title: Differential evanescence nanometry: live-cell fluorescence measurements with 10-nm axial resolution on the plasma membrane.
abstract: We present a method to resolve components within a diffraction-limited object by tracking simultaneously the average axial positions of two different sets of fluorescent molecules within it. The axial positions are then subtracted from each other to determine the separation of the two sets of fluorophores. This method follows the dynamic changes in the separation of the two sets of fluorophores with freely rotating dipoles using sequential acquisitions with total internal reflection and wide-field illumination, and it can be used to measure the formation of small structures on living cells. We have verified that we can achieve a resolution of 10 nm, and we have used the method to follow the location of clathrin and its adaptor AP-2 as they are recruited to a diffraction-limited coated pit during its assembly at the plasma membrane. We find a gradually increasing axial separation between the centroids of clathrin and AP-2 distribution, up to a final value of 30 nm just before coated-pit pinching and formation of the coated vesicle.
authors.affiliation: Department of Cell Biology and Immune Disease Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Saveez
authors.initials: S
authors.lastname: Saffarian
authors.forename: Tomas
authors.initials: T
authors.lastname: Kirchhausen
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002138:Calibration; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism*; D002966:Clathrin / Q000737:chemistry; D020285:Cryoelectron Microscopy / Q000379:methods; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry; D008856:Microscopy, Fluorescence / Q000295:instrumentation / Q000379:methods*; D015233:Models, Statistical; D009010:Monte Carlo Method; D015203:Reproducibility of Results; D013816:Thermodynamics; D013997:Time Factors
chemical_list: D002966:Clathrin; D005456:Fluorescent Dyes