Bright lights, single molecules
The December issue of BioTechniques includes my TechNews feature on single-molecule FRET, “Bright lights, single molecules.” A technique for measuring the relative distance and orientation of two molecules relative to one another, smFRET has been likened to a “molecular ruler.” It has been used to study the folding of proteins of RNAs, the assembly of macromolecular complexes, and even drives an in-development “3rd-generation” sequencing technology called Project Starlight (Life Technologies).
As the name suggests, smFRET is a variant of FRET, a concept first detailed decades ago and as old as time: it is essentially thanks to FRET that light harvesting complexes in plant leaves can funnel their captured energy to photosynthetic centers. Yet traditional FRET describes the average behavior of a bulk population of molecules—the proverbial roar of the molecular crowd, as it were. smFRET focuses on individual molecules, recording energy transfer events as single molecules flex.
Taekjip Ha developed the technique as a graduate student with Shimon Weiss (then at UC Berkeley). The concluding statement in the abstract of his seminal paper, which his graduate research advisors insisted he include, reads: “Monitoring conformational changes, such as rotations and distance changes on a nanometer scale, within single biological macromolecules, may be possible with single-pair FRET.” “I thought that was bullshit,” Ha now recalls, “but it turned out they were right. It turned out to be a general mechanism to study biomolecular interactions.”
Biotechnically Speaking 