Protein dynamics from single-molecule fluorescence intensity correlation functions.

Fluorescence intensity correlation functions contain information about photophysical and conformational dynamics. We propose and implement a simple procedure to analyze such functions measured in the presence of resonance energy transfer. When there is a separation of time scales and the conformational dynamics is modeled as diffusion in the potential of mean force along the interdye distance, we obtain an analytic expression for the conformational correlation time. This can be used to find the diffusion coefficient describing conformational fluctuations given the photon count rate and equilibrium distribution.