Fluorescence spectroscopic investigations of the dynamic properties of proteins, membranes and nucleic acids.

Fluorescence spectroscopy can reveal the dynamic properties of proteins, membranes and nucleic acids on the nanosecond timescale. Dynamic processes which can affect the fluorescence spectral characteristics of biopolymer-bound fluorophores include dipolar relaxation around excited state dipoles, rotational diffusion of fluorophores, and permeation of bipolymers of fluorescence quenchers. The occurrence of these processes is revealed by the time-dependence of the Stokes's shifts, the time dependence of fluorescence anisotropies and the quenching of fluorescence, respectively. We will describe each of these processes in detail using examples of data obtained for membrane-bound fluorophores. In addition, we will review the fluorescence spectral evidence for nanosecond structural fluctuations in proteins and nucleic acids. In total, fluorescence spectroscopy indicates that both proteins and membranes fluctuate rapidly on the nanosecond and subnanosecond timescale. In contrast, base pairs in double-helical DNA appear to be immobile on this timescale.