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BP: Fachverband Biologische Physik

BP 31: Imaging

BP 31.7: Vortrag

Freitag, 30. März 2012, 11:15–11:30, H 1058

In-focus phase contrast electron cryo-microscopy of biological samples with an electrostatic phase plate — •Daniel Rhinow¹, Andreas Walter¹, Manfred Lacher², Siegfried Steltenkamp², Sam Schmitz², Peter Holik², and Werner Kühlbrandt¹ — ¹Max-Planck-Institut für Biophysik, 60438 Frankfurt, Deutschland — ²caesar research center, 53175 Bonn, Deutschland

Although the instrumental resolution limit of the latest generation of transmission electron microscopes reaches 0.5 Å, a variety of physical factors limit the experimental resolution achievable with biological samples. Biological macromolecules are pure phase objects that are visualized by phase contrast, which in conventional cryoEM is generated by defocusing. Disadvantages of defocusing are weak contrast and incomplete transfer of object information, which impairs data collection and 3D reconstruction. A powerful alternative to defocus phase contrast is the use of a physical phase plate in the back focal plane of the electron microscope. The Boersch phase plate (BPP) comprises an electrostatic einzel lens shifting the phase of the unscattered electron beam by 90°, thus maximizing phase contrast for in-focus TEM. The PACEM (Phase Contrast Aberration-Corrected Electron Microscope) is a TEM prototype developed by Carl Zeiss NTS in collaboration with the MPI of Biophysics. BPPs have been tested in the PACEM. First BPP images of stained, unstained, and cryogenic biological specimens have been obtained.