GM/CA@APS: A Macromolecular Crystallography Resource - The primary goal of the GM/CA@APS Resource is to provide user access to cutting-edge
macromolecular crystallography beamlines to determine 3-D atomic structures of forefront problems in
structural biology. The Resource was founded in 1999 and has been in operation as a national user
facility since 2004, providing a full array of cutting-edge technologies for macromolecular crystallography
in Sector 23 at the Advanced Photon Source (APS), Argonne National Laboratory. GM/CA is led by
Robert Fischetti (Argonne National Laboratory, contact PI) and Janet Smith (University of Michigan, PI)
with an effective administrative structure to operate, maintain, and upgrade the beamlines, and run a
high-impact user program. The GM/CA macromolecular crystallography core provides a modern,
powerful environment with sophisticated tools for sample screening, interrogation and data collection in
fixed-energy, SAD and MAD modes through operation of two insertion-device X-ray beamlines, 23ID-B
and 23ID-D, from canted-undulator sources. The beamlines are independently tunable over a wide
energy range and are built to deliver a brilliant X-ray beam with exceptionally stable position and intensity.
The exceptional stability makes GM/CA an ideal facility for anomalous scattering, and users can quickly
(few minutes) change energy at will within the 5.0-20 keV range (λ = 2.48 Å - 0.62 Å). The stable beam
enables a powerful microcrystallography capability. Small beams for microcrystallography are created by
a quad mini-beam collimator with user-selectable beam sizes of 5-, 10- and 20-micron diameter in
addition to the full beam. Users can rapidly (within seconds) change beam size for any sample at any
time without beam realignment. The beamlines are equipped with fast, low-noise pixel-array detectors,
an Eiger 16M on 23ID-B and a Pilatus3 6M on 23ID-D. Cryo-protected samples are robotically mounted
from a 288-sample Dewar and can be visualized and manipulated in the beam with micron precision.
Users control the beamlines and samples with the intuitive and biologist-friendly JBluIce graphical user
interface. JBluIce includes GUI-based functions for beamline control, sample centering, sample
screening, data collection, X-ray fluorescence energy scan, raster scan of the sample, and data analysis.
The powerful raster feature is used to scan fields of micro-crystals or to find the best diffracting region of
a larger crystal. Information from raster scans can be shared with the data collection routine for a variety
of data collection options. The data analysis routines provide unit cell and resolution estimates to
formulate a strategy for data collection, which is automatically coupled to three data processing pipelines,
providing users with feedback in near realtime. During the 2016-2018 period, a total of 857 unique
individuals from 157 unique groups used GM/CA beamlines, and annually interrogated 35,000 samples,
deposited 225 structures in the PDB, and published 130 papers (12% in Nature, Science, and Cell).
Serial crystallography methodologies are implemented and integrated into the JBluIce automated data
collection and processing pipelines for both viscous injector and fixed-target sample delivery
technologies. A computing cluster and storage array network provides high-speed data storage, retrieval,
backup, and realtime data processing. Users receive training from an expert staff, and can collect data
on-site or remotely. The staff also contribute to a variety of community outreach activities including the
annual CCP4/APS Crystallography School. A biochemistry lab provides essential capabilities for sample
preparation and characterization adjacent to the beamlines. A proactive maintenance plan ensures the
high level of performance and minimizes downtown. A major upgrade of beamline optics, endstation, and
computing resources will prepare GM/CA for the planned 2023 arrival of a new storage ring source known
as APS-U. The new optics will enable a focused, 1-micron beam, and the new source will increase
brightness by 100-fold compared to the current APS. Outreach activities, user workshops, and new user
training materials will prepare the user community for the opportunities and challenges of APS-U.