RESUMO
The unexpected formation of trisaccharide nucleosides during synthesis of purine 5'-O-beta-D-ribofuranosylnucleosides in the presence of Lewis acids was observed.
Assuntos
Oligossacarídeos/química , Nucleosídeos de Purina/síntese química , Sequência de Carboidratos , Dados de Sequência Molecular , Nucleosídeos de Purina/químicaAssuntos
DNA Polimerase Dirigida por DNA/metabolismo , Nucleotídeos de Timina/metabolismo , Animais , Vírus da Mieloblastose Aviária/metabolismo , Replicação do DNA , Indicadores e Reagentes , Estrutura Molecular , DNA Polimerase Dirigida por RNA/metabolismo , Relação Estrutura-Atividade , Especificidade por Substrato , Nucleotídeos de Timina/síntese químicaRESUMO
The circular-dichroism and proton-magnetic-resonance spectra of complexes of ribonuclease A with dihydrouridine 3'-phosphate, 2'- and 3'-CMP, arabinosyl-3'-CMP, 1-(2-hydroxyethyl)cytosine 2'-phosphate and 1-(3-hydroxypropyl)cytosine 3'-phosphate were studied. Comparison of the results shows that non-additivity of the circular-dichroic spectrum of an enzyme-nucleotide complex may be due to: (a), alteration of the circular dichroic spectrum of the nucleotide under the influence of the asymmetric protein matrix (induced dichroism), and (b) a change in the nucleotide conformation. The contribution of each of the two factors was estimated to calculate the circular-dichoroic spectra of 2'-CMP and 3'-CMP in complex with ribonuclease A. 3'-CMP in this complex was characterized by negative circular dichroism in the long-wavelength absorption band of the nucleotide, whereas 2'-CMP was characterized by positive circular dichroism. Since both nucleotides in the complex are known to be in an anti conformation, it follows that even small changes in the conformation considerably modify the circular-dichroic spectrum of the nucleotide in complex with the enzyme.
