Intramolecular excimer fluorescence kinetics of 1,2-bis(4-pyrenylbutanoyl)phosphatidylcholine as a probe of molecular organization in spread monolayers at the nitrogen-water interface

Intramolecular excimer kinetics in a lipid containing two pyrene moieties, 1,2-bis(4-pyrenylbutanoyl)-phosphatidylcholine, have been examined by steady-state and time-resolved fluorescence in spread monolayers of several lipids to determine the effects of molecular organization on lipid dynamics. It is found that excimer formation responds markedly to compression in monolayers of unsaturated lipids, such as dioleoylphosphatidylcholine (DOL) and dielaidoylphosphatidylcholine (DEL). As expected, excimer decay was found to be little affected by lipid packing. For dipalmitoylphosphatidylcholine (DPL) systems, discontinuous changes in photophysical behavior are seen at the lipid phase transition. These types of behavior are consistent with those observed for dipyrenyl compounds in vesicles and lend themselves to a parallel data treatment. The kinetics of this probe were also measured in bulk solutions of known viscosity to provide some comparison with the data found in monolayers. 10 refs., 8 figs.