The National Institutes of Health (NIH), through its Biotechnology Resource Program, supports a facility, called MacCHESS, to support macromolecular diffraction at CHESS. The Facility makes available additional support equipment and expertise for these studies. Briefly described below, specialty equipment such as crystal cooling devices, a binocular microscope, the image plate storage phosphors, CCD detectors, and various oscillation Laue cameras and fast shutters are provided. The CHESS darkroom is especially equipped for film techniques compatible with macromolecular diffraction. Access to this support facility is arrived at through the Standard CHESS Proposal form. Brief access for 24-48 hours to collect a data set on a crystal can be made on an Express Mode Proposal Form. See the section on "Allocation of x-ray beamtime" for more information.
Cryo-crystallography
Collection of macromolecular crystallography data at low temperatures,
first developed at CHESS, enables the collection of complete data sets
before crystals decay in the high flux synchrotron X-ray beams.
Nitrogen stream equipment with auto-fill capability is available for
routine data collection at 100 K at all MacCHESS stations. An FTS
cooler is still available at the F1 station for experiments conducted at
non-cryostatic temperatures. Contact MacCHESS in advance if you
plan to use non-routine setups.
Crystal Centering GUI xtal in Mitegen mount.
Image plates & scanners
Storage phosphor image plates are no longer routinely used for
macromolecular crystallography data at CHESS, but are still available
for unusual experiments at station F1. They have good spatial resolution, digitizing an 8" x 10" area into
approximately 2000 x 2500 100x100 micron2 pixels. They also have a very high dynamic range
of 104, and do not suffer from count rate limitations as do multiwire proportional
counters. Also, the 10 megabyte image is immediately available for evaluation on the
computer screen. We have two Fuji BAS 2000 scanners in available. These fast, compact
units digitize an image in less than 2 minutes. For more information on the scanner
system, contact Bill Miller.
CCD data collection
Higher intensity beamlines at synchrotron sources have driven the
development of new x-ray sensitive detectors with enhanced performance
capabilities for the collection of macromolecular diffraction data.
Desired characteristics include improved sensitivity, dynamic range,
count rate, and efficiency of data collection. CHESS has actively
participated in the development of digital detectors and continues to do
so. All MacCHESS stations now routinely make use of CCD
(Charge-coupled device) detectors. Stations A1 and F2 utilize Area Detector Systems Corporation
(ADSC) Quantum 210 detectors with a 4k x 4k pixel mosaic of CCD chips.
Station F1 utilizes a pair of ADSC Quantum 4 detectors with a 2304 x
2304 pixel mosaic CCD. In 2005 the Quantum 4s at F1 will be
replaced with a single larger detector, currently under construction by
ADSC.
Crystal Handling Automation
A "click and center" graphical user interface with a high quality
digital video and motorized goniometers is now available for rapid
centering of crystals at stations A1, F1 and F2. An automated
crystal mounting mechanism modeled after the ALS design was recently
installed stalled in F1 and is available for use.
Computational Facilities
An assortment of Unix, Linux and MacOS computers are available at each
MacCHESS beamline and in the CHESS computer room for data processing.
RAID storage and gigabit networking help to facilitate fast collection
and reduction of data. Several of the most popular data reduction
packages are available, including Denzo & Scalepack, HKL2000, MosFLM,
DPS and Scala. A few general crystallographic software packages
are available, including CCP4, O and SOLVE. A variety of methods
for data backup and transfer are supported, including tape, portable
disks, network transfer and optical media. MacCHESS maintains two
Linux Beowulf clusters which can be made available for large
computational tasks. Consult the
MacCHESS web site for
more details.
