Page 195 - Macromolecular Crystallography

184 MACROMOLECULAR CRYS TALLOGRAPHY

cloning, gene expression/solubility testing, protein be made by a crystallographer, we have greatly
purification, crystallization, cocrystallization with enhanced throughput in data collection operations
small molecule ligands, cryopreservation, crystal at SGX-CAT.
evaluation, diffraction data collection, data reduc-
tion, and structure determination and validation. 12.10 Beamline monitoring and
Since samples are shipped to SGX-CAT from SGX maintenance
headquarters in San Diego, locations of the samples
on canes and within the shipping dewars are also Synchrotron beamlines are a complex hybrid of
stored within the database. Other information, such hardware and software. Although current designs
as the assignment of barcodes to a particular project, have achieved a level of robustness inconceivable
is also readily retrievable. As of January 2007, the a decade ago, tight process control is essential. For
volume of data maintained within our database was example, at SGX-CAT the position of the beam is
◦
approximately 60 GB, of which approximately two- controlled to within 0.5 µradians (0.000028 ). This
thirds were graphics images, such as spectra or tolerance corresponds to keeping the X-ray beam
electron density maps. The SGX database currently centroid within a 25 µm diameter circle at a loca-
consists of over 300 tables, approximately 2000 indi- tion 50 m from the undulator source. This perfor-
vidual columns (fields), and more than 200 triggers mance, reflecting the combined capabilities of the
and procedures to update related sections of the synchrotron and the beamline, is impressive to say
database when required. the least.
SGX-CAT maintains a direct T1 network connec- At SGX-CAT, beam alignment is accomplished
tion from the Advanced Photon Source in Illinois automatically. A two-stage process first maximizes
to SGX San Diego. Database inquiries are handled theintensityofthebeamexitingthemonochromator.
over this link. Interactions with the database occur in Combined motions of the robot and the monochro-
three ways. An extensive web-based system is used mator are then used to place the X-ray beam directly
for data entry and retrieval. For crystals generated at the sample position. In addition, critical compo-
by external users of the beamline, upload of an elec- nents, including the operational parameters of the
tronic spreadsheet transfers the required crystal data cryostream, the sample robot, and the X-ray inten-
attributes to the SGX LIMS. For automated opera- sity monitor are continually assessed. If any drift
tions, such as crystal screening and data collection, out of their allowed tolerance is detected, a beam-
custom scripts place the computed results directly line staff member is automatically notified through
into the database. a paging system. Necessary adjustments can then be
Since the SGX LIMS contains virtually all informa- performed, in many cases via remote internet access
tion on the provenance and results from a particular to the beamline control system.
sample, the data therein are available to track the Continual vigilance and routine maintenance is
progress of individual crystals at the beamline. The required to ensure this level of performance. While
interface supporting this functionality is shown in ongoing maintenance is not difficult, it is a critical to
Fig. 12.5. This web page is automatically updated ensuring optimal beamline performance. Thus, data
every15 min, providingnearreal-timeassessmentof collection and beamline control by a dedicated, pro-
sample progression at SGX-CAT. The display moni- fessional staff appears decidedly preferable to that
tors the status of up to 380 crystals, providing access by occasional users.
to more than 40 fields of data and the diffraction
screening images for each crystal. This LIMS tool
12.11 High-throughput data collection:
uses the results of automated crystal evaluation to
an example
selectthebestcrystalwithinagroupofreplicatesam-
ples for data collection and monitors whether both We have in this chapter summarized various aspects
data collection and data processing activities have of data collection at a synchrotron beamline. In this
completed successfully. As this interface handles section, the operations of SGX-CAT are presented to
most of the routine decisions that would normally illustrate these concepts in action.