Lateral Diffusion of Amphiphiles in Fatty Acid Monolayers at the Air-Water Interface: A Steady-State and Time-Resolved Fluorescence Quenching Study

Abstract

Lateral diffusion of amphiphilic molecules has been investigated in oleic acid (OA) monolayers at the air-water interface by studying the fluorescence quenching of N-(1-pyrenylsulfonyl)dipalmitoyl-l-α-phosphatidylethanolamine (pyrenyl-DPPE) by 4-(N,N-dimethyl-N-hexadecylammonium)-2,2,6,6-tetramethylpiperidine-1-oxyl iodide (CAT-16). Both steady-state and time-resolved techniques were employed to yield data which show clear evidence for the features predicted for diffusion-controlled reactions in two dimensions. Analysis of the steady-state quenching behavior as a function of quencher concentration produced nonlinear Stern-Volmer plots. The time-resolved measurements showed single-exponential..