User Spotlight: Pushing Crystallography to the Extremes at LCLS

July 16, 2012

Arizona State University’s Petra Fromme, a leading researcher in the emerging field of X-ray laser crystallography and an avid musician, has been using SLAC’s Linac Coherent Light Source to study proteins involved in photosynthesis and other important processes.

Her 35-member international research team, which includes groups from ASU, the Max Planck Institute for Medical Research and DESY, both in Germany, and Lawrence Livermore National Laboratory, studies crystallized samples of Photosystems I and II – protein complexes that plants use to convert sunlight into chemical energy. The ultra short, brilliant X-ray pulses at LCLS, measured in femtoseconds, or quadrillionths of a second, allow scientists to determine the detailed structures of complex molecular systems by probing crystallized samples of the molecules with X-rays.

For her latest visit in June, Fromme's group drove to SLAC in a U-Haul truck with all the lab equipment and instruments needed to prepare the tiny crystals at SLAC for use in the experiments. The crystals are very sensitive to light and temperature and otherwise would be damaged in transit.

A viola player, Fromme brought her viola to SLAC during a round of experiments in January 2012. Stopped along the way at a vehicle checkpoint between Arizona and California, the researchers attested that their truck contained two types of instruments – “scientific instruments and musical instruments."

Fromme described her career path in science, her experiments at the LCLS’s CXI instrument and her sideline as a musician.

What is the focus of your latest experiments at LCLS?
‚ÄčPF: Our current experiments are focused on making molecular movies of the water-splitting process in photosynthesis and determining the structures of large membrane protein complexes important to the conversion of sunlight to energy, and to human health.

In the first experiments, we are studying very fast structural changes in crystals of Photosystem II. Photosystem II is a key protein in photosynthesis where light from the sun is converted into chemical energy. This process provides energy for all higher life on Earth and produces all the oxygen in the atmosphere. It requires four light-driven steps to reach the final stage where oxygen is produced.

What we want to unravel are the very fast structural changes, or dynamics, that take place during this process of oxygen evolution. We will do that by making a stop-motion “movie” of the process with at least molecular resolution, and finally at atomic detail. This information is very important for the development of an artificial oxygen-evolving complex – one of the projects my group works on in the DOE-funded Energy Frontier Science Center on Bioinspired Solar Fuel production at ASU.

Describe your scientific background.
PF: I have served as a professor of chemistry and biochemistry at ASU for 10 years, with an affiliate faculty position in physics. I also lead the ASU Center for Membrane Proteins in Infectious Diseases, funded by the National Institutes of Health.

I started my career at the Free University Berlin and received a doctoral degree in chemistry from Technical University Berlin, where I also performed postdoctoral work in physical chemistry.

My research is focused on photosynthesis and the structure and function of large membrane protein complexes. It is a big challenge to unravel at atomic detail how photosynthesis converts light energy into chemical energy. We want to learn from nature by unraveling the mechanisms of the natural system to build an "artificial leaf" that could provide clean, sustainable energy for humankind.

Why did you choose biophysical chemistry?
PF: When I finished high school I originally chose to study biochemistry because I wanted to cure cancer. But while working in university labs as a student, I found out that my real passion was for photosynthesis and biophysical chemistry, a topic that is even more important for life on Earth than cancer. I also realized that I did not want to do research that involves animals. So I moved from the biology side to the physics side.

The science of crystallography is 100 years old. What important contributions do you believe crystallography will make in the next 100 years?
PF: Lawrence Bragg, a crystallography pioneer, and others would have dreamed of being able to look not only at the structure but also the dynamics of protein complexes with more than 200,000 atoms. They may have thought it impossible. Now the goal of "molecular movies" of biological processes at the atomic level might actually be reached for the first time with crystallography at free electron lasers (FELs), which open a new era for the field.

LCLS is the first high-energy FEL in the world and the only site where these experiments can be performed. It allows studies of proteins that are much bigger and much more difficult to crystallize. In addition, we can induce reactions in those proteins by hitting them with light or mixing the crystals with other materials. This opens the field for studying much faster dynamic changes in single protein crystals than ever possible before. I think we are really at the doorstep of a new era.

Describe an interesting hobby.
PF: I have played viola since I was 9. Music has always been a very important part of my life and I played in several orchestras in Berlin before I moved to Arizona. Currently I play in the Tempe Symphony Orchestra and also in a string quartet that meets twice a month.

The best scientific ideas always come to my mind after I play music for an evening. During my group's last visit to LCLS, we were here four weeks. I brought my viola and went back home during a short break to play a rehearsal. My husband, Raimund Fromme, whom I met 33 years ago when we both played in a youth orchestra in Berlin, is also involved with crystallography research and LCLS experiments, and is a bassoon player in the Tempe Symphony Orchestra.