Site specific multi-point fluorescence measurement system for fluorescence correlation spectroscopy

Multi point fluorescence measurement system using basic image shifting method and commercial multi mode fiber is presented in this paper. Using a singlet lens, the original fluorescence image of a sample is shifted to another plane which can be monitored using ccd, and at the first image plane independent two fiber tips in an xyz stage deliver each fluorescent signal at a specific sample position to a fluorescence correlation spectroscopy (FCS) with an electron multiplying charge coupled device (EMCCD). The FCS is composed with an EMCCD, which can detect single molecule level fluorescence light. Applying region of interest (ROI) and pixel binning, a time resolution of up to 2 ms can be achieved, which is sufficient to resolve the diffusion of fluorescence micro-sphere in solution. The advantages of implementing EMCCD cameras in wide-field ultra low light imaging, as well as in site-specific multi-point fluorescence measurement system, can consequently also be exploited for spatially and spectrally resolved FCS. Experimental results about FCS with spectrum informations demonstrate the advantage of the simplicity and flexibility of our system. We expect that this multi point measurement system also can be applied to other study of bio molecular dynamics.