Real-time measurements of protein affinities on membrane surfaces by fluorescence spectroscopy.

Signal transduction in cells involves transitory interactions between proteins and membranes and between different proteins of the interacting species. These associations depend on the strength of the interactions and on the local concentration. Because the energy and intensity of the fluorescence of many probes are very sensitive to the local environment, fluorescence measurements can report on events, such as membrane binding and protein association, in real time. We describe methods to monitor associations both in vitro and in vivo by fluorescence.