Advances in single-molecule fluorescence methods for molecular biology.

Ever since their introduction two decades ago, single-molecule (SM) fluorescence methods have matured and branched out to address numerous biological questions, which were inaccessible via ensemble measurements. Among the current arsenal, SM fluorescence techniques have capabilities of probing the dynamic interactions of nucleic acids and proteins via Förster (fluorescence) resonance energy transfer (FRET), tracking single particles over microns of distances, and deciphering the rotational motion of multisubunit systems. In this exciting era of transitioning from in vitro to in vivo and in situ conditions, it is anticipated that SM fluorescence methodology will become a common tool of molecular biology.