罗丹明标记的磷脂分子在亲水表面的单个分子行为

单个分子实验有很重要的意义,一方面，对于非均相体系，单个分子实验可得到分子性质分布信息；另一方面，对于均相和非均相体系，单个分子轨迹直接记录了分子性质的涨落，包含了丰富的动力学信息.在诸多单个分子检测技术中，单分子光学检测技术具有快速、无损、可探测到凝聚相内部单个分子的能力.进行单分子检测的关键是消除拉曼和瑞利散射以及杂质荧光等背景的干扰，利用共焦、近场和隐失场激发减少激发体积和检测体积，可以降低背底，提高信噪比.本实验利用共焦荧光显微镜观测单个罗丹明标记的磷脂分子在亲水玻璃表面的扩散、脱附，及其荧光闪烁的行为.实验表明，除由表面的平均力场阻碍分子运动外，还有一些特殊位点会造成长时间的特异性吸附，并得到特异性吸附的分子的脱附速率，（5.9±0.2）s－1.用穿越时间分布函数测得分子在表面的扩散速率为(3.3±0.1)×10－8 cm2•s－1，与分子在磷脂膜中的扩散速率相当.观测到了一些吸附的分子出现了荧光闪烁的现象，并对其产生原因进行了一些分析.

Single-molecule Behavior of Rhodamine-labeled Phospholipid on a Hydrophilic Glass Surface

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 which 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.