Time resolved multiphoton excited fluorescence probes in model membranes

Using the time-correlated single-photon counting technique, this thesis reports on a time-resolved fluorescence study of several fluorescent probes successfully employed in membrane research. Concentration and temperature effects on fluorescence anisotropy parameters are demonstrated by DPH, p-terphenyl, #alpha#-NPO and PPO in DPPC lipid bilayers. Fluorescence anisotropy has shown that trans-stilbene and Rhd 800 have a two-site location in membranes. Multiphoton induced fluorescence of DPH, p-terphenyl, #alpha#-NPO and v-biphenyl in liposomes was measured using 800nm excitation with a femtosecond Ti:Sapphire laser. P-terphenyl, #alpha#-NPO and v-biphenyl are new probes for membranes. Comparison of one and multiphoton excitation results has demonstrated higher initial anisotropy with multiphoton excitation than with one-photon excitation. The rotational times were identical for one and multiphoton excitation, indicating the absence of significant local heating or sample perturbation. Excimer formation of #alpha#-NPO was observed in DPPC liposomes with both one and multiphoton excitation. Phase transitions and phase separation are for the first time manifested by multiphoton induced fluorescence of DPH and p-terphenyl in binary liposomes of DPPS/DPPC, DMPC/DPPC and CH/DPPC mixtures. They are also confirmed by one-photon excitation. Time-resolved one and multiphoton induced fluorescence of DPH and p-terphenyl indicates that the two molecules have very similar behaviour in probing fluidity of model membranes. The multiphoton experiments for p-terphenyl were performed with a low concentration of 2x10"-"5M, proving p-terphenyl to be a promising membrane probe for three-photon excitation. Higher dynamic resolution and faster measurements can be potential advantages of multiphoton techniques applied to fluorescence probe studies of membranes. (author)Available from British Library Document Supply Centre- DSC:DXN055774 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo