Collective effects in individual oligomers of the red fluorescent coral protein DsRed

We report on single-molecule experiments that were performed on two biologi cal systems, the recently cloned red fluorescent protein of a coral of the Discosoma genus (DsRed) and the enhanced green fluorescent protein, both of which were immobilized in polyvinylalcohol. Fluorescence intensity traject ories were recorded and compared to those of a reference compound, the orga nic dye hexaphenylbenzene perylenemonoimide. Evidence was found for the pre sence of DsRed as an oligomer even at subnanomolar concentrations. Both pro teins show triplet blinking in the millisecond time range. Collective effec ts could be observed for the Dsred oligomers. (C) 2001 Elsevier Science B.V . All rights reserved.