6i5a
Tobacco Mosaic Virus
Structural highlights
Function[CAPSD_TMV] Capsid protein self-assembles to form rod-shaped virions about 18 nm in diameter with a central canal enclosing the viral genomic RNA. Publication Abstract from PubMedDirect electron detectors are an essential asset for the resolution revolution in electron cryo microscopy of biological objects. The direct detectors provide two modes of data acquisition; the counting mode in which single electrons are counted, and the integrating mode in which the signal that arises from the incident electrons is integrated. While counting mode leads to far higher detective quantum efficiency at all spatial frequencies, the integrating mode enables faster data acquisition at higher exposure rates. For optimal throughput at best possible resolution it is important to understand when the better performance in counting mode becomes essential for solving a structure and when the lower detective quantum efficiency in integrating mode can be compensated by increasing the number of particles in the data set. Here, we provide a case study of the Falcon III camera, which has counting mode capability at exposure rates of <0.9 e(-)/Px(2) and integrating mode capability at exposure rates above 10 e(-)/Px(2). We found that counting mode gives better resolution for medium sized complexes such as the beta-galactosidase (465kDa) (2.2A, 97% of Nyquist vs. 2.4A, 89% of Nyquist) with data sets of similar size. However, for larger particles such as Hepatitis B virus capsid like particles (4.8 MDa) we did not find any resolution gain in counting mode. Capabilities of the Falcon III detector for single-particle structure determination.,Song B, Lenhart J, Flegler VJ, Makbul C, Rasmussen T, Bottcher B Ultramicroscopy. 2019 Jan 28. pii: S0304-3991(18)30269-9. doi:, 10.1016/j.ultramic.2019.01.002. PMID:30738626[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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