Proteins pyrolysis

Pyrolysis of a-amino acids has significant implications in the interpretation of the results of peptide and protein pyrolysis. Amino acid thermal decomposition takes place through four main fragmentation pathways as shown below ... 

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 this reaction, the formation of two series of compounds is proposed because in the chromatographic separations of polypeptide pyrolysates, an additional peak is noticed for each 3-alkenyl-5-alkyl-pyrrolidin-2,4-dione. This second peak is assigned to the corresponding 2,4-dialkyl-3,5-diketopyrroline (position isomers are not possible when R2 and R3 are identical) [1]. The list of different compounds from these two classes that may be formed during laser irradiation of different mammalian tissues [13a] due to peptide (protein) pyrolysis and the amino acid pair that can generate them is given in Table 12.2.3. 

Polypeptide pyrolysis is important in connection with protein pyrolysis, but some studies were done on particular peptides such as actinomycins, which have antibiotic and cytostatic properties. Several actinomycins are known, the formulas for some of them being represented by ... 

The silylated pyrolysate of the two albumins shows the presence of levoglucosan, which is a marker for the sugar moiety indicating the presence of carbohydrates. Besides the compounds seen by GC techniques, probably protein pyrolysates contain larger molecules, which are kept in the char that is formed in abundance in protein pyrolysis. 

The compounds coming from protein and shown in Tables 12.3.1 to and 12.3.4 are small molecules, the amino acids (such as proline), or DKP type compounds. This type of information from protein pyrolysis has been commonly us for structure elucidation, protein identification, and differentiation between different proteinaceous materials (hair, microorganisms, etc.). However, the information on the protein structure is limited to amino acid content and to a certain extent to the amino acid sequence in the protein. 

The presence of nitrites has both a positive and negative impact on food safety. On one hand, in many countries, a correlation between stomach and liver cancers, induced probably by nitrosamines, and the amount of nitrites consumed is observed (Fine et al., 1982). On the other hand, nitrites inhibit the growth of Clostridium botulinum, thus reducing the risk of food contamination by botulinum toxins. Moreover, under the acidic conditions of the stomach, where they are involved in the formation of carcinogenic nitrosamines, nitrites are capable of neutralizing carcinogens formed as a result of protein pyrolysis (Pariza, 1982). 

The constraint of extruding whey protein above the useful texturization range is keeping the temperature below the point where pyrolysis will occur as evidenced by relatively constant nitrogen content. However, texturized whey products are sometimes extruded at 150 °C to form... 

Goodacre, R. Karim, A. Kaderbhai, M. A. Kell, D. B. Rapid and quantitative analysis of recombinant protein expression using pyrolysis mass spectrometry and artificial neural networks Application to mammalian cytochrome b5 in Escherichia coli. J. Biotechnol. 1994,34,185-193. 

The Curie point of the alloy is determined by the iron-to-nickel ratio an Fe Ni ratio of 50 50 was used to give a Curie point of 530°C. This pyrolysis temperature was chosen because it has been shown22 to give a balance between fragmentation from polysaccharides and protein fractions. Foils with Curie points of 300°C to 1000°C are commercially available (Figure 15.2). How-... 

It is therefore not surprising that the interest in PyMS as a typing tool diminished at the turn of the twenty-first century and hence why taxonomists have turned to MS-based methods that use soft ionization methods such as electrospray ionization (ESI-MS) and matrix-assisted laser desorption ionization (MALDI MS). These methods generate information-rich spectra of metabolites and proteins, and because the molecular ion is seen, the potential for biomarker discovery is being realized. The analyses of ESI-MS and MALDI-MS data will still need chemometric methods, and it is hoped that researchers in these areas can look back and learn from the many PyMS studies where machine learning was absolutely necessary to turn the complex pyrolysis MS data into knowledge of bacterial identities. 

McGovern, A. C. Ernill, R. Kara, B. V. Kell, D. B. Goodacre, R. Rapid analysis of the expression of heterologous proteins in Escherichia coli using pyrolysis mass spectrometry and Fourier transform infrared spectroscopy with chemometrics Application to a2- interferon production. J. Biotechnol. 1999, 72,157-167. 

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... 

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... 

McGovern et al.26 analyzed the expression of heterologous proteins in E. coli via pyrolysis mass spectrometry and FT-IR. The application was to a2-interferon production. To analyze the data, artificial neural networks (ANN) and PLS were utilized. Because cell pastes contain more mass than the supernatant, these were used for quantitative analyses. Both the MS and IR data were difficult to interpret, but the chemometrics used allowed researchers to gain some knowledge of the process. The authors show graphics indicating the ability to follow production via either technique. 

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. 

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