Amino acid decomposition temperature

The TVD curves of selected amino acids were determined by Contarini and Wendlandt (121). A comparison of the TVD and DSC peak temperature is shown in Table 11.8. The TVD peak temperatures are somewhat higher than those obtained by DSC. Obviously, the kinetics of the electrodedecomposition produces) reaction are different from those of the decomposition reaction. These electrode reactions probably involve one or more diffusion steps between the electrode surface and the amino acid or amino acid decomposition produces), which would be different from the decomposition kinetics themselves. The leading edge of the TVD curve peaks is reproducible to within +1-2%. However, after the peak maximum temperature is attained, the reproducibility falls to within +20% in some cases. This is related to the electrode-amino acid decomposition products interface, which, due to the nature of the reaction, would not be expected to be reproducible. The trailing edge portion of the curve also consists of several shoulder peaks that may be related to the consecutive and/or concurrent reactions previously described in the DSC curves. These reactions could produce decomposition products that would react with the aluminum metal electrode surface. 

Benzyioxycarbonyi chioride (Cbz-Ci, benzyi cbioroformate) [501-53-1] M 170.6, b 103 /20mm, d 1.195, n 1.5190. Commercial material is better than 95% pure and may contain some toluene, benzyl alcohol, benzyl chloride and HCl. After long storage (e.g. two years at 4 , Greenstein and Winitz [The Chemistry of the Amino Acids Voi 2 p. 890, J Wiley and Sons NY, 1961] recommended that the liquid should be flushed with a stream of dry air, filtered and stored over sodium sulfate to remove CO2 and HCl which are formed by decomposition. It may further be distilled from an oil bath at a temperature below 85 because Thiel and Dent [Annalen 301 257 1898] stated that benzyioxycarbonyi chloride decarboxylates to benzyl chloride slowly at 100 and vigorously at 155 . Redistillation at higher vac below 85 yields material which shows no other peaks than those of benzyioxycarbonyi chloride by NMR spectroscopy. LACHRYMATORY and TOXIC. 

The mesoionic azolides are reported to be relatively stable toward hydrolytic decomposition, but more reactive against amines than the corresponding imidazo-lides.[194] -Protection of the amino compounds (for example by the Boc group) takes place smoothly at room temperature in about one to five hours and with high yield. The amino acids are introduced as sodium salts in aqueous acetone. 

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). 

E. L. Shock (1990) provides a different interpretation of these results he criticizes that the redox state of the reaction mixture was not checked in the Miller/Bada experiments. Shock also states that simple thermodynamic calculations show that the Miller/Bada theory does not stand up. To use terms like instability and decomposition is not correct when chemical compounds (here amino acids) are present in aqueous solution under extreme conditions and are aiming at a metastable equilibrium. Shock considers that oxidized and metastable carbon and nitrogen compounds are of greater importance in hydrothermal systems than are reduced compounds. In the interior of the Earth, CO2 and N2 are in stable redox equilibrium with substances such as amino acids and carboxylic acids, while reduced compounds such as CH4 and NH3 are not. The explanation lies in the oxidation state of the lithosphere. Shock considers the two mineral systems FMQ and PPM discussed above as particularly important for the system seawater/basalt rock. The FMQ system acts as a buffer in the oceanic crust. At depths of around 1.3 km, the PPM system probably becomes active, i.e., N2 and CO2 are the dominant species in stable equilibrium conditions at temperatures above 548 K. When the temperature of hydrothermal solutions falls (below about 548 K), they probably pass through a stability field in which CH4 and NII3 predominate. If kinetic factors block the achievement of equilibrium, metastable compounds such as alkanes, carboxylic acids, alkyl benzenes and amino acids are formed between 423 and 293 K. 

The application of olefin metathesis to the synthesis of piperidines continues to be widely employed. The use of ring closing metathesis (RCM) in the synthesis of fluorovinyl-containing a,P-unsaturated lactams 148 and cyclic amino acid derivatives 149 is shown below. A key improvement in these reactions is the addition of the Grubbs 2nd generation catalyst (G2) in small portions during the reaction to compensate for catalyst decomposition that occurs at elevated reaction temperatures <06EJOl 166>. 

The effect of temperature on the rate of racemization of amino acids in fossils was investigated and the implications of the findings on fossil dating were analyzed313. The high rate of conversion of L-aspartic acid into its D-isomer, observed in uncontaminated bone samples taken from catacombs in Rome (IV century BC) was attributed to collagen decomposition due to the humidity of the catacombs314. 

The naturally occurring amino acids are very polar, and cannot be separated as the free compounds by GC at a temperature below decomposition. If the polar groups in the molecule are chemically modified to produce a more volatile derivative a suitable temperature is then possible. Weinstein (25) reviews all the various derivatives which may be formed from amino acids and the GC conditions necessary to separate them. In actual practice only three derivatives are in popular use. These include the N-heptafluorobutyryl n-propyl ester derivatives, the N-trimethyl-silyl ether derivatives, and the n-trifluoroacetyl n-butyl ester derivatives. 

The fructose-amino acids are fluffy, non-crystalline, slightly hygroscopic white powders. They are stable at 80° for several hours more drastic heating leads to decomposition. They reduce ferricyanide in 0.1N alkali at room temperature. The usual route of preparation is via the synthetic process followed by isolation of the product by chromatography on Dowex 50. 

Characteristic thermogram patterns were obtained10 by TPD MS, which allows us to observe details of BSA decomposition and the two monosaccharides in the condensed state. Thermal decomposition patterns for several components of the BSA mass spectrum in condensed and adsorbed states are presented in Figures 4 and 5. After individual adsorption of BSA on fumed silica the pattern of BSA decomposition changed slightly, and could still be used to identify the nanocomposites. The only exception is the temperature dependence of mass line at 34 M/z, which corresponds to the molecular ion H2S+ resulting from decomposition of sulfur-containing amino acids of BSA. 

The silylation of amino acids with BSTFA was studied in detail by Gehrke and coworkers [254—256]. BSTFA—acetonitrile (1 1) was applied first and fourteen amino acids were silylated at 135°C for 15 min. Glu, Arg, Lys, Trp, His and Cys, however, require up to 4 h, in order for measurable peaks to be obtained in the chromatogram. Despite such a long reaction, Gly and Glu gave two peaks and also it was difficult to separate the tris-TMS derivative of Gly from the derivatives of lie and Pro. The influence of polar and non-polar solvents was demonstrated later and was decisive mainly with respect to uniformity of the products. Only the bis-TMS derivative was produced in hexane, methylene chloride, chloroform and 1,2-dichloroethane bis- and tris-derivatives were produced in six more polar solvents. On the other hand, Arg did not provide any peak in the less polar solvents that were used and only one peak in the six more polar solvents. The best and most reproducible results were obtained when silylating seventeen amino acids with BSTFA—acetonitrile (1 1) at 150°C for 15 min 2.5 h at 150°C were necessary for the reproducible derivatization of Gly, Arg, and Glu. These reaction conditions were recommended for the analysis of all twenty amino acids. The TMS derivatives of amino acids were found to be stable on storing them in a sealed vial at room temperature for 8 days, with no decomposition. 

The factors that affect the ability of microorganisms to decompose organic material include type of organic material, temperature, pH, and redox potential (Eh). Fungi and actinomycetes are primarily responsible for the initial decomposition of organic waste. After that, bacteria are able to produce protease, a proteolytic enzyme which breaks protein down into simple compounds such as amino acids. The amino acids are absorbed by the microorganisms and ammonia is released by the following reactions ... 

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