Laser Phase Contrast in cryo-EM for Visual Proteomics at Atomic Resolution

The laser phase plate (LPP) has recently demonstrated a nearly-ideal contrast transfer function (CTF) in transmission electron microscopy (TEM) at 300 keV, as well as freedom from the instability and irreproducibility of previous types of phase plates. It thus provides the ability to extract the maximum amount of information that is physically present in the electron beam. However, it requires a transfer optics system, which increases aberrations, and it has so far only been used in a modified Titan test microscope with a side-entry cold holder, hampering its usefulness for cutting-edge biological research.

This project will take the LPP to a much higher level by integrating it into the most modern Krios electron microscope. This combination will enable high-throughput data taking; fully compensate for the increases in aberration by using a gun monochromator as well as a Cs corrector; employ a more sophisticated design of the LPP to further improve the CTF; include an energy filter in order to optimize its use with thicker specimens; and benefit from the latest generation of electron-counting cameras. Together with collaborators, the project will explore the benefits of this ultimate phase contrast microscope in cryo-tomography.

The laser phase plate project is now a collaboration with the CZ Imaging Institute.