Research

Structural Determination of Proteins and Molecular Assemblies

Unconstrained by crystal packing, the molecule in a single-particle specimen can be thought to exhibit the entire range of native conformations.  The ability to find the structure of each conformer is one of the most important potential assets of 3D cryo-EM of single particles.  On the other hand, the realization of high resolution for each of these conformers poses daunting problems of data collection and processing, considering the statistical requirements stated before.  Therefore, we are also interested in the development of efficient and robust computational methods of structure refinement and structure validation in the presence of multiple conformational or binding states.

We develop, in collaboration with other groups, a single particle software package SPARX/SPHIRE (Hohn, et al).  SPARX is provided free of charge as a service to the scientific community and its main features include:

1.     SPHIRE is driven by a user friendly GUI supported by a Wiki-based interactive documentation.
2.     New generation of 2D and 3D alignment protocols.
3.      Ab initio structure determination programs.
4.      Advanced code for multivariate statistical analysis (PCA, Varimax).
5.      Extensive C++ library of general and EM-specific image operations with Python bindings, thus accessible to Python programmer.
6.       All structure determination applications written as user transparent Python scripts.

SPARX is available for download at:  http://sparx-em.org

Research Interests:

Cryo-electron microscopy, single particle reconstruction.