A Bayesian View on Cryo-EM Structure Determination

Sjors H. W. Scheres

Journal of Molecular Biology · 2011 · 958 citations · 35 references

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TL;DR

Cryo‑EM single‑particle 3D reconstruction relies on many parameters estimated from extremely noisy data, making it prone to overfitting—especially near the resolution limit—and current ad hoc filtering introduces subjectivity. The study proposes a Bayesian interpretation of cryo‑EM structure determination, imposing smoothness on the reconstructed density through a Gaussian prior in the Fourier domain. This approach enforces smoothness by applying a Gaussian prior to Fourier coefficients, yielding an optimal linear filter without arbitrary tuning. Experimental results show that the Bayesian framework delivers more reliable structures, objective resolution estimates, and improved detection of smaller classes compared to existing methods.

Abstract

Three-dimensional (3D) structure determination by single-particle analysis of cryo-electron microscopy (cryo-EM) images requires many parameters to be determined from extremely noisy data. This makes the method prone to overfitting, that is, when structures describe noise rather than signal, in particular near their resolution limit where noise levels are highest. Cryo-EM structures are typically filtered using ad hoc procedures to prevent overfitting, but the tuning of arbitrary parameters may lead to subjectivity in the results. I describe a Bayesian interpretation of cryo-EM structure determination, where smoothness in the reconstructed density is imposed through a Gaussian prior in the Fourier domain. The statistical framework dictates how data and prior knowledge should be combined, so that the optimal 3D linear filter is obtained without the need for arbitrariness and objective resolution estimates may be obtained. Application to experimental data indicates that the statistical approach yields more reliable structures than existing methods and is capable of detecting smaller classes in data sets that contain multiple different structures.

References

35