Microsecond dynamics of biological macromolecules

Abstract

Publisher Summary This chapter discusses that fluorescence spectroscopy is widely used to study the nanosecond timescale dynamics of biological macromolecules. The spectral observables are sensitive to nanosecond dynamics because emission also occurs on the nanosecond time scale. While nanosecond biopolymers dynamics are important, these rapid processes reflect mostly local fluorophore motions and its interactions with the immediate environment. However, biological macromolecules also display structural changes on the microsecond time scale. Processes that occur on the microsecond time scale include domain flexing in proteins and lateral diffusion in membranes. It is also likely that nucleic acid junctions and structured RNAs display microsecond motions. It discusses that fluorescence is now capable of detecting microsecond dynamics. This change in time scale is made possible by the development of metal-ligand complexes (MLCs), which display decay times ranging from 10 nsec to more than 10/μsec. The MLCs display several spectral characteristics that make them useful probes, including high photostability, a large Stokes shift, and polarized emission. The chapter presents data and simulations showing the possibility of measuring protein domain flexing, lateral diffusion in membranes, and microsecond rotational correlation times. Fluorescence is no longer trapped on the nanosecond time scale, and can be used to quantify dynamic processes from nanoseconds to microseconds to milliseconds because the lanthanides display millisecond decay times.