Correction of artifacts in imaging tilted samples
(In collaboration with Tom Walz, Harvard University Lucas van Vliet, Department of Imaging Science & Technology, TU Delft).
When a tilted planar sample is projected onto the image plane, a significant optical artifact emerges, because a large fraction of this object will be outside the depth of focus of the optical system. This is a serious problem in collecting high-resolution phase information from a tilted 2D crystal for determining its atomic structure. Recent theoretical advances at the TU Delft and the University of Basel have provided novel algorithms to apply accurate corrections.
We want to implement such corrections schemes in a user friendly software package to advance electron crystallography. First, algorithms to determine the tilt geometry need to be developed and tested. Second, the principle of tilted sample CTF as developed by TU Delft will be applied to high-resolution images of AQP0 2D crystals recorded in the laboratory of Tom Walz, Harvard. The accuracy of phase values obtained after correction will be determined and error sources identified by comparison to phases calculated from the 1.9 Å structure of AQP0. To provide a robust and fast method to correct such imaging artifacts has important implications for high resolution EM in general