Superb resolution and contrast of transmission electron microscopy images of unstained biological samples on graphene-coated grids

• Published in: Biochimica et biophysica acta Vol. 1830; no. 6; pp. 3807 - 3815
• Main Authors: Jeon, Jaekyun, Lodge, Michael S., Dawson, Ben D., Ishigami, Masa, Shewmaker, Frank, Chen, Bo
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2013
• Subjects: Electron microscopy; graphene; Graphite; heavy metals; image analysis; Mass per length; Microscopy, Electron, Transmission - methods; Molecular structure; molecular weight; Prion; toxicity; transmission electron microscopy; Mass per length; Prion; Molecular structure; Electron microscopy
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2013.03.002

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. Single-layered graphene is used to support the protein self-assemblies of different molecular weights for qualitative and quantitative characterizations. 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. 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. 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. [Display omitted] •Unstained protein aggregation samples supported on graphene on a conventional TEM•Deposited in their native buffer conditions with image resolution and contrast comparable to negatively stained samples•Ideal for samples sensitive to buffer condition and avoid potential artifacts associated with staining•Reduced beam damage to samples and eliminates hazardous staining agents