RESUMO
To better understand the composite character of irradiated alanine ESR spectra, a comparative study of few simple amino acids is performed in order to identify the different radio-induced radicals and their proportions. A dedicated spin-trapping method coupled with High Performance Liquid Chromatography (HPLC) is developed and carried out on irradiated alanine, glycine and valine; labeled or not. This study leads us to obtain different isolated trapped radical spectra where hyperfine coupling constants could be evaluated. For alanine, only two species are identified with relative proportions around 97 and 3% in contradiction with recent published articles. The main species has a particularity on its hyperfine coupling constants when labeled carbons are used. Very high hyperfine coupling constants are observed with the carboxylic acid function carbon for the three studied amino acid.
Assuntos
Alanina/química , Radiólise de Impulso/métodos , Radiólise de Impulso/tendências , Cromatografia Líquida de Alta Pressão , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres/química , Concentração de Íons de Hidrogênio , Magnetismo , Soluções , Espectrofotometria Ultravioleta , Detecção de Spin , TemperaturaRESUMO
To better understand the composite character of amino acids EPR spectra, the radiolysis and reactions which occurred after irradiation of amino acids, a comparative EPR study of a few simple amino acids has been made in order to identify qualitatively and quantitatively the different radiation-induced radicals in amino acid powders. A spin-trapping methodology has been developed and carried out on irradiated glycine, alanine and valine.
Assuntos
Aminoácidos/efeitos da radiação , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres/efeitos da radiação , Alanina/química , Alanina/efeitos da radiação , Aminoácidos/química , Relação Dose-Resposta à Radiação , Radicais Livres/química , Raios gama , Glicina/química , Glicina/efeitos da radiação , Estrutura Molecular , Pós , Temperatura , Fatores de Tempo , Valina/química , Valina/efeitos da radiaçãoRESUMO
A laboratory bleaching experiment was performed in order to improve the method of ESR dating of sediments. Several sedimentary, volcanic, and granitic quartz samples showed consistent bleaching response for the exposure to halogen lamps. It was found that the most sensitive signals are the Ti-H and Ti-Na centers. There was no difference observed within the samples exposed to light filtered by several color glass plates, according to the present preliminary result.