Submicrosecond real-time fluorescence sampling: application to protein folding.

Time-resolved fluorescence detection has become a central tool in the study of protein folding. This article briefly reviews modern fluorescence techniques and then focuses on recent improvements made possible by array photomultipliers, computer-controlled data gating, and long-memory multi-channel digitizers. It is now possible to detect fluorescence wavelength profiles and/or fluorescence decay transients very cost effectively with sub-microsecond kinetic time resolution out to long times. Folding kinetics can be analyzed by singular value decomposition (SVD) or chi-analysis. The latter provides an objective method for detecting nonexponential kinetics in two-state systems.