Research

(In collaboration with Center for Biological Imaging, Institute of Biophysics, CAS)

Amorphous nickel titanium alloy film (ANTA film) and its performance. Electron micrographs of ANTA film are shown in low mag and high mag (Up left), respectively. Human apo-ferritin protein vitrified on ANTA film (up right) shows uniform particle distribution in comparison with conventional carbon film (bottom right). The improved conductance of ANTA film compared to conventional carbon film yields a smaller B factor computed from RH plot of single particle analysis data of the same human apo-ferritin sample (bottom left).
Cryo-electron microscopy (cryoEM) has become one of the most important approach for structural biology. However, barriers are still there for an increased successful rate, a better resolution and improved efficiency from sample preparation, data collection to image processing. CryoEM sample preparation is one of the bottlenecks with many efforts made recently, including the optimization of supporting substrate (e.g. ultra-thin carbon, graphene, pure gold, 2d crystal of streptavidin, and affinity modification), which was aimed to solve air-water interface problem, or reduce beam induced motion (BIM), or change particle distribution in the grid hole. Here, we report another effort of developing a new supporting substrate, the amorphous nickel-titanium alloy (ANTA) film, for cryoEM sample preparation as a layer of holey supporting film covering on TEM grid. Our investigations showed advantages of ANTA film in comparison with conventional carbon film, including much better electron conductivity and trace non-specific interaction with protein. These advantages yield less BIM and significantly improved particle distribution during cryoEM experiment of human apo-ferritn, thus resulting an improved reconstruction resolution from a reduced number of micrographs and particles. Unlike the pure gold film, the usage of the ANTA film is just same with the carbon film, compatible to conventional automatic cryoEM data collection procedure.
Reference:
Huang X.#, Zhang L.#, Wen Z., Chen H., Li S., Ji G., Yin C.C. and Sun F.* (2020) Amorphous nickel titanium alloy film: a new choice for cryo electron microscopy sample preparation. Progress in Biophysics and Molecular Biology. doi: 10.1016/j.pbiomolbio.2020.07.009 [Epub ahead of print]