ABSTRACT
However, although single molecule spectroscopy techniques provide the ultimate resolution for molecular processes, they also su er from disadvantages. Single molecule observations are time consuming since one has to record many single molecule events to obtain good statistics and o en require complicated data evaluation procedures. One solution to this problem was invented by Madge et al. (Magde et a l., 1972) who introduced uorescence correlation spectroscopy (FCS), a te chnique with single molecule sensitivity but at the same time based on the fast statistical treatment of the recorded data. In FCS, the uorescence intensity from a very small observation volume (∼10−15 L) i s recorded with high temporal resolution. Any process that causes variations in the uorescence intensity and happens on a timescale slower than the recording speed of FCS will leave characteristic uctuations in the intensity trace. ese uctuations can be identi ed by either a Fourier transform or an autocorrelation analysis.
