Open AccessA 7 µm mini‐beam improves diffraction data from small or imperfect crystals of macromolecules
Author(s) -
Sanishvili Ruslan,
Nagarajan Venugopalan,
Yoder Derek,
Becker Michael,
Xu Shenglan,
Corcoran Stephen,
Akey David L.,
Smith Janet L.,
Fischetti Robert F.
Publication year - 2008
Publication title -
acta crystallographica section d
Language(s) - English
Resource type - Journals
ISSN - 1399-0047
DOI - 10.1107/s0907444908001741
Subject(s) - beam (structure) , synchrotron , beamline , laser beam quality , crystal (programming language) , materials science , diffraction , beam diameter , optics , physics , computer science , laser beams , laser , programming language
A simple apparatus for achieving beam sizes in the range 5–10 µm on a synchrotron beamline was implemented in combination with a small 125 × 25 µm focus. The resulting beam had sufficient flux for crystallographic data collection from samples smaller than 10 × 10 × 10 µm. Sample data were collected representing three different scenarios: (i) a complete 2.0 Å data set from a single strongly diffracting microcrystal, (ii) a complete and redundant 1.94 Å data set obtained by merging data from six microcrystals and (iii) a complete 2.24 Å data set from a needle‐shaped crystal with less than 12 × 10 µm cross‐section and average diffracting power. The resulting data were of high quality, leading to well refined structures with good electron‐density maps. The signal‐to‐noise ratios for data collected from small crystals with the mini‐beam were significantly higher than for equivalent data collected from the same crystal with a 125 × 25 µm beam. Relative to this large beam, use of the mini‐beam also resulted in lower refined crystal mosaicities. The mini‐beam proved to be advantageous for inhomogeneous large crystals, where better ordered regions could be selected by the smaller beam.