Espectroscopia Raman no cristal do nucleosídeo adenosina submetido a altas pressões

Detalhes bibliográficos
Ano de defesa: 2017
Autor(a) principal: Vasconcelos, Daniel Linhares Militão
Orientador(a): Não Informado pela instituição
Banca de defesa: Não Informado pela instituição
Tipo de documento: Dissertação
Tipo de acesso: Acesso aberto
Idioma: por
Instituição de defesa: Não Informado pela instituição
Programa de Pós-Graduação: Não Informado pela instituição
Departamento: Não Informado pela instituição
País: Não Informado pela instituição
Palavras-chave em Português:
Link de acesso: http://www.repositorio.ufc.br/handle/riufc/22535
Resumo: Nucleosides are organic compounds formed by a nitrogenous base and a sugar. In the present work a detailed study was carried out regarding the vibrational modes of the crystal of the nucleoside adenosine (C10H13N5O4) submitted to high pressures. Initially the reagent which was in powder form was crystallized by the slow evaporation method of the solvent. In the obtained crystal Raman spectroscopy measurements were performed. The spectral region investigated covered the interval between 20 cm-1 and 1700 cm-1 , having been observed 49 vibrational modes. The classification of these modes was done with reference to work done with the same material, as well as investigations in other nucleosides such as thymidine and cytosine. In order to subject the material to high pressures a pressure cell with diamond anvil was used and the nujol was used as the compressor medium. The study was performed with a pressure ranging from 1 atm to 7.2 GPa. The results inferred from the Raman spectra show that around 2.4 GPa some vibrational modes disappear, while others appear, besides discontinuities in the evolution of frequencies of several normal modes of vibration. This changes suggest a structural phase transition in adenosine occurring around 2.4 GPa, reversible, and without sample destruction, either during compression or during decompression. The fact that frequency discontinuities occur with modes associated with both nucleic acid and sugar suggests that the phase transition involves conformational changes of the two units of the adenosine molecule. As a consequence, it can be inferred that the change of symmetry in the unit cell involves the various hydrogen bonds, which ultimately constitute the intermolecular connections between the various molecules therein.