Obten??o das conforma??es mais est?veis da mol?cula de ?-naftilxilose

• Ano de defesa: 2015
• Autor(a) principal: Goulart, Paula do Nascimento
• Orientador(a): Silva, Clarissa Oliveira da
• Banca de defesa: Barbosa, Andre Gustavo Horta, Pereira, Marcio Soares
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal Rural do Rio de Janeiro
• Programa de Pós-Graduação: Programa de P?s-Gradua??o em Qu?mica
• Departamento: Instituto de Ci?ncias Exatas
• País: Brasil
• Palavras-chave em Português: ?-naftilxilose; conforma??o de carboidratos; rota??o espec?fica
• Palavras-chave em Inglês: ?-naphthylxylopiranose; carbohydrate conformation; specific rotation
• Área do conhecimento CNPq: Qu?mica
• Link de acesso: https://tede.ufrrj.br/jspui/handle/jspui/4161

Carbohydrates are the most abundant class of compounds in nature, performing several different biological and metabolic functions, besides several industrial applications. The existence of many hydroxyl groups that may interact in different orientations allows different conformational possibilities to be investigated. Data obtained for xylose indicate that this pentose with an hydrophobic substituent, is able to promote a bonding (it acts as a primer of a sequence of four tetrasaccharides) between the glycosaminglycans and the extracellular proteins in tumor cells. This attachment contributes considerably to the decrease of proliferation and nutrition of tumor cells, acting on a selective way. The objective of this work is to identify the most stable conformations of the molecule of ?-naphthylxylose, and from these results to better understand the nature of the interaction between carbohydrate and protein in future works. Firstly, it is necessary to perform a conformational study in the gas phase, in solution (PCM) and expliciting a solvent molecule from the bulk, including optimization geometry calculations, frequency, population and specific rotation calculations. For these calculations, Density Functional Theory (DFT) will be used with a 6-31+G(d,p) basis functions, that was proven to be suited for the treatment of large size carbohydrates. The number of conformers to be investigated for this system is determined by the several positions that each of the three hydroxyl group in the molecule can assume individually, besides the orientation of the naphtyl group. Initially, considering the dihedral ?1, ?2, ?3 and ?4, respectively defined by the sequence of atoms (C?naftil-C1-O1-O5), (H2 O2 C2-C1), (C3 H3 O3-C2) and (-H4 O4 C3 -C4) geometry optimization calculations were performed in the gas phase for 81 conformational possibilities. Combining the six values of dihedral angle found for the ?naftil group orienattio (C?naftil C?naftil-C1-O1-) - obtained from the construction of potential energy surface, with the twelve most stable conformations found in the first part of this study, seventy two possibilities to be investigated were generated, from which was obtained fifty-one conformations after geometry optimization calculations. For the nineteen most stable conformations, were performed calculations in solution (PCM) as well as expliciting one molecule of the solvent from the bulk solution. New geometry optimization, frequency and specific rotation calculations were performed. For the system solvated in PCM, the value of specific rotation was found as -70.12 ? / dm (g / cm3) and for the microsolvated system the value found for this property was -42.82 ? / (dm (g / cm 3). Comparing these values, it is possible to observe that the latter is closest to that experimental value, which is -32 ? / (dm (g / cm3).