Reducing cryoEM file storage using lossy image formats

Recent advances in instrumentation and software for cryoEM have increased the applicability and utility of this method. High levels of automation and faster data acquisition rates require hard decisions to be made regarding data retention. Here we investigate the efficacy of data compression applied to aligned summed movie files. Surprisingly, these images can be compressed using a standard lossy method that reduces file storage by 90-95% and yet can still be processed to provide sub-2 Å reconstructed maps. We do not advocate this as an archival method, but it may provide a useful means for retaining images as an historical record, especially at large facilities.

Routine single particle CryoEM sample and grid characterization by tomography

Single particle cryo-electron microscopy (cryoEM) is often performed under the assumption that particles are not adsorbed to the air-water interfaces and in thin, vitreous ice. In this study, we performed fiducial-less tomography on over 50 different cryoEM grid/sample preparations to determine the particle distribution within the ice and the overall geometry of the ice in grid holes. Surprisingly, by studying particles in holes in 3D from over 1000 tomograms, we have determined that the vast majority of particles (approximately 90%) are adsorbed to an air-water interface. The implications of this observation are wide-ranging, with potential ramifications regarding protein denaturation, conformational change, and preferred orientation. We also show that fiducial-less cryo-electron tomography on single particle grids may be used to determine ice thickness, optimal single particle collection areas and strategies, particle heterogeneity, and de novo models for template picking and single particle alignment.

Big data in cryoEM: automated collection, processing and accessibility of EM data

The scope and complexity of cryogenic electron microscopy (cryoEM) data has greatly increased, and will continue to do so, due to recent and ongoing technical breakthroughs that have led to much improved resolutions for macromolecular structures solved using this method. This big data explosion includes single particle data as well as tomographic tilt series, both generally acquired as direct detector movies of ∼10-100 frames per image or per tilt-series. We provide a brief survey of the developments leading to the current status, and describe existing cryoEM pipelines, with an emphasis on the scope of data acquisition, methods for automation, and use of cloud storage and computing.