EFFECTS OF MOLECULAR-ORGANIZATION ON PHOTOPHYSICAL AND PHOTOCHEMICAL BEHAVIOR - INTERACTIONS OF OXYGEN AND PYRENE-BEARING PROBES ACROSS THE AIR LIPID BOUNDARY IN SPREAD MONOLAYERS

Oxygen quenching of excited singlet pyrene probes in spread monolayers of dioleoylphosphatidylcholine (DOL), dipalmitylphosphatidylcholine (DPL), and dielaidylphosphatidylcholine (DEL), has been measured by time-resolved fluorescence. The probes used were a pyrene-bearing phosphatidylcholine (2-PyPC) and 1-pyrenedodecanoic acid (Py-22). In all cases, oxygen quenching was diminished by compression of the monolayer system. Plots of k(q), the pseudo-first-order rate constant for quenching of Py-22* by oxygen, vs area per lipid molecule in the layer approached linearity more nearly than those involving 2-PyPC. This behavior may arise from the greater freedom of movement associated with Py-22. In all cases involving DPL, the phase transition behavior of the lipid introduced irregularities into the plot of area/molecule vs quenching rate constant.