Chattopadhyay Amitabha
Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India.
Chem Phys Lipids. 2003 Jan;122(1-2):3-17. doi: 10.1016/s0009-3084(02)00174-3.
Wavelength-selective fluorescence comprises a set of approaches based on the red edge effect in fluorescence spectroscopy which can be used to directly monitor the environment and dynamics around a fluorophore in a complex biological system. A shift in the wavelength of maximum fluorescence emission toward higher wavelengths, caused by a shift in the excitation wavelength toward the red edge of absorption band, is termed red edge excitation shift (REES). This effect is mostly observed with polar fluorophores in motionally restricted media such as very viscous solutions or condensed phases where the dipolar relaxation time for the solvent shell around a fluorophore is comparable to or longer than its fluorescence lifetime. REES arises from slow rates of solvent relaxation (reorientation) around an excited state fluorophore which is a function of the motional restriction imposed on the solvent molecules in the immediate vicinity of the fluorophore. Utilizing this approach, it becomes possible to probe the mobility parameters of the environment itself (which is represented by the relaxing solvent molecules) using the fluorophore merely as a reporter group. Further, since the ubiquitous solvent for biological systems is water, the information obtained in such cases will come from the otherwise 'optically silent' water molecules. This makes REES and related techniques extremely useful since hydration plays a crucial modulatory role in a large number of important cellular events, including lipid-protein interactions and ion transport. The interfacial region in membranes, characterized by unique motional and dielectric characteristics, represents an appropriate environment for displaying wavelength-selective fluorescence effects. The application of REES and related techniques (wavelength-selective fluorescence approach) as a powerful tool to monitor the organization and dynamics of probes and peptides bound to membranes, micelles, and reverse micelles is discussed.
波长选择性荧光包括一组基于荧光光谱中红边效应的方法，可用于直接监测复杂生物系统中荧光团周围的环境和动力学。由于激发波长向吸收带的红边移动而导致最大荧光发射波长向更高波长的移动，被称为红边激发位移（REES）。这种效应主要在运动受限介质中的极性荧光团中观察到，如非常粘稠的溶液或凝聚相，其中荧光团周围溶剂壳的偶极弛豫时间与其荧光寿命相当或更长。REES源于激发态荧光团周围溶剂弛豫（重新取向）的缓慢速率，这是荧光团附近溶剂分子所受运动限制的函数。利用这种方法，仅将荧光团用作报告基团就有可能探测环境本身的迁移率参数（由弛豫的溶剂分子表示）。此外，由于生物系统中普遍存在的溶剂是水，在这种情况下获得的信息将来自原本“光学沉默”的水分子。这使得REES及相关技术极其有用，因为水合作用在大量重要的细胞事件中起着关键的调节作用，包括脂质 - 蛋白质相互作用和离子运输。膜中的界面区域具有独特的运动和介电特性，是显示波长选择性荧光效应的合适环境。本文讨论了将REES及相关技术（波长选择性荧光方法）作为监测与膜、胶束和反胶束结合的探针和肽的组织和动力学的强大工具的应用。
