Analysis of Ligand-Receptor Interaction on the Surface of Living Cells by Fluorescence Correlation Spectroscopy~!2009-12-01~!2010-02-22~!2010-04-23~!

Ligand-receptor interaction on the cell surface has traditionally been analyzed by using radioisotope-labeled ligands.The reaction is carried out at low temperatures such as 4 o C or on ice in order to prevent endocytosis of the ligandreceptor complex, followed by extensive washing to remove unbound ligands from cells.To overcome these drawbacks, in the present study we have employed fluorescence correlation spectroscopy (FCS) with single-molecule sensitivity for the analysis of the interaction of epidermal growth factor (EGF) with its receptor, EGFR, on the surface of living cells, and have successfully determined their dissociation constants.Moreover, FCS has also been used to determine the diffusion coefficient of EGFR in the membrane as well as to quantify the number of EGFR molecules expressed on the cell surface.