Gabi Pragier (Tel-Aviv University)
One of the primary challenges in single particle reconstruction in cryo-electron microscopy is to find the three-dimensional structure of a molecule using its two-dimensional noisy projection-images. We suggest a method to estimate the unknown imaging orientations of all projection-images that is independent of their distribution. Since the relative orientation between each pair of images may only be estimated up to a two-way handedness ambiguity, we suggest an efficient procedure to remove these ambiguities by casting the problem as a graph-partitioning problem.
In addition, we present an algorithm for determining the three-dimensional structure of molecules that have a 4-way rotational symmetry. Our algorithm is based on self-common-lines whose location is related to the tilt angle of the underlying image's viewing-direction. These lines admit quite a few favorable geometrical constraints, thus enabling their detection even in extremely noisy settings.
We demonstrate the efficacy of our approach using simulated clean and noisy data.