Laser Phase Plate for SingleParticle Analysis and Tomography

Cryo-EM is a powerful technique that can visualize biomolecules in their near-native state, but suffers from the low contrast of biospecimens and their sensitivity to electron radiation. A phase plate addresses this challenge by shifting the phase of the unscattered beam by exactly 90 degrees relative to the scattered electrons, thereby enhancing image contrast. In this talk I will present the development of the laser phase plate (LPP), which uses a high-intensity cavity to amplify laser light to interact with electrons. Compared to previous approaches, this circumvents the need for placing material objects in the electron beam-path and has been demonstrated to provide a stable phase shift. We have recently built and implemented a LPP in a state-of-the-art Krios microscope equipped with a custom transfer optics module. This integration has led to several improvements, including better aberration correction of the electron beam, improved LPP hardware design and higher throughput for data collection. This opens up exciting new possibilities for single-particle analysis and tomography of biological samples with the LPP, which we are now beginning to explore in full capacity.