Abstract: We report an investigation on the surface behaviors, including diffusion, desorption and fluorescence blinking, of rhodamine-labeled phospholipid molecules at single-molecule level by confocal fluorescence microscopy. It was found that besides an average force field on the hydrophilic glass surface there exist special sites that strongly adsorb rhodamine-labeled phospholipid molecules. The desorption rate of the strongly adsorbed molecules is determined to be (5.9±0.2) s－1. The diffusion coefficient of the molecules on the surface, (3.3±0.1)×10－8 cm2•s－1, is much smaller than that in aqueous solution, (2.3±0.1)×10－6 cm2•s－1, but is in the same order as that in a fluid phospholipid membrane. Fluorescence blinking was observed in some of the strongly adsorbed molecules, which may be attributed to reversible quantum jumps to dark states induced by the strong interaction between the molecule and adsorption sites.

Key words: Single molecule detection, Phospholipid, Confocal fluorescence microscopy, Fluorescence blinking