RESUMO
Several recent computational studies have tried to explain the observed selectivity in radical damage to proteins. In this work we use Density Functional Theory and Transition State Theory including tunnelling corrections, reaction path degeneracy, the effect of diffusion, and the role of free radicals to get further insights into this important topic. The reaction between a leucine derivative and free radicals of biological significance, in aqueous and lipid media, has been investigated. Both thermochemical and kinetic analyses, in both hydrophilic and hydrophobic environments, have been carried out. DPPH, ËOOH, ËOOCH3, ËOOCH2Cl, ËOOCHCl2 and ËOOCHCH2 radicals do not react with the target molecule. The reactions are proposed to be kinetically controlled. The leucine gamma site was the most reactive for the reactions with ËN3, ËOOCCl3, ËOCH3, ËOCH2Cl, and ËOCHCl2 radicals, with rate constants equal to 1.97 × 10(5), 3.24 × 10(4), 6.68 × 10(5), 5.98 × 10(6) and 8.87 × 10(8) M(-1) s(-1), respectively, in aqueous solution. The ËCl, ËOH and ËOCCl3 radicals react with leucine at the beta, gamma, and delta positions at rates close to the diffusion limit with the alpha position which is the slowest path and the most thermodynamically favored. The presented results confirm that the Bell-Evans-Polanyi principle does not apply for the reactions between amino acid residues and free radicals. Regarding the influence of the environment on the reactivity of the studied series of free radicals towards leucine residues, it is concluded that hydrophilic media slightly lower the reactivity of the studied radicals, compared to hydrophobic ones, albeit the trends in reactivity are very similar.
Assuntos
Radicais Livres/química , Leucina/análise , Proteínas/química , Interações Hidrofóbicas e Hidrofílicas , Cinética , Lipídeos/química , Modelos Moleculares , Estresse Oxidativo , Termodinâmica , Água/químicaAssuntos
Humanos , Animais , Masculino , Feminino , Pré-Escolar , Criança , Adulto Jovem , Adulto , Gatos , Desenvolvimento de Programas , Materiais Educativos e de Divulgação , Cursos de Capacitação , Animais de Estimação , Cães , Gatos , Saúde PúblicaAssuntos
Masculino , Feminino , Humanos , Animais , Pré-Escolar , Criança , Adulto Jovem , Adulto , Gatos , Materiais Educativos e de Divulgação , Desenvolvimento de Programas , Cursos de Capacitação , Gatos , Cães , Animais de Estimação , Saúde PúblicaRESUMO
Our experience with the air contrast examination in the cancer of colon and rectum diagnoses is showed. The colaboration among radiologist, endoscopist, pathologist and surgeon is important. In the large bowel tumors diagnosis, the radiologic and endoscopic prodedures should be evaluated together. The double colonic contrast has showed in our experience, better results than with the barium enema. Over 31 patients with both studies, we obtained 13 false negatives (with barium enema, doing then the double colonic contrast became positive 12 (92.4%).
Assuntos
Adenocarcinoma/diagnóstico , Neoplasias do Colo/diagnóstico , Neoplasias Retais/diagnóstico , Adenocarcinoma/diagnóstico por imagem , Adenocarcinoma/patologia , Adulto , Idoso , Sulfato de Bário , Biópsia , Neoplasias do Colo/diagnóstico por imagem , Neoplasias do Colo/patologia , Meios de Contraste , Endoscopia , Humanos , Pessoa de Meia-Idade , Radiografia , Neoplasias Retais/diagnóstico por imagem , Neoplasias Retais/patologiaRESUMO
Our experience with the air contrast examination in the cancer of colon and rectum diagnoses is showed. The colaboration among radiologist, endoscopist, pathologist and surgeon is important. In the large bowel tumors diagnosis, the radiologic and endoscopic prodedures should be evaluated together. The double colonic contrast has showed in our experience, better results than with the barium enema. Over 31 patients with both studies, we obtained 13 false negatives (with barium enema, doing then the double colonic contrast became positive 12 (92.4
).
RESUMO
Our experience with the air contrast examination in the cancer of colon and rectum diagnoses is showed. The colaboration among radiologist, endoscopist, pathologist and surgeon is important. In the large bowel tumors diagnosis, the radiologic and endoscopic prodedures should be evaluated together. The double colonic contrast has showed in our experience, better results than with the barium enema. Over 31 patients with both studies, we obtained 13 false negatives (with barium enema, doing then the double colonic contrast became positive 12 (92.4