Critical importance of the correction of contrast transfer function for transmission electron microscopy-mediated structural biology

Background: Transmission electron microscopy (TEM) is an excellent tool for studyingdetailed biological structures. High-resolution structure determination isnow routinely performed using advanced sample preparation techniques andimage processing software. In particular, correction for contrast transferfunction (CTF) is crucial for extracting high-resolution information fromTEM image that is convoluted by imperfect imaging condition. Accuratedetermination of defocus, one of the major elements constituting the CTF, ismandatory for CTF correction. Findings: To investigate the effect of correct estimation of image defocus andsubsequent CTF correction, we tested arbitrary CTF imposition onto theimages of two-dimensional crystals of Rous sarcoma virus capsid protein. Themorphology of the crystal in calculated projection maps from incorrect CTFimposition was utterly distorted in comparison to an appropriatelyCTF-corrected image. Conclusion: This result demonstrates critical importance of CTF correction for producingtrue representation of the specimen at high resolution.