Previous Editions__________________________________________________________________________SSRL Headlines Vol. 10, No. 9 March, 2010__________________________________________________________________________
Contents of this Issue:
A team led by scientists from SLAC and Lawrence Berkeley National Laboratory
used SSRL Beam Line 6-2 to directly observe the oxygen x-ray emission signal
from the oxygen-evolving complex in PSII. They subjected concentrated spinach
samples to x-ray emission spectroscopy (XES), and differentiated the signal of
the few oxygen atoms bound to manganese in the oxygen-evolving complex versus
the multitude of oxygen atoms in the surrounding protein. They observed changes
to the bound-oxygen spectral signature depending on the type of binding using a
series of model compounds.
In follow-up experiments, the researchers are trying to follow the
water-splitting reaction using the x-ray emission of oxygen in the catalytic
active site of PSII. This research was published in the January 18 issue of
Angewandte Chemie.
To learn more about this research see the full scientific highlight
A group led by researcher Sheryl Tsai of the University of California at
Irvine, in collaboration with the Townsend lab of The Johns Hopkins University,
used SSRL Beam Line 9-2 to solve two crystal structures of the "product
template" (PT) domain that is crucial for aflatoxin formation in the molds. One
structure shows a linear substrate analog bound in the active site, while the
other shows an intermediate analog. When analyzed in light of the biochemical
data, these aflatoxin-PT structures revealed, for the first time, how PT folds
an incoming linear carbon chain called a polyketide to form two aflatoxin rings
in an amazing feat of origami.
The researchers proposed that understanding how aflatoxin is made will lead to
an understanding of how to prevent it and drastically reduce terminal illness
in developing countries. The aflatoxin mechanism can also be applied to other
moldy toxins. This research is published in the October 22, 2009 issue of
Nature.
To learn more about this research see the full scientific highlight
By recording how SSRL's x-ray beam scattered off a flowing jet of water, lead
author Ling Fu, a postdoc at the Centre National de la Recherche Scientifique
in France, and SLAC colleagues Arthur Bienenstock and Sean Brennan were able to
determine the distances between the water molecules in the jet. As recent
models predicted, they saw molecules 0.28 and 0.45 nanometers apart. These
measurements confirm the current commonly accepted model, which describes
liquid water as a group of water molecules held together in tetrahedral shapes,
with the molecule at the center of the tetrahedron separated from four others
at the shorter distance and each of these four molecules separated from one
another at the longer distance.
Yet the researchers saw some molecules at a third distance as well: 0.34
nanometers. The existence of this third separation length, though not included
in the current model, was first seen in 1938. Additional experiments in the
1960s and 1970s first confirmed, but later rejected, that this length exists,
concluding that its detection was due to shortcomings in the analysis. As a
result, models including this intermediate distance fell out of
favor—until
now. Read more at:
The SSRL Scientific Advisory Committee met March 29-30 to review and advise
management on current and proposed programs at SSRL. The meeting began with a
talk by SSRL Acting Director Piero Pianetta on operations and strategic
planning. His overall facility update was followed by an overview of SSRL's
Structural Molecular Biology program by Britt Hedman. Kelly Gaffney, Mike
Toney, Tom Rabedeau, Aaron Lindenberg and Donghui Lu followed with in-depth
talks on current and future developments in specific areas.
The lectures were established in memory of Nobel Prize-winning physicist Robert
Hofstadter, who served on the physics faculty from 1950 until his death in
1990. Both talks are free and open to the public.
Stöhr joined Stanford and SLAC in January 2000 as a professor of Photon Science
after spending nearly 15 years at the IBM Almaden Research Center. He was the
director of the Stanford Synchrotron Radiation Lightsource at SLAC before
becoming director of LCLS, which is the world's first x-ray laser. Read more
about lecture schedule and topics at:
Registration is now open for the 5th Annual SSRL SRXAS School to be hosted by
SSRL at SLAC June 1-3, 2010. This school will provide a practical users' guide
to planning and conducting scattering measurements at SSRL beam lines. The
school will cover important techniques, including surface and thin-film
scattering, powder diffraction, in-situ x-ray scattering, and amorphous
materials. It will cover topics that are not commonly addressed in text books
or class lectures, but are typically obtained only through on-the-experiment
training. Modern synchrotron-based x-ray scattering techniques offer the
ability to probe nano- and atomic-scale structures and order/disorder
relationships that critically govern the properties of advanced technological
and environmental materials. Good planning and a working knowledge of beam
lines, in addition to techniques, are keys to conducting successful SR-XRS
measurements. The goal of the school is to provide this knowledge.
