https://3demmethods.i2pc.es/index.php?action=history&feed=atom&title=2022Kreutzberger_Review 2026-05-01T09:56:17Z Revision history for this page on the wiki MediaWiki 1.44.2 https://3demmethods.i2pc.es/index.php?title=2022Kreutzberger_Review&diff=4925&oldid=prev 2025-01-30T11:59:12Z

<p>Created page with &quot;== Citation == M. A. Kreutzberger, R. R. Sonani, and E. H. Egelman, “Cryo-EM reconstruction of helical polymers: Beyond the simple cases,” Quarterly reviews of biophysics, vol. 57, p. e16, 2024. == Abstract == Helices are one of the most frequently encountered symmetries in biological assemblies. Helical symmetry has been exploited in electron microscopic studies as a limited number of filament images, in principle, can provide all the information needed to do a t...&quot;</p> <p><b>New page</b></p><div>== Citation ==<br /> <br /> M. A. Kreutzberger, R. R. Sonani, and E. H. Egelman, “Cryo-EM reconstruction of helical polymers: Beyond the simple cases,” Quarterly reviews of biophysics, vol. 57, p. e16, 2024.<br /> <br /> == Abstract ==<br /> <br /> Helices are one of the most frequently encountered symmetries in biological assemblies. Helical<br /> symmetry has been exploited in electron microscopic studies as a limited number of filament<br /> images, in principle, can provide all the information needed to do a three-dimensional reconstruction<br /> of a polymer. Over the past 25 years, three-dimensional reconstructions of helical<br /> polymers from cryo-EM images have shifted completely from Fourier–Bessel methods to singleparticle<br /> approaches. The single-particle approaches have allowed people to surmount the<br /> problem that very few biological polymers are crystalline in order, and despite the flexibility<br /> and heterogeneity present in most of these polymers, reaching a resolution where accurate<br /> atomic models can be built has now become the standard. While determining the correct helical<br /> symmetry may be very simple for something like F-actin, for many other polymers, particularly<br /> those formed from small peptides, it can be much more challenging. This review discusses why<br /> symmetry determination can be problematic, and why trial-and-error methods are still the best<br /> approach. Studies of many macromolecular assemblies, such as icosahedral capsids, have usually<br /> found that not imposing symmetry leads to a great reduction in resolution while at the same time<br /> revealing possibly interesting asymmetric features. We show that for certain helical assemblies<br /> asymmetric reconstructions can sometimes lead to greatly improved resolution. Further, in the<br /> case of supercoiled flagellar filaments from bacteria and archaea, we show that the imposition of<br /> helical symmetry can not only be wrong, but is not necessary, and obscures the mechanisms<br /> whereby these filaments supercoil.<br /> <br /> == Keywords ==<br /> <br /> == Links ==<br /> <br /> https://www.cambridge.org/core/journals/quarterly-reviews-of-biophysics/article/cryoem-reconstruction-of-helical-polymers-beyond-the-simple-cases/F9ED5390A396E502657F02D7D27773C6<br /> <br /> == Related software ==<br /> <br /> == Related methods ==<br /> <br /> == Comments ==</div>

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