Bridging conformational dynamics and function using single-molecule spectroscopy.

In a typical structure-function relation study, the primary structure of proteins or nucleic acids is changed by mutagenesis and its functional effect is measured via biochemical means. Single-molecule spectroscopy has begun to give a whole new meaning to the "structure-function relation" by measuring the real-time conformational changes of individual biological macromolecules while they are functioning. This review discusses a few recent examples: untangling internal chemistry and conformational dynamics of a ribozyme, branch migration landscape of a Holliday junction at a single-step resolution, tRNA selection and dynamics in a ribosome, repetitive shuttling and snapback of a helicase, and discrete rotation of an ATP synthase.