Previous Editions__________________________________________________________________________SSRL Headlines Vol. 10, No. 2 August, 2009__________________________________________________________________________
Contents of this Issue:
A research team led by Joseph Wedekind at the University of Rochester Medical
Center (NY) crystallized the smallest naturally occurring riboswitch known,
preQ1, from the hot spring bacterium Thermoanaerobacter
tengcongensis. They solved the structure using MAD phasing at SSRL Beam Line
7-1. The researchers observed that the RNA sequence forms a compact structure
with most of the RNA residues making multiple contacts to neighboring bases.
Such visualization accounted for the strong binding affinity of the riboswitch
to its metabolite and the conservation of specific bases in the RNA sequence.
Because riboswitches regulate the production of as many as 4% of bacterial
genes, understanding their form and function relationships may lead to a new
way to combat disease-causing bacteria that are resistant to current
antibiotics. The researchers will continue to investigate this riboswitch from
other bacterial species to determine if this method of metabolite binding and
gene regulation is conserved. This work was published in April 24 issue of the
Journal of Biological Chemistry.
Often, thin films of these polymer semiconductors are semicrystalline,
consisting of small regions or grains where the molecules are ordered; these
grains are separated by grain boundary regions where molecules are amorphous or
disordered. It is believed that charges can easily traverse the crystalline
grains, but are hindered by the disrupted structure at the grain boundaries. By
understanding exactly how the grain boundaries slow charge transport, the
polymer film microstructure can be engineered for improved performance.
Researchers at Stanford University, including graduate student Leslie Jimison
and Prof. Alberto Salleo, collaborated with SSRL staff scientist Mike Toney to
perform x-ray diffraction experiments at SSRL Beam Lines 11-3 and 7-2. The
researchers investigated the properties of unique, aligned thin films of
semicrystalline poly(3-hexylthiophene) (P3HT). Diffraction data gave insight
into film microstructure, including orientation of chains within grains and
possible grain boundary structure. In one direction of the anisotropic film,
there is the potential for polymer chains in adjacent crystallites to cross the
grain boundaries, which may make these grain boundaries less detrimental to
transport. Electrical measurements of thin film transistors confirmed that
charge transport is indeed more efficient in directions where this is more
likely to occur.
Results in this work help strengthen the understanding of the relationship
between polymer film microstructure and semiconductor performance by giving
insight into how crystalline orientation, which defines grain boundary
structure, can be optimized for efficient charge transport in electronic
devices. This work was published in the April 27 issue of the journal
Advanced Materials.
Other milestones we have met this year include the finishing of the SPEAR3 beam
line upgrade project, with the completion of three stations on Beam Line 4 and
successful routine user operation at 200 mA in top-off mode. This mode of
operation was the result of hard work from the accelerator, beam line and
Radiation Physics Department staff in close cooperation with the Department of
Energy Site Office. Ultimately, this mode of operation will allow us to deliver
stable beams at nearly constant current at up to 500 mA. Finally, DOE has come
through this year with almost 10 million dollars to enable SSRL to undertake
badly needed infrastructure and beam line upgrade projects.
As I mentioned at the beginning of this article, I wanted to discuss the
changing experimental portfolio at SSRL. Early in SSRL's history, the high
profile areas were in the development of x-ray absorption spectroscopy, surface
diffraction and core level photoelectron spectroscopy. These techniques are now
mature and are as strong as ever, being applied to real world applications
ranging from understanding photosynthesis to understanding how advanced
batteries work to the development of gate dielectrics for the integrated
circuits used in the PlayStation3. With the high brightness of SPEAR3, new
techniques are being developed and added to the capabilities being made
available to users. One of the new research areas is microscopy over a wide
range of length scales. Focused beams at the micron scale are being used at
Beam Line 2-3 to study how and where metals accumulate in plants and fish in
the environment. In addition, improvements in the focusing capabilities at Beam
Line 12-2 have allowed protein crystals as small as 5 microns to be studied. A
microscope employing zone plates to focus the beam is under development and
will soon provide 30 nm beams to study properties of magnetic domains at Beam
Line 13-1. Not only can x-rays be focused to probe materials in a small spot,
but they are being used in an actual x-ray microscope, at Beam Line 6-2, that
provides 2- and 3-dimensional images in real space at 30 nm resolution, showing
objects ranging from biomaterials such as bones and teeth to advanced fuel cell
materials and nanostructures. Rounding out SSRL's imaging capabilities is the
lensless imaging station at Beam Line 13-3, which uses the two-dimensional
pattern of soft x-rays scattered from the sample to image nanostructures at
resolutions better than 30 nm. The extreme capabilities of the Linac Coherent
Light Source will make it possible to use this technique to image objects at
Ångström resolution. Finally, the advent of the LCLS has also
resulted in a renewed interest in time-resolved studies at SPEAR3. This has
been made practical through the development of the low-alpha mode to give
shorter pulses and special fill patterns, for specific high intensity bunches
in SPEAR3 that can be synchronized with a pulsed laser at the beam line
experiment.
