Cryo-EM reaches yet another milestone – Comments on two recent cryo-EM atomic resolution studies
Two studies published during last two weeks have reported that single particle cryo-EM data can be now resolved to 1.20Å or 1.25Å, respectively. The groups of Sjors H.W. Scheres (LMB-MRC, Cambridge) and Holger Stark (MPI Göttingen) have for the first time shown that atomic resolution is attainable by single particle cryo-EM. The cryo-EM maps of apoferritin utilized as a model system in both studies reveal densities of single atoms including the hydrogens. The single particle cryo-EM thus becomes a method capable of reaching atomic resolution. Both studies stress that the use of the electron source with minimal energy dispersion of the emitted electrons is a key for obtaining cryo-EM maps with <1.5Å resolution. This is achieved by utilization of the cold field emission gun (CFEG) or standard Schottky field emission gun and monochromator. Different strategies have been implemented to suppress the optical aberrations which play crucial role at resolutions <1.5Å. The group of H. Stark utilized the newly developed image corrector referenced as BCOR in their Titan Krios microscope to minimize the aberrations directly during data acquisition, whereas the group of S.H.W. Scheres used standard Titan Krios microscope without image corrector and deconvolved the optical aberrations at the level of the data processing within their Relion software. In addition, the study performed at LMB-MRC Cambridge utilizes image filter for filtering out of the inelastically scattered electrons and last generation of the direct electron detector Falcon4. Although the number of particles required to reach the 1.2Å cryo-EM maps differ between the two studies, both papers agree that 1.6-2.0Å resolution maps shall be attainable on the currently standard 300kV cryo-TEMs, which are not equipped with the presented technical advancements.
Upgrade of the workflow for cryo-electron tomography and microscopy
The CIISB Cryo-electron microscopy core facility at CEITEC Masaryk University is expanding its services in the sample preparation for electron microscopy. The facility has recently acquired high-pressure freezer Leica EM ICE for vitrification of bulky biological specimen (up to 200 mm thickness). In addition, the freeze-substitution unit Leica EM AFS2 for resin embedding of the high-pressure frozen samples and the ultramicrotom Leica EM UC7 with the adapter for cryo-ultramicrotomy were purchased in order to provide the facility users with the complete workflow for preparation of thin section samples for both room-temperature electron microscopy and cryo-electron microscopy.
Emerging Topics in Biomolecular Magnetic Resonance – Nick Cox & Kendra Frederick
The series Emerging topics in Biomolecular Magnetic Resonance will continue on July 9th at 16:00 CEST with the following lecturers and topics:
Nick Cox (Australian National University): Spin state evolution during the biological water splitting reaction
Kendra Frederick (UT Southwestern): In cell structural biology enabled by DNP MAS NMR
Emerging Topics in Biomolecular Magnetic Resonance – 4th edition
The series Emerging topics in Biomolecular Magnetic Resonance will continue on June 25th at 16:00 CEST with the following lecturers and topics:
Melinda J. Duer (University of Cambridge): Understanding extracellular matrix disease states with solid-state NMR?
Claudio Luchinat (University of Florence): NMR for metabolomics: again the ‘second best’ technique?
Emerging Topics in Biomolecular Magnetic Resonance – 3rd edition
The series Emerging topics in Biomolecular Magnetic Resonance will continue on June 18th at 16:00 CEST with the following lecturers and topics:
Tuo Wang (Louisiana State University): Elucidation of carbohydrate structure in plant biomass and fungal pathogens using solid-state NMR and DNP methods
Rina Rosenzweig (Weizmann Institute of Science): Molecular Chaperones in Protein Disaggregation - What we can learn from NMR