Cryo-EM image analysis

The group of Methods and Electron Microscopy aims at providing researchers efficient and user-friendly tools for three-dimensional structure determination and interpretation of electron microscopy images.

The recovery of high resolution 3D information from a set of noisy 2D images is a challenging mathematical/computational task.
If the sample has a helical symmetry, the use of this symmetry can allow great improvements in the quality of the 3D reconstruction. We have developed tools that help in the determination of this type of symmetry:

Helixplorer0
Helixplorer-0 is an auxiliary tool for Helixplorer-1. It allows to measure the distances and calculates the power spectrum (PS) of a 2D image (e.g. a cryo-EM class average) from which one intends to determine helical symmetry parameters using Helixplorer-1

Helixplorer1
Helixplorer-1 draws the theoretically expected pattern calculated from an ideal helix on the top of your experimental diffraction pattern. It then calculates a similarity score based on the average PS pixels in the areas where the pattern is ("the pattern" here means the peaks of a set of Bessel functions). The obtained scores are then plotted for all tested helical symmetry parameters as 1D or 2D graphs that you can click on.

Helixplorer2
Helixplorer-2 tries to make sense of the helical parameters in terms of a 2D crystal packing. A helix can be regarded as a particular kind of 2D crystal (or lattice) that can be rolled up to form a 3D helix. Helixplorer-2 highlights these aspects of a helix by explicitly imposing constrains on the characteristics of the lattice so that it can be folded to form a valid (seamless) 3D helix. Characteristics like crystal packing, bending energy, presence of a seam (as in the case of microtubules), etc. become more evident.

Further information, please contact : Leandro Estrozi.