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SSRL Headlines Vol. 11, No. 8  February, 2011


Contents of this Issue:

  1. From the Director of SSRL: DOE Reviews SSRL and Strategic Plan Development Continues
  2. Science Highlight — A Complex Relationship between Active Layer and Output Current in Organic Solar Cells
  3. Science Highlight — An mRNA Processing Complex with an Unusual Choice of Substrate
  4. SSRL Gains New Spectroscopy Capabilities
  5. SLAC Team Ensures Safety of SPEAR3 Upgrade
  6. Public Lectures: Dino-Bird and Microbes Built with Arsenic
  7. Meeting in Washington, D.C.
  8. February Issue of NUFO News Now Online

1.   From the Director of SSRL: DOE Reviews SSRL and Strategic Plan Development Continues

Chi-Chang Kao
Chi-Chang Kao
Earlier this month, SSRL hosted the Department of Energy's tri-annual review of the lightsource. This very important review gave us a chance to showcase what we have accomplished over the last three years, and present our vision and plan for the future in front of our peers and DOE program managers. Thanks to January's very useful Scientific Advisory Committee (SAC), Machine Advisory Committee (MAC) and Users' Executive Committee (UEC) meetings, we were able to incorporate valuable input from these advisory bodies into the DOE review documentation and presentation.

The DOE review went very well based on what we heard from the reviewers both during the review and at the closeout, although the final report will not be available for another two to three months. The reviewers were uniform in their very positive comments on the scientific productivity, legendary user support and technical developments of SSRL, as well as the major steps taken by SLAC over the last three years. In fact, one reviewer stated that, among DOE laboratories that he is aware of, SLAC is the best in making science the highest priority. This is a clear validation of the success of SSRL as a major user facility.

I would like to take this opportunity to acknowledge the effort and teamwork of the SSRL staff, as well as the assistance we received from many in the laboratory, over the last few months. It's been a whirlwind, but a very productive and useful one.

As we continue forward, I again ask for you to share your viewpoint and suggestions for the SSRL strategic plan. Where should we be heading in the coming decade? And what scientific areas are most important for us to consider in our plans? I look forward to hearing from you.

—Chi-Chang Kao

2.  Science Highlight — A Complex Relationship between Active Layer and Output Current in Organic Solar Cells
       (contact: E. Gomez,

Solar power is an important component of our society's future energy portfolio, and organic materials may be the technology that makes solar cells cheap enough for wide-spread implementation.

Currently, organic or plastic solar cells are relatively inexpensive to make, yet they are also relatively inefficient. Researchers from Princeton University and SSRL recently studied the structure of solar cells that were manufactured and processed in different ways to better understand the causes of the inefficiencies.

The experiments, conducted at SSRL Beam Line 11-3, showed a complex relationship between the crystallinity of an organic solar cell's active layer and the cell's output current. Output currents were not directly tied with the crystallinity of the polymer (P3HT) in the active layer, as was expected. Instead, the researchers found that the output currents were correlated with the polymer crystallinity only in solar cells in which the fullerene derivative (PCBM), also contained in the active layer, was locally well organized. These results show that the structure of both components is very important, and should both be considered to increase organic solar cell performance. This work was published in the January 7, 2011 issue of Chemical Communications.

P3HT/PCBM image
Characterization of the P3HT/PCBM structure through X-ray scattering. (a) 2-D GIXD data of a P3HT/PCBM mixture. (b) Device short-circuit current density (JSC) vs. P3HT crystallinity for various P3HT/PCBM samples.

To learn more about this research see the full scientific highlight

3.  Science Highlight — An mRNA Processing Complex with an Unusual Choice of Substrate        (contact: L. Tong,

Messenger RNA, responsible for relaying information from the DNA to the ribosomes, is given a 5' cap and a 3' tail. The 3'-end cleavage and polyadenylation are performed by a large protein complex that includes a scaffolding protein called symplekin.

A research team led by Liang Tong of Columbia University used SSRL Beam Line 9-2 to solve the crystal structure of the N-terminal domain of human symplekin at 1.9 Å resolution as well as the crystal structures of symplekin in complex with other components of the system. The basis of symplekin's structure is seven pairs of anti-parallel a helices, similar to the structures of other scaffolding proteins. The group also discovered how the protein Ssu72 binds to symplekin and that this interaction stimulates Ssu72's phosphatase activity. They noted that Ssu72 prefers an unusual substrate: it binds pSer-Pro peptides in a cis configuration, whereas most proline-directed serine phosphatases act on the trans configuration.

