MS23-P08 First preliminary results from TAAM-UBDB refinement on electron diffraction data Paulina Dominiak (Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Warszawa, Poland) Michał Chodkiewicz (Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Warszawa, Poland) Joanna Krzeszczakowska (Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, Warszawa, Poland)email: pdomin@chem.uw.edu.plCryo-electron microscopy and electron diffraction methods have made enormous progress in the last years and an increasing number of atomic and near atomic resolution structures are becoming available. At present, interpretation of collected data relay on a very approximate scattering model. The model is based on spherical independent atoms (IAM), ignoring the charge redistribution due to chemical bonding. This approximation may lead to unnecessary loss of information. We propose to base interpretation of data from cryo-electron microscopy and from electron diffraction methods on more realistic electron scattering models.
We are developing Transferable Aspherical Atom Models (TAAMs) from detailed electron densities of molecules and crystals. To build TAAMs we use a databank of aspherical atomic electron densities called UBDB [1]. Currently UBDB allow to reconstruct electron density of any protein, nucleic acid or other biologically important molecule. Thus, it gives also fast access to electrostatic potential.
It has been shown already [2] that replacement of the IAM by TAAM in x-ray crystallography leads to more accurate geometrical information and provide access to quantitative estimation of the electron density distribution and properties derived from it for molecules in a crystalline environment.
Given the fact that electron diffraction is more sensitive to charge density redistribution than x-ray we expect to see even more pronounced improvement after introduction of TAAM to analysis of electron diffraction/scattering.
We will present our first preliminary results of TAAM-UBDB refinements against electron diffraction data collected for paracetamol[3]. The figure illustrates the difference in crystal electrostatic potential (e/bohr) resulting from the differences between the IAM and the TAAM-UBDB electron scattering models.
References:

[1] Jarzembska, K. N. & Dominiak, P. M. (2012) Acta Cryst. A68, 139–147.

[2] Bąk, J. et al. (2011) Acta Cryst. A67, 141–153.

[3] Palatinus, L. et al. (2017) Science 355, 166–169.
Keywords: electron crystallography, UBDB, electrostatic potential modelling