Biophysical Society Thematic Meeting | Trieste 2024

Emerging Theoretical Approaches to Complement Single-Particle Cryo-EM

Poster Abstracts

33-POS Board 33 GHOSTBUSTER - A DIFFRACTION TOMOGRAPHY ALGORITHM FOR CRYO-EM PARTICLE REFINEMENT Joel Yeo 1,2 ; Benedikt J Daurer 3 ; Dari Kimanius 4 ; Deepan Balakrishnan 1 ; Tristan Bepler 5 ; Yong Zi Tan 1 ; N. Duane Loh 1 ; 1 National University of Singapore, Center for Bio-Imaging Sciences, Singapore, Singapore 2 Agency for Science, Technology and Research (A*STAR), Institute of Materials Research and Engineering (IMRE), Singapore, Singapore 5 New York Structural Biology Center, Simons Machine Learning Center, New York, NY, USA Continual advances in methods development for single particle imaging in cryogenic electron microscopy (cryoEM) have paved the way towards ever-increasing resolution for three dimensional (3D) particle reconstruction. For thicker particles, one has to further correct for the effects of multiple scattering within the particle. This is commonly associated with the correction of the Ewald sphere curvature, and existing algorithms have recently been successful in pushing the resolution limit beyond what was possible. However, the physics of cryo-EM image formation is better understood as in-line holography. This implies that the phases of the complex-valued field arriving at the detector are lost upon the measurement of particle images. Therefore, the Fourier coefficients inferred from these phase-less images, which are subsequently used in Ewald sphere curvature correction, cannot fully remove the effects of multiple scattering. This results in ghost-like artifacts in the reconstructed particle. Here, we develop an end-to-end diffraction tomography algorithm, named Ghostbuster, as an alternative approach to minimize the appearance of these ghost artifacts. Ghostbuster refines the 3D particle through batch stochastic gradient descent by minimizing the error between the estimated images from a multislice-based forward model and actual cryo-EM measurements. By accounting for the effects of multiple scattering, Ghostbuster demonstrates improved reconstructed particle resolution beyond traditional Ewald sphere curvature correction algorithms in existing state-of the-art software for both simulated and experimental datasets. 3 Diamond Light Source, Didcot, United Kingdom 4 CZ Imaging Institute, Redwood City, CA, USA

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