Metal complexes as tools for structural biology

Structural biologists currently have at their disposal a diverse and powerful range of tools and techniques that can be drawn upon to generate structural models. X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy provide high-resolution structures of proteins and nucleic acids with atomic level of detail. Within X-ray crystallographic studies, metal complexes have been employed for heavy-atom derivatization of proteins, enabling extraction of phase information, whilst NMR spectroscopic analysis of proteins and other macromolecules has benefited greatly from the introduction of so-called "lanthanide-binding tags". Selected luminescent lanthanide complexes have found application as "donors" in fluorescence resonance energy transfer (FRET) spectroscopic measurements, greatly extending the upper limit and accuracy of the distances that can be measured. A modification of conventional FRET that allows the measurement of longer distances with greater accuracy is luminescence resonance energy transfer (LRET).