title: Superb resolution and contrast of transmission electron microscopy images of unstained biological samples on graphene-coated grids.
abstract: BACKGROUND
  In standard transmission electron microscopy (TEM), biological samples are supported on carbon films of nanometer thickness. Due to the similar electron scattering of protein samples and graphite supports, high quality images with structural details are obtained primarily by staining with heavy metals.
  
  
  METHODS
  Single-layered graphene is used to support the protein self-assemblies of different molecular weights for qualitative and quantitative characterizations.
  
  
  RESULTS
  We show unprecedented high resolution and contrast images of unstained samples on graphene on a low-end TEM. We show for the first time that the resolution and contrast of TEM images of unstained biological samples with high packing density in their native states supported on graphene can be comparable or superior to uranyl acetate-stained TEM images.
  
  
  CONCLUSIONS
  Our results demonstrate a novel technique for TEM structural characterization to circumvent the potential artifacts caused by staining agents without sacrificing image resolution or contrast, and eliminate the need for toxic metals. Moreover, this technique better preserves sample integrity for quantitative characterization by dark-field imaging with reduced beam damage.
  
  
  CONCLUSIONS
  This technique can be an effective alternative for bright-field qualitative characterization of biological samples with high packing density and those not amenable to the standard negative staining technique, in addition to providing high quality dark-field unstained images at reduced radiation damage to determine quantitative structural information of biological samples.
authors.affiliation: Department of Physics, University of Central Florida, Orlando, FL 32816, USA.
authors.forename: Jaekyun
authors.initials: J
authors.lastname: Jeon
authors.forename: Michael S
authors.initials: MS
authors.lastname: Lodge
authors.forename: Ben D
authors.initials: BD
authors.lastname: Dawson
authors.forename: Masa
authors.initials: M
authors.lastname: Ishigami
authors.forename: Frank
authors.initials: F
authors.lastname: Shewmaker
authors.forename: Bo
authors.initials: B
authors.lastname: Chen
mesh_terms: D006108:Graphite; D046529:Microscopy, Electron, Transmission / Q000379:methods*
chemical_list: D006108:Graphite