Lanthanide-based resonance energy transfer

Fluorescence resonance energy transfer is a powerful tool for studying nanometer-scale distances in biological macromolecules under physiological conditions. Using luminescent lanthanides instead of conventional fluorophores as donor molecules in energy transfer measurements offers many technical advantages and opens up a wide-range of new applications. Lanthanide photophysics and the instrumentation underlying these advantages are discussed. One new application, the study of conformational changes in the large protein complex actomyosin, which is responsible for muscle contraction and subcellular movement in many eucaryotes, is briefly discussed.