Protein complexes in focus

Abstract

A new advance in electron microscopy can reveal highly-detailed structures of protein complexes.

Keywords: biophysics; cryo-EM; none; phase plate; single particle analysis; structural biology.

Figure 1.. Simulations showing how a quarter-wave phase plate improves the contrast of in-focus images.

In these simulations the intensity of the beam (which can be made of light or electrons) remains the same everywhere it passes though the “transparent" object; however, the phase changes significantly where the beam passes through different parts of the object. (A) A perfectly focused, bright-field image has almost no contrast because it can only show variations in the transmitted intensity. (B) A defocused image is able to capture at least a small part of the changes in the phase, so the contrast is better and the object can be seen. (C) Zernike realized that changing the phase of the unscattered portion of the transmitted wave (that is, the part that was not deflected when the wave passed through the object) by 90 degrees greatly improved the quality of the image. The scientist in the photograph is Professor Kuniaki Nagayama, who has played a seminal role in the development of phase plates for use in the transmission electron microscope. Image credit: Dr. Radostin Danev.