EMIG Seminar: Valentin Peretroukhin, Ph.D. (Structura Biotechnology)

Speaker: Valentin Peretroukhin, Ph.D., Computational Research Scientist at Structura Biotechnology

Title: A matter of perspective: diagnosing and dealing with preferred orientation in cryo-EM

Preferred orientation, the tendency for a sample to assume one or more dominant orientations within cryo-EM data, can severely degrade map quality and prevent downstream model building and interpretation. In this talk, I will explain and motivate several quantitative ways to diagnose the presence of preferred orientation, with a particular emphasis on numerical tools within CryoSPARC. I will discuss several diagnostics, including the conical FSC area ratio (cFAR), a GSFSC analogue for identifying preferred orientation, and relative signal, a new diagnostic released with CryoSPARC v4.5, that directly relates 3D signal quality to viewing direction. Finally, using data from the publicly-available influenza hemagglutinin (HA) trimer dataset, I will walk through ways to mitigate the effects of preferred orientation without needing to prepare new samples or recollect additional data.  Namely, by identifying and mining for underrepresented views and carefully rebalancing data on the viewing sphere, I will show how one can glean similar map improvements from a baseline dataset with apparent preferred orientation, to those gained by recollecting data using a tilted stage.