Abstract
With the use of highly coherent femtosecond X-ray pulses from a free-electron laser, it is possible to record protein nanocrystal diffraction patterns with far more information than is present in conventional crystallographic diffraction data. It has been suggested that diffraction phases may be retrieved from such data via iterative algorithms, without the use of a priori information and without restrictions on resolution. Here, we investigate the extension of this approach to nanocrystals with edge terminations that produce partial unit cells, and hence cannot be described by a common repeating unit cell. In this situation, the phase problem described in previous work must be reformulated. We demonstrate an approximate solution to this phase problem for crystals with random edge terminations.
Highlights
The availability of brief, intense and coherent X-ray pulses produced by X-ray free-electron lasers (XFELs) has created the potential for major advancements in macromolecular crystallography [1,2]
Serial femtosecond crystallography (SFX) [3] is among the most successful new paradigms to emerge, which involves directing a stream of randomly oriented protein crystals across the focus of the XFEL beam
Whereas crystal size and shape distributions are of relatively little consequence, we show that the presence of molecular vacancies at the crystal boundaries obscure the notion of the crystal unit cell and necessitates a reformulation of the problem
Summary
The availability of brief, intense and coherent X-ray pulses produced by X-ray free-electron lasers (XFELs) has created the potential for major advancements in macromolecular crystallography [1,2]. SFX data often consist of hundreds of thousands of diffraction patterns, which can be collected in a matter of hours at current pulse-repetition rates These diffraction patterns are largely free from radiation damage [4] because the timescales of the relevant damage mechanisms are longer than the exposure time [5,6]. Whereas crystal size and shape distributions are of relatively little consequence, we show that the presence of molecular vacancies at the crystal boundaries obscure the notion of the crystal unit cell and necessitates a reformulation of the problem In this manuscript, we suggest an approximate means of solving this problem, which we demonstrate through simulations
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