title: Nanometre localization of single ReAsH molecules.
abstract: ReAsH is a red-emitting dye that binds to the unique sequence Cys-Cys-Xaa-Xaa-Cys-Cys (where Xaa is a noncysteine amino acid) in the protein. We attached a single ReAsH to a calmodulin with an inserted tetracysteine motif and immobilized individual calmodulins to a glass surface at low density. Total internal reflection fluorescence microscopy was used to image individual ReAsH molecules. We determined the centre of the distribution of photons in the image of a single molecule in order to determine the position of the dye within 5 nm precision and with an image integration time of 0.5 s. The photostability of ReAsH was also characterized and observation times ranging from several seconds to over a minute were observed. We found that 2-mercaptoethanesulphonic acid increased the number of collected photons from ReAsH molecules by a factor of two. Individual ReAsH molecules were then moved via a nanometric stage in 25 or 40 nm steps, either at a constant rate or at a Poisson-distributed rate. Individual steps were clearly seen, indicating that the observation of translational motion on this scale, which is relevant for many biomolecular motors, is possible with ReAsH.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA.
authors.forename: H
authors.initials: H
authors.lastname: Park
authors.forename: G T
authors.initials: GT
authors.lastname: Hanson
authors.forename: S R
authors.initials: SR
authors.lastname: Duff
authors.forename: P R
authors.initials: PR
authors.lastname: Selvin
mesh_terms: D000595:Amino Acid Sequence; D002147:Calmodulin / Q000737:chemistry / Q000648:ultrastructure*; D008856:Microscopy, Fluorescence / Q000379:methods; D008969:Molecular Sequence Data; D017785:Photons
chemical_list: D002147:Calmodulin