Amino compounds radiolysis

To acquire further insight into the mechanism of the formation of these compounds, particularly of the protein-derived components, the radiolysis of several amino acids was studied. In all the amino acid studies, solutions or slurries of the acid were used in amounts corresponding to the... 

In all amino acid and peptide radiolysis, sulfur dioxide and carbonyl sulfide were found in varying amounts, but at present no explanation for the formation of these compounds can be offered. 

Interaction of the solute with radicals from the water is the first of a sequence of reactions which finally leads to stable products. Kinetic studies of the type cited give valuable information about the primary radical species and their relative reaction rates with molecules of different types. When sufficient data have been accumulated, it should be possible to predict the course of radiolysis in complex molecules. From the nature and yields of the products and by observing the effects on them of various factors such as concentration, pH, 02, and specific radical scavengers, it is often possible to speculate about the mechanisms by which products are formed. More often than not, this is a difficult problem because the products, even from relatively simple compounds, prove to be complex. Furthermore, it is often possible to produce more than one mechanism to fit the experimental data. The proteins are particularly difficult because of their complex structures. They contain approximately 20 different amino acids with an average of more than three carbon atoms in the side chains, which vary considerably in their structure hence, the possible number of products is large. For this reason, model compounds such as peptides and polyamino acids have been studied because they contain the peptide linkage but are free from the complications which arise from the diversity of the amino acid residues in a protein. A further practical difficulty which applies to chem-... 

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Electron Donation Ionization, OH-Adduct Formation, and Hydrogen Abstraction. Ionization of amino acids or peptides either through photolysis or radiolysis leads to cation radicals, the fate of which will be influenced by the nature of the compound and the medium. 

The first topic to be dealt with in this article dates back to the early days of pulse radiolysis and is concerned with intermediates generated from organic nitro and nitroso compounds in some elementary redox processes. This will be followed by a presentation of some most recent results on aminyl radicals derived from amino acids, exemplifying the diversity of possible reactions of a seemingly simple type of radicals. The third example on aniline and aniline radicals aims to demonstrate the potential of time-resolved resonance Raman spectroscopy. A common message of all these studies on N-centered radicals hints at the importance of acid/base properties of radicals. The aniline system, in particular, also draws attention to spin and charge distribution, and possible implications to the chemistry of radical species. 

Several other radiation protection agents are known. These compounds are typically amino thiols, similar to the natural amino acid cysteamine. They probably function as scavengers for the products of water radiolysis. Their effectiveness is evaluated by determination of the dose reduction factor (DRF), which is the ratio of LD5Q/3Q for protected and unprotected animals. Because of their chemical toxicity, many can o y be administered in small doses. 

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