Seminar Colour Guide:
External Faculty | External Postdoc | Company Representative Science and Society EMBL Distinguished Visitor Lecture Vision2020 Lecture Series Molecular Medicine Seminar | EIPOD Seminar | PSB Seminar | TAC Seminar Hamburg Speaker EMBL-La Sapienza Lecture
|External Faculty Speaker||
Abstract: Recent developments in the field of single-particle cryo-electron microscopy (cryo-EM) made it possible to obtain 3D reconstruction based atomic models. However in contrast to X-ray crystallography, the level of structural details is not as uniformly spread across the entire cryo-EM reconstruction, what causes the major difficulty in obtaining reliable atomic models for not well defined or flexible regions. This raises the need of developing new tools for multi-resolution fitting of atomic models and their validation or customization of the usage of existing programs.
Analysis of local Real Space Correlation Coefficient (RSCC) of over 200 near-atomic resolution structures deposited in the Electron Microscopy Data Bank (EMDB) revealed that only one third of those fit the deposited cryo-EM map at a level commonly accepted for large complexes determined at 3.8 2.8 Å resolution by X-ray crystallography. In addition, post-processing, like sharpening of the 3D reconstruction, could significantly affect the level of reliable structural features if performed in a sub-optimal way.
The quality and interpretability of cryo-EM maps used for building models of large macromolecular complexes is usually estimated based on the gold-standard Fourier Shell Correlation (FSC) criterion used to estimate the highest resolution limit of a 3D reconstruction. However using the same methodology to calculate FSC between cryo-EM map and the atomic model based map can be used to estimate to which resolution limit reliable structural features extend. The FCR methodology (Fourier Cross-Resolution) yields results that are in theory much less marred by the problems prevalent in FSC resolution estimation and could be used to estimate the highest resolution limit of a cryo-EM reconstruction.
|External Faculty Speaker|