The National Institutes of Health (NIH), through its National Institute of General Medical Sciences (NIGMS), funds MacCHESS for two purposes: core research and support of CHESS users, who perform macromolecular diffraction experiments. MacCHESS staff conduct research in the areas of cell signaling, micro diffraction, membrane proteins, optimized data collection at synchrotron sources, crystallographic phasing, large unit cell crystallography, x-ray optics for crystallography and other areas relevant to macromolecular crystallography. On the user support front, the facility makes available specialized equipment and expertise, in addition to those provided by CHESS to all users. MacCHESS staff provide training and advice in the use of all these amenities. Guidance in determining MacCHESS's major emphases is provided by the MacCHESS Advisory Committee.
BioSAXS Essentials: Getting Started in Biological Small-Angle X-ray Solution Scattering
BioSAXS
Small-Angle X-Ray Solution Scattering (SAXS) at MacCHESS. Protein envelope reconstruction. Increasingly, BioSAXS is becoming an indispensable tool in molecular and structural biology. Because the technique is applicable to a very wide range of solution conditions (concentration, pH, ionic strength, temperature, additives, etc.) and because it gives information on systems without crystals, even disordered systems, it has become an important tool for gleaning structural information early in the research process, for diagnosing problems, and for understanding structure and association under physiological conditions.
Microcrystallography
Microcrystallography refers to the ability to obtain useful structures from small (less than 30 microns) crystals, or small regions of "normal-sized" crystals that have bad growth habits or suffer from rapid radiation damage. This area of research is driven by scientists working on membrane proteins, for which crystal size is a major problem, or on proteins with needle-like growth habits.
Automation
Automounters are intended to help maximize throughput at synchrotron beam lines where heavy shielding and safety interlocks slow manual access to the experiment. A sizable number of crystals can be stored in the hutch, accessed randomly, mounted and dismounted; all without entering the hutch. A crystal automounter using the ALS design is available at the F1 and A1 stations.
Remote data collection
MacCHESS is now supporting remote access experiments for the
macromolecular crystallography user community. We use advanced software
tools that enable network based control of automated A1 and F1 beam
lines. Users with previous experience of data collection at MacCHESS are
able to screen samples and collect crystallographic data from remote
locations. MacCHESS has an ALS-style crystal automounter available at F1
beam line and the ALS second generation automounter is now operational
in A1. Users wishing to collect data remotely should indicate this on their
beamtime request form. For details on how to use the automounter please
go to Automation section and read more about
requirements for remote access.
A facility for cryocooling crystals under pressure is now
available at MacCHESS. This technique, developed in the Gruner lab, was
reported in (Kim et al., Acta Cryst. D61, 881 (2005)). It involves
mounting a crystal on a special pin, pressurizing it, cooling to liquid
nitrogen temperature, and then releasing the pressure while keeping the
crystal cold. The method can allow successful cryocooling using little
or no penetrating cryoprotectant, and can produce cryocooled crystals
of better quality than the usual cryocooling method. CHESS has actively participated in the development of CCD-based
detectors for crystallography, in collaboration with
Area Detector
Systems Corporation (ADSC); this activity is expected to
continue in the future. All MacCHESS stations are equipped
with ADSC CCD detectors: Stations A1 and F2 utilize Quantum 210
detectors, 4-chip devices with 4k x 4k 50-micron pixels and a
1-second readout time. Station F1 utilizes a
Quantum 270
detector, a similar but slightly larger device with an improved
sensitivity for weak data. Station F3 has a Quantum 4 detector,
which has 2304 x 2304 80-micron pixels and a somewhat slower readout
time but produces excellent data. A "click to center" Java-based graphical user interface
employing a high quality digital video camera is available for rapid
centering of crystals. Fully automatic centering is now also possible,
using the GUI's "Auto Center" button and the XREC software package. Acquisition of macromolecular crystallography data at low
temperatures, using some variation on the crystal mounting loops
first developed at Cornell, enables the collection of complete data
sets before crystals decay in the high flux synchrotron X-ray beams.
Oxford Cryosystems cooling devices with auto-fill capability are available
for routine data collection at 100 K at all MacCHESS stations. The temperature
is usually set to 100 K, but can be varied from 80 K to 400 K. A number of Linux computers are installed at each MacCHESS beamline
and in the CHESS computer room for data collection and processing.
Two terabytes of RAID storage are available at each station for user
data storage, and gigabit network connections throughout CHESS allow
rapid transfer of data during collection and processing operations. Popular data reduction packages are available, including HKL2000,
DPS/Mosflm/Scala, and XDS. Various general crystallographic
software packages are also available, including the full CCP4 Suite,
SOLVE/RESOLVE, Arp/wArp, BnP, CNS, Phenix, Coot, PyMol, and O.
A variety of methods for data backup and transfer are supported,
including portable disks, wired and wireless connections for laptop
computers, and network transfer to remote computers via sftp.
MacCHESS maintains a Linux Beowulf cluster which can be made
available for large computational tasks.
High Pressure cooling
Current station CCD configuration
Crystal Centering
Cryo-crystallography
Computational Facilities
Crystallography software
