FCS- Fluorescence Correlation Spectroscopy

Fluorescence Correlation Spectroscopy (FCS) is a tool that provides quantitative localized measurements of important physical parameters including mechanisms of transport, molecular mobilities, and densities of fluorescently labeled species. In the most basic configuration, FCS examines the inherent correlations exhibited by the fluctuating fluorescent signal from labeled molecules as they transition into and out of a specified excitation volume or area. The dual-color variation, termed Fluorescence Cross-Correlation Spectroscopy (FCCS), is utilized to probe two species labeled with different fluorophores. FCCS can extend investigations to the examination of biochemical reactions between two partners, such as reaction rates, kinetics, fractions of binding or reacting molecules, and mobilities of a complex formed between the partners.