Register at:
https://www-ssrl.slac.stanford.edu/conferences/workshops/srxas2010/
See 2009 Meeting Report at:
VUVX2010 will take place at the University of British Columbia, Vancouver, BC,
Canada from 11-16 July 2010. The abstract deadline is 16 April 2010 and early
registration closes 14 May 2010.
This meeting will bring together scientists from countries all over the world
developing new synchrotron, laser, or plasma-based sources of electromagnetic
radiation in the vacuum ultraviolet (VUV), soft x-ray and hard x-ray regions,
and exploring novel applications of these sources. First results from the new
Linear Coherent Light Source (LCLS, Stanford) will be highlighted, along with
results from the Canadian Light Source (CLS), Canada's third generation
synchrotron. There will be an exciting program with outstanding plenary and
invited speakers in 3rd and 4th generation synchrotron science (e.g. Alessandra
Lanzara, John Rehr, Henry Chapman) and also in higher harmonic generation and
attosecond laser science (Ferenc Krausz, Majed Chergui, Akiyoshi Hishikawa). In
addition Paul Corkum will give a general interest lecture to the conference and
the general public ("Catching Electrons with Light"). A special awards session
will feature presentations from the winners of the newly inaugurated VUVX
mid-career and student awards. PhD students may be interested in competing for
the VUVX student award, which provides free registration, $1000 toward
expenses, and a 20-minute podium talk. To be considered for the student award,
the students MUST submit an extended abstract and other information to the
awards chair, Chuck Fadley before April 16. Further details are available on
the student prize page of the VUVX2010 web site.
There will also be a workshop (July 10-11): Quantitative Analysis of X-ray
Absorption Spectra, and two satellite meetings New Science with Resonant
Elastic and Inelastic X-ray Scattering at the University of Saskatchewan,
Saskatoon, SK, Canada (July 8-9), chair: Alex Moewes and Ultrafast VUV and
X-ray science at SLAC, Stanford, CA, USA (July 19-20), chair: John Bozek. For
further information please see the conference web site at:
http://www.vuvx2010.ca
Proteins serve as the tiny gears-and also transport tubes, conveyor belts and
more-that keep living cells ticking. This tiny machinery is too small to see
with visible light, so researchers rely on the short wavelength of x-rays to
catch a glimpse of protein shapes and, from that, their likely functions. As
the x-rays ripple by, the sample molecules disturb, or diffract them, creating
a pattern that reveals the molecules' shape. But it takes a bright beam to
create a clear diffraction pattern. The exposure can damage samples and
introduce noise into already subtle data.
"Radiation damage is really a serious problem when you use very intense x-ray
beams on small and weakly diffracting samples, like protein crystals," said
SLAC researcher Ana Gonzalez. Read more at: http://today.slac.stanford.edu/feature/2010/smb-xray-damage-wkshop.asp
Beam Time Requests for the June to July 26 macromolecular crystallography
scheduling period are due April 20. Submit requests via the user portal at:
New X-ray/VUV proposals are due June 1 for beam time starting in fall 2010.
Please note that our current experimental run ends July 26, 2010. We plan to
resume user operations in late November or the beginning of December 2010.
In this next call for proposals, the world's research community is invited to
submit scientific proposals for experiments to be carried out ~March-June 2011.
During this period, the AMO, SXR, XPP and CXI instruments will be operational.
We have demonstrated FEL operations over the energy range 540 eV to 10 keV, and
we expect to be able to offer an energy down to 520 eV with the LCLS
fundamental for the Spring 2011 run. Typically, the LCLS delivers about 2 mJ
per pulse in the fundamental. Further, LCLS will deliver photons up to 20 keV
from a second harmonic afterburner but reduced by roughly an order of magnitude
in photon number. The pulse length can be tuned from 70-300 fs. Additionally,
shorter pulses (10-40 fs) with reduced pulse energy are also available. The
maximum repetition rate of the x-ray flashes is expected to be 120 Hz. For more
information, see:
http://lcls.slac.stanford.edu/Article.aspx?article_id=178
__________________________________________________________________________
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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