Abstract
Serial diffraction data collected at the Linac Coherent Light Source from crystalline amyloid fibrils delivered in a liquid jet show that the fibrils are well oriented in the jet. At low fibril concentrations, diffraction patterns are recorded from single fibrils; these patterns are weak and contain only a few reflections. Methods are developed for determining the orientation of patterns in reciprocal space and merging them in three dimensions. This allows the individual structure amplitudes to be calculated, thus overcoming the limitations of orientation and cylindrical averaging in conventional fibre diffraction analysis. The advantages of this technique should allow structural studies of fibrous systems in biology that are inaccessible using existing techniques.
Highlights
The development of X-ray free-electron lasers (XFELs) has brought in a new era for the study of biomolecular structures (Chapman et al, 2011; Fromme, 2015)
In this paper we report on methods we have developed for processing the weak and sparse XFEL diffraction data obtained from single crystalline fibres of an amyloid-forming oligopeptide from the adenovirus shaft
A large number of diffraction patterns were collected, about 10% of which contain detectable diffraction from the fibrils, and about 10% of these are due to a single fibril in the beam focus and were used for analysis
Summary
The development of X-ray free-electron lasers (XFELs) has brought in a new era for the study of biomolecular structures (Chapman et al, 2011; Fromme, 2015). In this paper we report on methods we have developed for processing the weak and sparse XFEL diffraction data obtained from single crystalline fibres of an amyloid-forming oligopeptide from the adenovirus shaft. A large number of molecules are needed in the fibre specimen in order to obtain sufficient diffraction signal from conventional X-ray sources In these specimens the individual molecules (or small crystallites of molecules) adopt different random rotations about the axis of orientation, i.e. the specimen is cylindrically disordered. XFELs offer the potential to overcome the primary limitations of traditional fibre diffraction analysis by measuring the diffraction from single molecules, opening up diffraction studies of a much wider range of fibrous assemblies than has previously been possible This results from the possibility of injecting fibrous particles into the X-ray beam using a liquid jet, inducing flow alignment of the individual high-aspect-ratio particles.
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