Page 184 - Macromolecular Crystallography

CHAPTER 12

High-throughput crystallographic

data collection at synchrotrons

Stephen R. Wasserman, David W. Smith, Kevin L. D’Amico,
John W. Koss, Laura L. Morisco, and Stephen K. Burley

12.1 Introduction between 30 and 100 microns in their longest dimen-
The discussion in Chapter 5 on in-house data collec- sion are routinely used to determine the desired
tion methods highlighted the effect that advances in protein structure. Given the often prodigious effort
current technology have had on laboratory protein required to grow larger crystals, synchrotron beam-
crystallography. There have been parallel develop- lineshaveprovencosteffectivewhencomparedwith
ments in macromolecular crystallography utilizing in-house sources, despite their initial construction
modern synchrotron X-ray sources. The success cost of US$5 to $10 million per beamline.
of these efforts, combined with the recent scien- Unlike home X-ray sources, which are limited to
tific emphasis on genomics and proteomics, has a few specific wavelengths corresponding to the K α
yieldedathrivingstructuralbiologycommunitythat radiation from elements such as copper, molybde-
routinely uses these tunable, high-intensity X-ray num, and chromium, synchrotrons provide access
sources for crystallographic experiments. to a continuous range of X-ray energies. During the
The development of X-ray synchrotrons over the 1980s, it was recognized that matching the energy
last four decades and their use for X-ray analyses of the X-ray photon to the absorption edge of an
have been detailed elsewhere (Mills, 2002). Syn- atom within the protein crystal offers the possibil-
chrotron sources offer several advantages for the ity of extracting, from a single protein crystal, all the
acquisition of diffraction data from protein crystals. phase information required for the structure deter-
They provide extremely intense beams, with photon mination (Hendrickson, 1991). Successful replace-
fluxes that are many orders of magnitude greater ment of methionine residues within a protein with
than those available from rotating anode sources. selenomethionine results in a crystal that is struc-
Current, third-generation synchrotrons make use turally isomorphous to the crystal from the native
of insertion devices, that is devices inserted into protein and contains an element, selenium, ideal for
the main synchrotron ring, to produce very small, direct determination of experimental X-ray phases.
highlydirectionalX-raybeams. Winickhasprovided A discussion of anomalous dispersion methods can
a qualitative description of the insertion devices, be found in Chapters 8 and 9.
called undulators and wigglers, which are used to These technical developments stimulated a dra-
generate these X-ray beams (Winick, 1987). Particu- matic growth in the number of beamlines available
larly when undulators are used, the X-ray beam is for protein crystallography. There are currently at
highly collimated, delivering all of the photons into least 22 synchrotrons worldwide supporting stud-
a small area. ies of the crystalline forms of proteins, with a
Having such bright, intense X-ray beams enables further three under construction. In 2006, the num-
examination of very small protein crystals. Samples ber of beamlines used for protein crystallography

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