Transferencia de energia em sistemas modelo de membranas

Following brief reviews on energy transfer (E T), and lipid vesicles as bio membrane models, E T studies (together with other photophysical methodologies) in several lipidic systems are described. For each system, adequate donor and acceptor probes were used. The formalism used for investigating the probe distribution in dipalmitoyl phosphatidylcholine vesicles (gel and fluid phases) is described. From analysis of donor fluorescence decays, it is concluded that probes that are randomly distributed in the fluid aggregate in the gel. These results were rationalized on the basis of probe segregation into defects in this phase. Studies in two-phase two-component systems are described, with both gel / fluid (dilauroyl phosphatidylcholine / distearoyl phosphatidylcholine) and fluid / fluid (dimirystoylphosphatidylcholine / cholesterol) phase coexistence. Information about distribution of probes in these systems and micro domain size (<20 nm for the liquid ordered phase in dimirystoylphosphatidylcholine / cholesterol) was obtained. Finally, biological molecules (the fluorescent sterol dehydroergosterol and the antibiotic filipin) in dipalmitoyl phosphatidylcholine are studied, with emphasis on the aggregation state of these molecules, in relation to their role in bio membranes. This work illustrates the applicability of E T in the study of micro heterogeneity in model membranes, from which one can obtain conclusions relevant for bio membranesAvailable from Fundacao para a Ciencia e a Tecnologia, Servico de Informacao e Documentacao, Av. D. Carlos I, 126, 1249-074 Lisboa, Portugal / FCT - Fundação para o Ciência e a TecnologiaSIGLEPTPortuga