Using European XFEL to shed light on photosynthesis

First membrane protein studied at European XFEL

In a paper now published in Nature Communications an international group of scientists show that the fast X-ray pulse rate produced by the European XFEL can be used to study the structure of membrane proteins such as those involved in the process of photosynthesis. These results open up eagerly awaited experimental opportunities for scientists studying these types of proteins.

Large proteins and protein complexes are difficult to study with traditional structural biology approaches. Large protein complexes, such as those that sit across cell membranes and regulate traffic in and out of cells, are difficult to crystalize and generally only produce small crystals that are hard to analyse. The extremely fast X-ray pulses generated by European XFEL now enable scientists to collect large amounts of data from a stream of small crystals to develop detailed models of the 3D structure of these proteins.

>Read more on the European XFEL website

Image (extract, full illustration in the article): Graphic shows the basic design of a serial femtosecond crystallography experiment at European XFEL. X-ray bursts strike crystallized samples resulting in diffraction patterns that can be reassembled into detailed images.
Credit: Shireen Dooling for the Biodesign Institute at ASU

Research on how light-harvesting bacteria toggle off and on

The results could have long-range implications for artificial photosynthesis and optogenetics—the use of light to selectively activate biological processes.

Cyanobacteria are water-dwelling microbes capable of absorbing sunlight and converting it into chemical energy through photosynthesis. Long ago, ancient versions of these bacteria were incorporated into plant cells, where they eventually evolved into chloroplasts, the organelles responsible for carrying out photosynthesis in green plants. Today, in seeking to develop artificial photosynthesis to harness the sun’s abundant energy, scientists look to cyanobacteria to better understand the nuts and bolts of how natural photosynthesis works.

Cyanobacterial “off switch”

One topic of interest is how cyanobacteria respond to too much light. If a sunlight-harvesting system becomes overloaded with absorbed solar energy, it most likely will suffer some form of damage. Nature has solved the problem in cyanobacteria through a protective mechanism—an energy-quenching “off switch” in which excess solar energy is safely dissipated as heat.

>Read more on the Advanced Light Source at BNL

Illustration: X-ray footprinting provides time-resolved information about where key conformational changes occur. On the left is the overall OCP structure. The two structures on the right highlight local areas with increasing protein packing over time (blue shading) and areas with decreasing protein packing over time (red shading). The changes in accessibility are initiated by the movement of the carotenoid molecule (magenta chain).

A timely solution for the photosynthetic oxygen evolving clock

XFEL Hub collaboration reveals the intermediates of the photosynthetic water oxidation clock

A large international collaborative effort aided by the XFEL Hub at Diamond Light Source has generated the most detailed time-resolved studies to date of a key protein involved in photosynthesis. The pioneering work, recently published in Nature, shows how photosystem II harnesses light energy to produce oxygen – insights that could direct a next generation of photovoltaic cells. 
>Read more on the Diamond Light Source website

Image: this figure is issued from a video you can watch here.

Researchers create most complete high-res atomic movie of photosynthesis to date

In a major step forward, SLAC’s X-ray laser captures all four stable states of the process that produces the oxygen we breathe, as well as fleeting steps in between. The work opens doors to understanding the past and creating a greener future.

Despite its role in shaping life as we know it, many aspects of photosynthesis remain a mystery. An international collaboration between scientists at SLAC National Accelerator Laboratory, Lawrence Berkeley National Laboratory and several other institutions is working to change that. The researchers used SLAC’s Linac Coherent Light Source (LCLS) X-ray laser to capture the most complete and highest-resolution picture to date of Photosystem II, a key protein complex in plants, algae and cyanobacteria responsible for splitting water and producing the oxygen we breathe. The results were published in Nature today.

