Fluorescence correlation spectroscopy (FCS)--a highly sensitive method to analyze drug/target interactions.

Fluorescence Correlation Spectroscopy (FCS) a new analytical technology, allows binding properties to be determined very accurately in biological assays at the level of single molecules. At concentrations of > or = 10(-12) M, binding constants, on/off-rates, and even reaction/enzyme kinetics can be determined in real-time, and in sample volumes as low as 10(-9) microliters. The FCS technology can be applied to study molecular and cellular interactions in homogeneous assays. Assay times in the range of seconds in combination with nanoliter sample volumes allow FCS to be used for high throughput screening to identify new pharmaceutical lead structures or new pharmacological targets. FCS is fully compatible with standard microtiter plate formats. However, for high throughput screening, specially designed sample carriers containing many thousand sub-microliter sample wells may be used in combination with a nanopipetting and sample retrieval system.