PHOTOCHEMISTRY AND FLUORESCENCE EMISSION DYNAMICS OF SINGLE MOLECULESIN SOLUTION - B-PHYCOERYTHRIN

We report the first detailed studies of the photochemistry of single m olecules in aqueous solution. Photolysis of single B-phycoerythrin (B- PE) molecules, a highly fluorescent phycobiliprotein containing 34 bil in chromophores, is observed as an abrupt cessation of the fluorescenc e emission from individual molecules as they flow through a similar to 40 pL probe volume. These measurements demonstrate that B-PE is photo lyzed in a single photochemical step. The observation of abrupt photob leaching of single molecules could not be made in a bulk measurement b ecause the signal would be averaged over many molecules to yield a con tinuous decay. Photon pair correlation measurements of the fluorescenc e detected from single B-PE molecules demonstrate that the molecule be haves as a single quantum system, not as a collection of 34 independen t chromophores.