Comments on fluorescence methods for probing local deviations from lamellar packing.

Fluorescence probes have been used to monitor the conversion from the lamellar to nonlamellar phases. In addition there is current interest in understanding the nature of the changes in the physical properties of phospholipid bilayers that are correlated with their propensity for forming nonlamellar phases. Fluorescent probes have been used to demonstrate changes in surface hydrophobicity, quenching efficiency, and rates of interbilayer transfer of fluorescently labeled analogs. These studies are beginning to provide an assessment of the nature of the differences between stable bilayers and those that readily convert into inverted phases. Such studies are important because these differences in physical properties often lead to altered membrane functional behavior.