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Direct phasing in femtosecond nanocrystallography. I. Diffraction characteristics
Author(s) -
Chen Joe P. J.,
Spence John C. H.,
Millane Rick P.
Publication year - 2014
Publication title -
acta crystallographica section a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.742
H-Index - 83
ISSN - 2053-2733
DOI - 10.1107/s2053273313032038
Subject(s) - diffraction , femtosecond , optics , phase retrieval , phaser , fourier transform , electron diffraction , laser , phase (matter) , noise (video) , x ray crystallography , materials science , bragg's law , amplitude , physics , computer science , image (mathematics) , quantum mechanics , artificial intelligence
X‐ray free‐electron lasers solve a number of difficulties in protein crystallography by providing intense but ultra‐short pulses of X‐rays, allowing collection of useful diffraction data from nanocrystals. Whereas the diffraction from large crystals corresponds only to samples of the Fourier amplitude of the molecular transform at the Bragg peaks, diffraction from very small crystals allows measurement of the diffraction amplitudes between the Bragg samples. Although highly attenuated, these additional samples offer the possibility of iterative phase retrieval without the use of ancillary experimental data [Spence et al. (2011). Opt. Express , 19 , 2866–2873]. This first of a series of two papers examines in detail the characteristics of diffraction patterns from collections of nanocrystals, estimation of the molecular transform and the noise characteristics of the measurements. The second paper [Chen et al. (2014). Acta Cryst. A 70 , 154–161] examines iterative phase‐retrieval methods for reconstructing molecular structures in the presence of the variable noise levels in such data.