Biological macromolecules can be imaged by single-particle cryogenic electron-microscopy (cryo-EM) without crystallization. This offers the possibility of imaging heterogeneous samples ? samples in which the macromolecule is in different conformational states. This research proposes a new method for analyzing such heterogeneous samples. Based on a Fourier-slice theorem for covariance functions, heterogeneity is analyzed by directly reconstructing 3d principal components and estimating the population densities of different conformations in the principal subspace, which is the subspace spanned by the principal components. This new methodology offers many advantages over the popular method of 3d classification: the new method works for continuous and discrete conformational states, it can organize conformational states in a meaningful way, and it can separate sample imperfections from conformational states. This research proposes to fully develop this methodology, validate it with simulations and real cryo-EM images, and release an open source software package for the use by the cryo-EM community.

Public Health Relevance

Electron microscopy provides detailed 3D pictures of large molecular complexes from cells, and has the potential to analyze how these molecular complexes work by changing their shape. This research seeks to develop novel software methods for such analysis.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
1R01GM125769-01
Application #
9419436
Study Section
Macromolecular Structure and Function C Study Section (MSFC)
Program Officer
Sammak, Paul J
Project Start
2018-03-01
Project End
2022-02-28
Budget Start
2018-03-01
Budget End
2019-02-28
Support Year
1
Fiscal Year
2018
Total Cost
Indirect Cost
Name
Yale University
Department
Radiation-Diagnostic/Oncology
Type
Schools of Medicine
DUNS #
043207562
City
New Haven
State
CT
Country
United States
Zip Code
06520