Caruso F, Grieser F, Thistlethwaite P J, Almgren M
School of Chemistry, University of Melbourne, Parkville, Australia.
Biophys J. 1993 Dec;65(6):2493-503. doi: 10.1016/S0006-3495(93)81301-8.
Steady-state and time-resolved fluorescence spectroscopy has been used to examine lateral diffusion in dipalmitoyl-L-alpha-phosphatidylcholine (DPPC) and dimyristoyl-L-alpha-phosphatidylcholine (DMPC) monolayers at the air-water interface, by studying the fluorescence quenching of a pyrene-labeled phospholipid (pyrene-DPPE) by two amphiphilic quenchers. Steady-state fluorescence measurements revealed pyrene-DPPE to be homogeneously distributed in the DMPC lipid matrix for all measured surface pressures and only in the liquid-expanded (LE) phase of the DPPC monolayer. Time-resolved fluorescence decays for pyrene-DPPE in DMPC and DPPC (LE phase) in the absence of quencher were best described by a single-exponential function, also suggesting a homogeneous distribution of pyrene-DPPE within the monolayer films. Addition of quencher to the monolayer film produced nonexponential decay behavior, which is adequately described by the continuum theory of diffusion-controlled quenching in a two-dimensional environment. Steady-state fluorescence measurements yielded lateral diffusion coefficients significantly larger than those obtained from time-resolved data. The difference in these values was ascribed to the influence of static quenching in the case of the steady-state measurements. The lateral diffusion coefficients obtained in the DMPC monolayers were found to decrease with increasing surface pressure, reflecting a decrease in monolayer fluidity with compression.
稳态和时间分辨荧光光谱已被用于通过研究芘标记的磷脂（芘 - 二棕榈酰磷脂酰乙醇胺，pyrene-DPPE）被两种两亲性猝灭剂的荧光猝灭，来检测空气 - 水界面处二棕榈酰 - L-α - 磷脂酰胆碱（DPPC）和二肉豆蔻酰 - L-α - 磷脂酰胆碱（DMPC）单层中的横向扩散。稳态荧光测量表明，对于所有测量的表面压力，芘 - DPPE在DMPC脂质基质中均匀分布，并且仅在DPPC单层的液晶扩展（LE）相中均匀分布。在没有猝灭剂的情况下，DMPC和DPPC（LE相）中芘 - DPPE的时间分辨荧光衰减最好用单指数函数来描述，这也表明芘 - DPPE在单层膜内均匀分布。向单层膜中添加猝灭剂会产生非指数衰减行为，这可以用二维环境中扩散控制猝灭的连续介质理论来充分描述。稳态荧光测量得到的横向扩散系数明显大于从时间分辨数据获得的扩散系数。这些值的差异归因于稳态测量情况下静态猝灭的影响。发现在DMPC单层中获得的横向扩散系数随着表面压力的增加而降低，这反映了随着压缩单层流动性的降低。
