Dose and exposure requirements for the protein x-ray serial crystallography.

We have proposed spraying proteins (aligned by a laser) across a synchrotron beam to solve proteins which cannot be crystallized.$^{1}$ A single-file stream of ice-jacketed proteins is considered. We compute diffraction patterns for the GroEL at the incident x-ray flux predicted for a new coherent scattering beamline at the Advanced Photon Source. Using iterative phasing of the data, we determine the relationship between the count rate at a reconstructed pixel (or 3D voxel) of a given size in the real-space charge-density map and number N of proteins in the 10-$\mu $m 2 kV x-ray beam at any instant. A modulation transfer function estimates resolution for various exposure times. With the incident flux of 10$^{6}$ photons/s\textbf{/}nm$^{2}$ and N=10, over 5,000 counts/s are distributed over the entire diffraction pattern, which is sufficient for a nm resolution with 200 s exposure. We compare the results of this numerical lensless imaging experiment with a simple theoretical treatment of image formation in the dark and bright field phase contrast. Supported by ARO, NSF and co-workers.$^{1}$ $^{1}$J. Chem Phys. 123, 244304 .