S E M I N A R FLUORESCENCE BLINKING IN FLUOROPHORES MONITORED BY FLUORESCENCE CORRELATION SPECTROSCOPY Jerker Widengren Exp. Biomol. Physics / Applied Physics, Royal Inst. Technology (KTH) Stockholm, Sweden Utorak, 4 septembar, 2012 g. u 14 h u Biblioteci Instituta Abstract In FCS there are many ways by which molecular dynamic processes can be monitored. One useful strategy is to analyse fluorescence fluctuations arising due to a dynamic process taking place, which switches the fluorescence of the studied molecules on and off. In this presentation it will be discussed how FCS can be used to extract information from molecular dynamic processes that change the fluorescence brightness of the analysed molecules. It will be shown how FCS in combination with ion sensitive fluorophores allow direct monitoring of ion exchange at a molecular level, at equilibrium, with no perturbations, and with negligible buffer effects from the fluorophores themselves. Further, it is shown how FCS offers a straightforward means to monitor the population kinetics of photo-induced, non-fluorescent transient states of fluorophores. Knowledge about the population kinetics of these states is important for the optimization of the fluorescence signal in single molecule experiments, but can also provide complementary dimensions of fluorescence-based information.