Nano science

William E. Moerner (N)
Stanford University (USA)

Light and Single Molecules Open a New Window Into the Nanoscale and Biomolecular Dynamics

More than 25 years ago, low-temperature experiments aimed at establishing the ultimate limits to optical storage in solids led to the first optical detection and spectroscopy of a single molecule in the condensed phase. At this unexplored ultimate limit, many surprises occurred such as spectral diffusion/blinking and light-driven control of emission. The years of work on single molecules at room temperature led to a huge array of further advances by many researchers worldwide, including the surprising observation of blinking and switching of single green fluorescent protein variants. In 2006, PALM and related approaches showed that the optical diffraction limit of ~200 nm can be circumvented with single molecules to achieve super-resolution (SR) fluorescence microscopy. Essential to this is the combination of single-molecule imaging with active control of the emitting concentration and sequential localization of single fluorescent labels. SR microscopy has opened up a new frontier in which biological structures and behavior can be observed with resolutions down to 20-40 nm and below, and critical work continues to address optical and chemical challenges.