Hara, and T. Kada. Studies on natural desmutagens screening for vegetable and fruits factors active in inactivation of mutagenic pyrolysis products from amino acids. Agr Biol Chem 1978 42(6) 1235-1238. 

Gl (MW >5000). Most of the pyrolysis fragments found in this fraction are derived from the three general classes just mentioned. Pyrrole and methylpyrrole originate from proteinaceous material such as polypeptides as well as from single amino acids such as proline and hydroxyproline. A quantitative relationship between amino acid hydrolyzable content and pyrrole abundance was established by Bracewell (20) for some Scottish brown forest soils, and such a correlation probably could be established for water. 

Pyrolysis of CH4 and NH3 gives very low yields of amino acids. The pyrolysis conditions are from 800° to 1200°C with contact times of a second or less. However, the pyrolysis of CH4 and other hydrocarbons gives good yields of benzene, phenylacetylene, and many other hydrocarbons. It can be shown that phenylacetylene would be converted to phenylalanine and tyrosine in the primitive ocean.17 Pyrolysis of the hydrocarbons in the presence of NH3 gives substantial yields of indole, which can be converted to tryptophan in the primitive ocean. 

Table I. Mutagenic activity of condensate of smoke formed by pyrolysis of biomacromolecules and of amino acids...

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