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Beamtime available at CHESS, October 16 - December 13, 2013
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The CHESS/MacCHESS facility, located at Cornell University in Ithaca,
NY, invites macromolecular crystallographers and users of BioSAXS to
apply for time on one or more of our stations:
A1 station, monochromatic wiggler source, suitable for Se SAD
experiments as well as native data collection, with ADSC Q-210 detector.
F1 station, monochromatic wiggler source, suitable for Br SAD or native
data, with ADSC Q-270 detector and ALS-type automounter.
G1 station, wiggler source with multilayer optics, for BioSAXS experiments;
dual Pilatus 100-K detectors to record SAXS and WAXS data.
===== Special options ======
Pressure-cryocooling of (unfrozen) crystals is available by
prearrangement. This method can reduce the damage induced by
cryocooling, often with no need for cryoprotectants (Kim et al., Acta
Cryst. D61, 881-890 (2005)).
Microbeam (down to about 5 microns) using focusing capillary optics is
available on request at any of the stations.
======= Support =======
CHESS/MacCHESS provides a high level of support for all users. We are
very willing to help with non-standard experimental setups - just ask.
Our staff scientists also invite collaborations for more extended
projects investigating novel techniques.
Mail-in service is available - we will be pleased to collect (and
process, if you like) data from crystals that you send to us.
Remote data collection is available for crystallography experiments by
users familiar with the CHESS facility.
======== Applying for time ========
Visit http://www.chess.cornell.edu and look at "Online Express Mode" under the
"Users" menu. All applications can be done on line, any time. Processing
of proposals is rapid, with a turn-around time of just a couple of weeks.
More information is available on the web site, or contact administrator
Kathy Dedrick, [log in to unmask]
============ Recent developments ====================
Crystallography
---------------
Automounters of the ALS design (BAM-1 on F1, BAM-2 on A1) are available for
both local and remote crystal handling. New mounts facilitate rapid switchover
from standard 100-micron beam to capillary-focused 20-micron beam.
BioSAXS
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The primary station for BioSAXS has changed from F2 (dual-Si crystal mono)
to G1 (dual multilayer mono). A typical exposure time has been reduced from
10 seconds to 1 second. The accessible q range (combining SAXS and WAXS
data from 2 100-K Pilatus pixel array detectors) is about 0.006 - 0.8
inverse Angstroms. The standard X-ray energy is about 10 KeV.
Samples are handled using a sophisticated flow control system incorporating
a sample-loading robot, new disposable sample cells using a laser-cut
microchannel in place of a capillary, and a thorough cleaning cycle including
a blow-dry step. Control is through the Robocon interface, and preliminary
data reduction is carried out with the RAW software. Both systems are well
tested and maintained and RAW is open-source; all users are encouraged to
download it and install it on their own computers.
An Akta Purifier HPLC system equipped with a size-exclusion column (SEC) is
available for final sample preparation. UV and IR microspectrophotometers are
available for measuring sample concentrations, and new Wyatt instruments
provide DLS, MALS, and dRI capabilities. An in-line configuration of
SEC -> DLS/MALS -> in-beam flow cell is being assembled in the G1 hutch.
Much information about designing and carrying out a BioSAXS experiment is
available from the web site http://www.macchess.cornell.edu/biosaxs.html.
For more information on SAXS, contact Richard Gillilan,
[log in to unmask]
Pressure-cryocooling
--------------------
Pressure cryocooling has succeeded in improving the observed resolution of
diffraction data from users' crystals in a number of cases. In addition, it
has been able to increase the success rate for cryocooling crystals which had
previously yielded only one good "freeze" out of dozens or hundreds. In rare
cases, it has even caused twinned crystals to transform to untwinned.
Mounting options for pressure-cooling include (1) oil coated in a loop,
(2) in a liquid-filled capillary, and (3) the "capillary shielding" method
(Kim et al., J. Appl. Cryst. 46, 234-241 (2013)).
Reminder: pressure-cooling almost never improves crystals that are bad at
room temperature; what it does is reduce damage on cryocooling. Please
verify that your crystals show acceptable diffraction at room
temperature before requesting pressure-cooling.
Note that you will need to provide UNFROZEN crystals for pressure cryocooling;
new designs of crystallization plates (e.g. from MiTeGen) allow safe shipping
of such crystals, so you don't need to travel to CHESS.
For more information on pressure-cryocooling, contact Chae Un Kim,
[log in to unmask]
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