In this short article, I have been able to give only an incomplete summary of
research at SSRL, but I encourage you to scan through the
SSRL Science
Highlights for a more complete picture of the exciting results that are
coming out every week.
-Piero Pianetta
BL12-2 is the high-intensity, state-of-the-art undulator beam line for advanced
macromolecular crystallographic studies funded through The Gordon and Betty
Moore Foundation in cooperation with the California Institute of Technology.
The successful implementation of microbeam capability for studying
microcrystals and higher quality portions of larger crystals was recently
completed.
A precision goniometer, constructed in-house, based on a rotary air bearing
capable of exceeding speeds of 360 degrees/s and with a demonstrated a sphere
of confusion of ~1 mm was installed, and it includes
x, y and z stages for precise sample positioning. In addition, a new in-line
camera for viewing micron-sized samples along the beam axis was commissioned.
The in-line camera system, procured from Accel, was originally developed on the
ESRF microfocus Beam Line ID13. A new automated collimation system, designed
in-house, was also commissioned and collimates the focused beam to yield
smaller beams (20, 10 and 5 microns FWHM). Microcrystals of the virus-free
recombinant form of the polyhedra cypovirus (kindly supplied by Prof. P.
Metcalf [Metcalf et al., Nature 446, 97, 2007]) were used in the
initial commissioning studies. These crystals are typically 5 x 5 x 5
mm3 in
size and could be easily aligned with the precision goniometer and in-line
camera. A data set to 1.65 Å was recorded in less than 7 minutes,
marking a significant milestone for the advanced capabilities of BL12-2.
October 9 is the early registration deadline for the Annual SSRL/LCLS Users'
Conference and Workshops which will be held October 18-21, 2009. The event
kicks off on October 18 with a special symposium celebrating 35 years of
outstanding science at the Stanford Synchrotron Radiation Lightsource. In
addition to reviewing technical accomplishments and research highlights, future
scientific and technical opportunities for SSRL will be discussed.
LCLS/SSRL 2009 officially begins on October 19 with a joint plenary session
featuring updates from SLAC and DOE, a preview of the workshops, a user science
poster session, and a keynote presentation. The Spicer Young Investigator
Award, Klein Professional Development Award, Lytle Award, and the Outstanding
Student Poster Session Awards will be presented on this day.
On October 20, concurrent sessions will focus on SSRL and LCLS facility
development, instrumentation, and user science, followed by meetings of the
respective SSRL and LCLS Users' Organizations.
On October 21, several concurrent workshops will be held including
Microimaging; Nanoscale Imaging with the SSRL STXM; Macromolecular
Crystallography; Soft X-ray Beam Line Experiment Preparation; and X-ray Pump
Probe Experiment Preparation. Register for all events at:
The SSRL and LCLS Users' Organization Executive Committees need scientists to
represent their entire user community and interact with management to help
determine potential opportunities and strategic plans for the future.
With the exception of the chairs, elected members serve a three-year term.
Chairpersons, currently Wayne Lukens for the SSRL UOEC and Linda Young for the
LCLS UOEC, will serve on the committee for two additional years to facilitate
continuity of activities.
