The standard diffraction limit of light is about 250 nm, meaning that you cannot "resolve" objects closer than this distance. Despite this, we have come up with a method to measure 1.5 nm in x-y plane, with 1-500 msec, using a technique we call Fluorescence imaging with one-nanometer accuracy (FIONA) is a technique for localization a single dye, or a single group of dyes, to within approximately 1-nm accuracy. This high degree of precision is achieved using total internal reflection fluorescence microscopy, deoxygenation agents, and a high quantum yield, low-noise detector.
"In Vitro and in Vivo FIONA and other Acronyms for Watching Molecular Motors Walk", Paul R. Selvin, Tyler Lougheed, Melinda Tonks Hoffman, Hyokeun Park, Hamza Balci, Benjamin H. Belehm, and Erdal Toprak , Biophysics Center and Physics Department, University of Illinois, Urbana, Illinois 61801
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