Coherent electron dynamics in a periodic array of C60 molecular targets driven by intense x-ray pulses of femtosecond duration.

Extracting structure-factor moduli from diffraction patterns of protein nanocrystals is one of the critical issues of serial femtosecond X-ray crystallography. Unlike a conventional crystallography experiment, serial femtosecond crystallography combines data from hundreds or thousands of crystals of varying size and quality, a situation reminiscent of powder diffraction. Here the whole-pattern fitting technique, originally designed for one-dimensional powder diffraction crystallography, has been reconsidered and applied to the analysis of higher-dimensional serial femtosecond X-ray crystallography data. For nanocrystals with a small number of unit cells, the whole-pattern fitting approach is shown to be more accurate than integration-based Monte Carlo methods.

The recent availability of extremely intense, femtosecond X-ray free-electron laser (XFEL) sources has spurred the development of serial femtosecond nanocrystallography (SFX). Here, SFX is used to analyze nanoscale crystals of -hematin, the synthetic form of hemozoin which is a waste by-product of the malaria parasite. This analysis reveals significant differences in -hematin data collected during SFX and synchrotron crystallography experiments. To interpret these differences two possibilities are considered: structural differences between the nanocrystal and larger crystalline forms of -hematin, and radiation damage. Simulation studies show that structural inhomogeneity appears at present to provide a better fit to the experimental data. If confirmed, these observations will have implications for designing compounds that inhibit hemozoin formation and suggest that, for some systems at least, additional information may be gained by comparing structures obtained from nanocrystals and macroscopic crystals of the same molecule.