title: Damage-free vibrational spectroscopy of biological materials in the electron microscope.
abstract: Vibrational spectroscopy in the electron microscope would be transformative in the study of biological samples, provided that radiation damage could be prevented. However, electron beams typically create high-energy excitations that severely accelerate sample degradation. Here this major difficulty is overcome using an 'aloof' electron beam, positioned tens of nanometres away from the sample: high-energy excitations are suppressed, while vibrational modes of energies <1 eV can be 'safely' investigated. To demonstrate the potential of aloof spectroscopy, we record electron energy loss spectra from biogenic guanine crystals in their native state, resolving their characteristic C-H, N-H and C=O vibrational signatures with no observable radiation damage. The technique opens up the possibility of non-damaging compositional analyses of organic functional groups, including non-crystalline biological materials, at a spatial resolution of ∼10 nm, simultaneously combined with imaging in the electron microscope.
authors.affiliation: Department of Physics, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Rez
authors.affiliation: LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Aoki
authors.affiliation: Laboratoire de Physique des Solides, Université Paris-Sud, CNRS, UMR8502, Orsay 91405, France.
authors.forename: Katia
authors.initials: K
authors.lastname: March
authors.affiliation: Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Dvir
authors.initials: D
authors.lastname: Gur
authors.affiliation: Department of Physics, Arizona State University, Tempe, Arizona 85287, USA.|Nion Co., 11511 NE 118th St., Kirkland, Washington 98034, USA.
authors.forename: Ondrej L
authors.initials: OL
authors.lastname: Krivanek
authors.affiliation: Nion Co., 11511 NE 118th St., Kirkland, Washington 98034, USA.
authors.forename: Niklas
authors.initials: N
authors.lastname: Dellby
authors.affiliation: Nion Co., 11511 NE 118th St., Kirkland, Washington 98034, USA.
authors.forename: Tracy C
authors.initials: TC
authors.lastname: Lovejoy
authors.affiliation: Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Sharon G
authors.identifier: http://orcid.org/0000-0002-5337-5063
authors.initials: SG
authors.lastname: Wolf
authors.affiliation: Department of Chemical Research Support, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Hagai
authors.initials: H
authors.lastname: Cohen
mesh_terms: D000818:Animals; D002347:Carps; D006147:Guanine / Q000737:chemistry*; D008854:Microscopy, Electron / Q000295:instrumentation; D046529:Microscopy, Electron, Transmission / Q000295:instrumentation*; D046590:Spectroscopy, Electron Energy-Loss / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods*; D013057:Spectrum Analysis / Q000379:methods; D014732:Vibration
chemical_list: D006147:Guanine