Sunday, August 22, 2010
Getting around the diffraction limit
Optical microscopy has been extensively used to observe biological processes, where counting and identifying of molecular structures are achieved for accurate measurements. To date, several promising technologies have been introduced to break the resolution limits of conventional microscopes (i.e diffraction limit ~200nm), including PALM,STORM and STED. These methods are called super-resolution techniques,where resolution is defined as the minimum distance or volume that can be measured between two identical particles in a given period of time. Since biological molecules are <5-10nm,getting molecular details requires imaging at this scale, which can be achieved by super-resolution methods. Another important method to break the diffraction limit is localization accuracy, where it's defined as the minimum distance or volume that one can locate a particle's position within a certain time period.Localization have paved the way to understand how some biological molecules move or change its position, including the motor protein analysis.
Simply, one should not confuse localization super-accuracy with super-resolution as aforementioned. Recently, Toprak et al. reviewed some of the methods that were used for both localization and super-resolution in fluorescence microscopy. Here is the article for further details:
Erdal Toprak, Comert Kural, Paul R. Selvin, "Super-accuracy and super-resolution getting around the diffraction limit," Methods in Enzymology 475:1-26 (2010).