A new type of microscopy invented by Xiaowei Zhuang and colleagues at Harvard University and the Howard Hughes Medical Institute delivers spatial resolution more than 10 times better than that of conventional optical microscopes, putting scientists tantalizingly close to the first crisp, ultra-resolution, real-time imaging of living biomolecules and cells. Zhuang, along with Michael J. Rust and Mark Bates at Harvard, describes stochastic optical reconstruction microscopy, or STORM. They use fluorophores, glowing molecules that can be driven between a fluorescent and a dark state hundreds of times with repeated exposure to light with different colors.
Their solution, described this week in Nature Methods, is to only activate a small fraction of the fluorophores at a time, imaging them and determining their location to nanometer resolution.
Rust and Bates attached fluorophores to antibodies, which can be engineered to attach in turn to many types of biomolecules. Exposure of a fluorophore-bound biological sample to successive flashes of light of varying wavelengths activates different subsets of fluorophores, revealing their locations. After many such still images are taken, they are merged into a single image -- a sea of glowing fluorophores clearly resolvable, for instance, along a strand of DNA or protein filament.
The whole STORM imaging process currently takes several minutes to create a crisp imaging of a biological sample. They are fairly confident that we can ramp up the speed to virtually real-time. The next step is a molecular resolution, multi-color, real-time STORM for live object imaging.