Comparison of calculated and observed dynamical diffraction from purple membrane: implications

We show that the magnitude and direction of the observed differences in intensities of Friedel-related reflections in electron diffraction patterns from two-dimensional crystals of bacteriorhodopsin (purple membrane) are accounted for by dynamical scattering as well as by Ewald sphere curvature. We suggest how the observed Friedel differences might be used to refine structure factor phases.