Explosion of life

When Earth formed about 4.5 billion years ago, the planet’s landscape was almost nothing like what it is today. Junko Yano, one of the authors of the study and a senior scientist at Berkeley Lab, describes it as “hellish.” Meteors sizzled through a carbon dioxide-rich atmosphere and volcanoes flooded the surface with magmatic seas.
Over the next 2.5 billion years, water vapor accumulating in the air started to rain down and form oceans where the very first life appeared in the form of single-celled organisms. But it wasn’t until one of those specks of life mutated and developed the ability to harness light from the sun and turn it into energy, releasing oxygen molecules from water in the process, that Earth started to evolve into the planet it is today. This process, oxygenic photosynthesis, is considered one of nature’s crown jewels and has remained relatively unchanged in the more than 2 billion years since it emerged.

>Read more on the SLAC website (for LCLS)
>Read also the article on the Berkeley website (for ALS)

Image: Using SLAC’s X-ray laser, researchers have captured the most complete high-res atomic movie to date of Photosystem II, a key protein complex in plants, algae and cyanobacteria responsible for splitting water and producing the oxygen we breathe.
Credit: Gregory Stewart, SLAC National Accelerator Laboratory)

Insight into catalysis through novel study of X-ray absorption spectroscopy

An international team has made a breakthrough at BESSY II.

For the first time, they succeeded in investigating electronic states of a transition metal in detail and drawing reliable conclusions on their catalytic effect from the data. These results are helpful for the development of future applications of catalytic transition-metal systems. The work has now been published in Chemical Science, the Open Access journal of the Royal Society of Chemistry.

Many important processes in nature depend on catalysts, which are atoms or molecules that facilitate a reaction, but emerge from it themselves unchanged. One example is photosynthesis in plants, which is only possible with the help of a protein complex comprising four manganese atom sites at its centre. Redox reactions, as they are referred to, often play a pivotal role in these types of processes. The reactants are reduced through uptake of electrons, or oxidized through their release. Catalytic redox processes in nature and industry often only succeed thanks to suitable catalysts, where transition metals supply an important function.

>Read more about on the BESSY II at HZB website

Image: Manganese compounds also play a role as catalysts in photosynthesis.
Credit: HZB

Magnetic trick triples the power of SLAC’s X-ray laser

The new technique will allow researchers to observe ultrafast chemical processes previously undetectable at the atomic scale.

Scientists at the Department of Energy’s SLAC National Accelerator Laboratory have discovered a way to triple the amount of power generated by the world’s most powerful X-ray laser. The new technique, developed at SLAC’s Linac Coherent Light Source (LCLS), will enable researchers to observe the atomic structure of molecules and ultrafast chemical processes that were previously undetectable at the atomic scale.

The results, published in a Jan. 3 study in Physical Review Letters (PRL), will help address long-standing mysteries about photosynthesis and other fundamental chemical processes in biology, medicine and materials science, according to the researchers.

“LCLS produces the world’s most powerful X-ray pulses, which scientists use to create movies of atoms and molecules in action,” said Marc Guetg, a research associate at SLAC and lead author of the PRL study. “Our new technique triples the power of these short pulses, enabling higher contrast.”

>Read more on the LCSL website

Picture: The research team, from left: back row, Yuantao Ding, Matt Gibbs, Nora Norvell, Alex Saad, Uwe Bergmann, Zhirong Huang; front row, Marc Guetg and Timothy Maxwell.
Credit: Dawn Harmer/SLAC

 

Fuel from the sun: insight into electrode performance

Soft x-ray studies of hematite electrodes—potentially key components in producing fuel from sunlight—revealed the material’s electronic band positions under realistic operating conditions.

In photosynthesis, plants use sunlight to split water into oxygen and hydrogen. The oxygen is released into the atmosphere, and the hydrogen is used to produce molecules—such as carbohydrates and sugars—that store energy in chemical bonds. Such compounds constitute the original feedstocks for subsequent forms of fuel consumed by society.

Photoelectrochemical (PEC) water splitting is a form of “artificial” photosynthesis that uses semiconductor material, rather than organic plant material, to facilitate water splitting. Electrodes made of semiconductor material are immersed in an electrolyte, with sunlight driving the water-splitting process. The performance of such PEC devices is largely determined at the interface between the photoanode (the electrode at which light gets absorbed) and the electrolyte.

>Read more on the ALS webpage

Photo: Roy Kaltschmidt