Greenough Kelly P, Blanchard G J
Department of Chemistry, Michigan State University, East Lansing, Michigan 48824-1322, USA.
J Phys Chem B. 2006 Mar 30;110(12):6351-8. doi: 10.1021/jp057073v.
We report here on the motional and fluorescence lifetime dynamics of the chromophore NBDHA (6-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoic acid) in neat solvents and in aqueous solutions containing unilamellar vesicles of varying composition. We measure the transient response of this chromophore by time-correlated single-photon counting, using one- and two-photon excitation to resolve the Cartesian components of the rotational diffusion constant, D. Our experimental data for NBDHA in selected solvents of varying viscosity demonstrate that one- and two-photon excitation probe different components of the rotational diffusion constant and that this chromophore reorients as a prolate rotor with an aspect ratio of approximately 2. For NBDHA in aqueous solutions containing unilamellar vesicles of varying composition, we recover the same reorientation behavior regardless of vesicle composition. Fluorescence lifetime and steady-state fluorescence data show the chromophore to reside in a polar environment that is different from neat water. We understand these data in the context of the chromophore residing in close proximity to the unilamellar vesicle polar headgroups in all cases.
我们在此报告发色团NBDHA（6-（N-（7-硝基苯并-2-恶唑-1,3-二氮杂环丁烷-4-基）氨基）己酸）在纯溶剂以及含有不同组成的单层囊泡的水溶液中的运动和荧光寿命动力学。我们通过时间相关单光子计数测量该发色团的瞬态响应，使用单光子和双光子激发来解析旋转扩散常数D的笛卡尔分量。我们在选定的不同粘度溶剂中对NBDHA的实验数据表明，单光子和双光子激发探测旋转扩散常数的不同分量，并且该发色团作为长轴比约为2的长椭球转子重新取向。对于含有不同组成单层囊泡的NBDHA水溶液，无论囊泡组成如何，我们都能得到相同的重新取向行为。荧光寿命和稳态荧光数据表明发色团存在于与纯水不同的极性环境中。在所有情况下，我们认为这些数据是由于发色团紧邻单层囊泡的极性头部基团。
