New perspectives of fluorescence correlation spectroscopy

The principle of fluorescence correlation spectroscopy is outlined. The tec hnique has been applied to a mutant of the well-known green fluorescent pro tein. A comparative study has been made with time-resolved fluorescence ani sotropy. The latter experiment shows that the fluorophore is rigidly bound inside the protein matrix follows the rotation of the whole protein and doe s not show any fast restricted motion. It is evident from fluorescence corr elation spectroscopy that some excited state reaction plays a role, since t he autocorrelation traces show a significant effect on the incident laser p ower. Other potential applications of fluorescence correlation spectroscopy are presented as taken from very recent publications.