If this sounds like something that interests you, or perhaps a colleague,
submit your nomination(s) by September 29. See the following links for current
committee membership and the positions that need to be filled:
SSRL: http://www-conf.slac.stanford.edu/ssrl-lcls/2009/SSRL_UOECelection.asp
We invite you to share your research during the Poster Session of the Annual
Users' Meeting on October 19. We welcome posters on all photon science-related
research and development at SLAC and students, in particular, are encouraged to
present posters for the student poster competition. Representatives of the
Users' Organization will judge student posters and prizes (including $100.00
award) for the most outstanding posters will be presented during the meeting.
Additionally, students presenting posters are eligible to receive a free dinner
- just sign up and indicate this when you register.
Submit abstract:
Poster session instructions:
It is extremely important that users not only inform us whenever work conducted
at SSRL results in a publication, but also acknowledge SSRL and our funding
agencies in each publication. User help is needed to keep current records on
publications including refereed journal papers, conference proceedings, book
chapters and theses, invited lectures and major awards and patents based at
least in part on work conducted at SSRL. This information allows SSRL to
demonstrate scientific achievements and productivity when responding to
requests sent out by the Department of Energy and the National Institutes of
Health.
This information can be submitted anytime via email message to Lisa Dunn or
Cathy Knotts or via the reference submission form at:
For recent publications lists and the proper acknowledgement statements see:
The Third Annual Ultrafast X-ray Summer School (UXSS 2009) was held from June
15-19, 2009 at the SLAC National Accelerator Laboratory and sponsored by the
PULSE Institute for Ultrafast Energy Science. The summer school was a weeklong
residential event that brought together about 100 students, post-doctoral
researchers and other young and established scientists from diverse
backgrounds. Particular emphasis was given to new scientific opportunities
enabled by the world's first hard x-ray free electron laser, the Linac Coherent
Light Source (LCLS) which underwent a spectacular turn on only months before.
This year's school offered pedagogical lectures by world leading experts in
free electron laser and accelerator science, atomic molecular and optical
physics, condensed matter physics, physical chemistry and coherent imaging
covering both experiment and theory. In addition, a day of research talks
highlighted recent experimental advances. A special session was devoted to
possibilities for future light sources, and there was a historical perspective
of 35 years of photon science at SLAC. The summer students enjoyed a packed
schedule that included tours of the LCLS and SSRL as well as a trip to the
California Academy of Sciences; however, the highlight of the summer school may
well have been the competition for the best mock beam time proposal for LCLS in
which the students worked with LCLS and PULSE scientists to learn how to
propose a compelling and technologically sound proposal.
About PULSE: The PULSE Institute for Ultrafast Energy Science at SLAC and
Stanford University is jointly funded by the Department of Energy, Office of
Science Basic Energy Sciences division of Material Science and Engineering and
Chemical Sciences. More information on PULSE, the UXSS series and the LCLS can
be found respectively at:
If you are interested in requesting beam time on macromolecular beam lines
during the first scheduling period (Nov 2009 - Feb 2010) of our 2010
experimental run, submit your request(s) by September 15. For reference, the
2010 operating schedule including maintenance days, holiday shutdown periods,
etc., is available at:
Submit beam time requests by logging into the SSRL User Portal at:
Enter your email address and your password or click on 'request a password'.
Remember to submit a SEPARATE request for each beam time allotment requested.
We have tried to make the process to submit multiple requests easier by adding
a feature that allows you to clone a previous request.
If you would like beam time during this first scheduling period, but do not
have an active proposal, please submit a Rapid Access Request by September 15.
__________________________________________________________________________
SSRL Headlines is published electronically monthly to inform SSRL users,
sponsors and other interested people about happenings at SSRL. SSRL is a
national synchrotron user facility operated by Stanford University for the
U.S. Department of Energy Office of Basic Energy
Sciences. Additional support for
the structural biology program is provided by
the DOE
Office of Biological and Environmental Research, the NIH
National Center for Research Resources and the NIH Institute for General Medical
Sciences. Additional information about
SSRL and its operation and schedules is available from the SSRL WWW
site.
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