Estrutura eletronica das melaninas
AUTOR(ES)
Douglas Soares Galvão
DATA DE PUBLICAÇÃO
1989
RESUMO
Melanin?s form a class of biological pigments which presents photoprotection as its basic function and amorphous semiconductor features. Though the structure and composition of these pigments are not well characterized, there is no doubt 5,6,indolquinone (lQ) is the most important monomer related to them. In this work we have studied the electronic structure of the melanin?s, based on models of IQ polymers. We have used Hückel Theory (HT) to investigate the electronic properties of finite and infinite (in Bloch s limit), ordered and disordered, polymeric chains. Data obtained from the utilization of more sophisticated methods (MNDO and INDO) for IQ monomers and dimmers are in good agreement with the conclusions we had drawn from HT calculations. The model we present here for the electronic structure of melanin?s is able to explain the major part of available experimental data about this material (paramagnetism, optical properties, etc.); it also seems to confirm the hypothesis of the existence of a cellular defense mechanism, based or the electronic capture of (potentially citotoxic) free radicals
