Macromolecular models by single molecule FRET

Single molecule fluorescence energy transfer (FRET) experiments enable investigations of macromolecular conformation and folding by the introduction of fluorescent dyes at specific sites in the macromolecule. Multiple such experiments can be performed with different labeling site combinations in order to map complex conformational changes or interactions between multiple molecules. Distances that are derived from such experiments can be used for determination of the fluorophore positions by triangulation. When combined with a known structure of the macromolecule(s) to which the fluorophores are attached, a three-dimensional model of the system can be determined by docking calculations. Here we discuss recent applications of single molecule FRET to obtain a model of the synaptotagmin-1:SNARE complex and to study the conformation of PSD-95.