单分子的双光子激发光漂白速率

Photobleaching Rate Under Two-photon Excitation Microscopy at Single Molecule Level

研究了多种条件下的光漂白几率与激发光强度间的定量依赖关系。利用MRC1024多光子激发显微系统和单光子计数技术,测量了单个若丹明B(Rh B)分子在不同强度光激发时的双光子激发(TPE)和光漂白寿命。实验结果表明:单个RhB分子和TPE光漂白寿命与激发光强度倒数的平方成正比,亦即光漂白速率与荧光基团分子处于激发态的几率成线性依赖关系,该结果与单光子激发(1PE)时的光漂白结果相同,但是却不同于多分子TPE光漂白的实验结果。

The quantitative intensity dependence of photobleaching rate has become crucial in elucidating the photobleaching mechanism. The two-photon excitation （TPE） photobleaching lifetimes of single rhodamine B（Rh B） molecule excited by femtosecond pulse laser with different intensity were measured using the MRC1024 multi-photon excitation fluorescence microscopy system and the single-molecule counter. Experimental results show that the photobleaching lifetime of single RhB molecule with TPE depends on the two-power of the intensity of excitation laser, implying that the photobleaching rate depends linearly on the probability of single dye molecule in the excited states. The result is consistent with photobleaching results with one-photon excitation（1PE）,but is different from that of ensemble photobleaching with TPE.