title: Motion capture and manipulation of a single synthetic molecular rotor by optical microscopy.
abstract: Single-molecule imaging and manipulation with optical microscopy have become essential methods for studying biomolecular machines; however, only few efforts have been directed towards synthetic molecular machines. Single-molecule optical microscopy was now applied to a synthetic molecular rotor, a double-decker porphyrin (DD). By attaching a magnetic bead (ca. 200 nm) to the DD, its rotational dynamics were captured with a time resolution of 0.5 ms. DD showed rotational diffusion with 90° steps, which is consistent with its four-fold structural symmetry. Kinetic analysis revealed the first-order kinetics of the 90° step with a rate constant of 2.8 s(-1). The barrier height of the rotational potential was estimated to be greater than 7.4 kJ mol(-1) at 298 K. The DD was also forcibly rotated with magnetic tweezers, and again, four stable pausing angles that are separated by 90° were observed. These results demonstrate the potency of single-molecule optical microscopy for the elucidation of elementary properties of synthetic molecular machines.
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656 (Japan).
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Ikeda
authors.forename: Takahiro
authors.initials: T
authors.lastname: Tsukahara
authors.forename: Ryota
authors.initials: R
authors.lastname: Iino
authors.forename: Masayuki
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Noji
mesh_terms: D007700:Kinetics; D060526:Magnetic Fields; D008856:Microscopy, Fluorescence; D057054:Molecular Imaging; D009038:Motion; D009068:Movement; D052898:Optical Tweezers; D009942:Organometallic Compounds / Q000737:chemistry*; D011166:Porphyrins / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D011166:Porphyrins
keywords: molecular dynamics; molecular machines; optical microscopy; porphyrins; single-molecule studies