The researchers suggest that Ssu72's trans configuration preference is important for 3'-end processing coordination and transcription regulation. This work was published in the October 7, 2010 issue of Nature.

highlight figure
A Schematic representation of the structure of the human symplekin N-terminal domain (cyan)-Ssu72 (yellow)-CTD phosphopeptide (green) ternary complex.B Electron density for the CTD phosphopeptide at 2.4 Å resolution. The cis peptide bond between pSer5 and Pro6 is clearly visible.

To learn more about this research see the full scientific highlight

4.   SSRL Gains New Spectroscopy Capabilities

40-crystal spectrometer
From left: Tsu-Chien Weng, Dennis Nordlund and Dimosthenis Sokaras with the new 40-crystal spectrometer. (Photo by Brad Plummer.)
A new spectroscopy instrument has been installed on SSRL Beam Line 6-2, and staff scientists are now working to test its various components before offering beam time to users this spring. The setup will expand SSRL capabilities in x-ray Raman and x-ray emission spectroscopy-two techniques used to analyze the organization of electrons in solids, liquids and gases-and keep SSRL positioned as a leading synchrotron user facility.

"This will open up the science to a whole new set of users," said SSRL Staff Scientist Dennis Nordlund, who is part of the team building the instrument. According to Nordlund, the higher intensity and better resolution offered by the x-ray Raman instrument make it a very competitive alternative to soft x-ray spectroscopy. What's more, he says, it overcomes many technical limitations that come with soft x-ray studies, such as the need to operate under a vacuum. Read more at:

SPEAR3 Topoff Safety Poster
Alyssa Prinz, Xiaobiao Huang, Dave Wenger, Johannes Bauer, Carol Morris, John Schmerge, James Liu. (Photo by Brad Plummer. Poster by SLAC Information Management and Portal Solutions.)
5.   SLAC Team Ensures Safety of SPEAR3 Upgrade

Ensuring the safety of SSRL users and staff has been a guiding principle in the ongoing effort to bring the SPEAR3 accelerator up to its design capacity of 500 mA of current. This principle has never been more evident than during the shift to top-off injection last year. This operating mode permits the addition of electrons to the SPEAR3 storage ring while the x-ray beam line injection stoppers remain open-a radical change from past procedure.

"Before top-off, the injection stoppers had to be inserted for all injections," said James Liu, a radiation physicist with SLAC's Radiation Protection Department, which is charged with providing support and oversight for the radiological safety of accelerators, beam lines and experiments. The electrons circulating around the SPEAR3 storage ring, emitting the x-rays needed by SSRL users, require a periodic boost in the form of more electrons, which are "injected" into the ring. More-frequent injections support a higher beam current-more x-rays for user experiments. Read more at:

6.   Public Lectures: Dino-Bird and Microbes Built with Arsenic

On Tuesday, March 22, SSRL Staff Scientist Sam Webb and NASA Astrobiologist Felisa Wolfe-Simon will present the public lecture "Life Redefined: Microbes Built with Arsenic" at 7:30 p.m. in SLAC's Panofsky Auditorium. The lecture will describe the team's research into the first known living organism that appears to incorporate arsenic into the working parts of its cells, replacing phosphorus, an element long thought essential for life. This work challenges the notion that however diverse organisms may be, they are all made of the same elements: carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. More information on attending the public lecture can be found at:

In addition, former SSRL Staff Scientist Uwe Bergmann presented the public lecture "Archaeopteryx: Bringing the Dino-Bird to Life" at SLAC on January 25. For those who could not attend, the lecture is now available online. Additional information about this work can also be found in a January 21 New Scientist article, "Reanimators: Waking the Dino Dead." The article can be accessed at: (subscription required).

7. Meeting in Washington, D.C.       

The management board of, the international group of synchrotron/free electron laser communications and public affairs officers, met last week during the AAAS meeting in Washington, D.C., to discuss new ways to better serve the light source user communities and promote their scientific successes to the media, educators, students and the general public. To better serve its audiences, will be sending out a brief survey at the beginning of May to assess the usage of the site and the digital and media needs of the user community. Visit and give your feedback!

8.   February Issue of NUFO News Now Online       

The February edition of the National User Facility Organization's NUFO News is now available online. The edition features a report on NUFO's educational outreach and a description of an upcoming Capitol Hill user science exhibition.


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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Last Updated: 28 February 2011
Headlines Editor: K. Tuttle