New biocatalyst could more efficiently split water molecules

Experiment carried out on Sirius shed light on reaction fundamental to the production of hydrogen fuel

A recent experiment at Sirius, the Brazilian synchrotron light source at the Brazilian Center for Research in Energy and Materials (CNPEM) in Campinas, São Paulo (see Pesquisa FAPESP issue 269) showed how a certain biological catalyst can more efficiently split water molecules (H2O) using electrolysis. This reaction, an electrochemical process that uses electricity to break down water into the elements that comprise it, is very significant because it produces not only oxygen but also hydrogen, considered the fuel of the future by many specialists because it does not emit any polluting gases when it is utilized (see Pesquisa FAPESP issue 314).

“We discovered that when some enzymes present in nature like bilirubin oxidase (BOD) are manipulated in the lab, they can accelerate the reaction to split water,” states chemist Frank Nelson Crespilho, a professor at the University of São Paulo’s São Carlos Institute of Chemistry (IQSC-USP) who led the study. “We didn’t know why this happened; thanks to new equipment developed specifically for Sirius, we were able to observe how this enzyme, BOD, behaves during the process of oxidation in water. We found that the copper atoms within it are relevant to this reaction.”

Crespilho expects this advance to pave the way for science to get inspiration from the part of the enzyme that accelerated the reaction. “It is important for us to recognize the important regions of BOD, since today synthetic chemists that work in materials production can copy and synthesize this part of the enzyme in the laboratory. This will make the catalyst much more affordable, with a much broader range of potential applications,” he adds. Most of the catalysts used in this process utilize noble metals like platinum and iridium, making large-scale application unfeasible due to the cost involved. An article describing the experiment written by Crespilho’s team, which includes the researchers Graziela Sedenho, Rafael Colombo, Thiago Bertaglia, and Jessica Pacheco, was published in October in the journal Advanced Energy Materials. Scientists from the Brazilian Synchrotron Light National Laboratory (LNLS) also participated in the study.

Read more on the LNLS website

Image: Researcher manipulates electrochemical cell used in experiment

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.

Unraveling the Complexities of Auto-Oxidation

Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how important bioinorganic electron transfer systems operate. Using a combination of very different, time-resolved measurement methods at DESY’s X-ray source PETRA III and other facilities, the scientists were able to show that so-called pre-distorted states can speed up photochemical reactions or make them possible in the first place. The group headed by Sonja Herres-Pawlis from the RWTH Aachen University  Michael Rübhausen from the University of Hamburg and Wolfgang Zinth from Munich’s Ludwig Maximilian University, is presenting its findings in the journal Nature Chemistry.

The scientists had studied the pre-distorted, “entatic” state using a model system. An entatic state is the term used by chemists to refer to the configuration of a molecule in which the normal arrangement of the atoms is modified by external binding partners such that the energy threshold for the desired reaction is lowered, resulting in a higher speed of reaction. One example of this is the metalloprotein plastocyanin, which has a copper atom at its centre and is responsible for important steps in the transfer of electrons during photosynthesis. Depending on its oxidation state, the copper atom either prefers a planar configuration, in which all the surrounding atoms are arranged in the same plane (planar geometry), or a tetrahedral arrangement of the neighbouring ligands. However the binding partner in the protein forces the copper atom to adopt a sort of intermediate arrangement. This highly distorted tetrahedron allows a very rapid shift between the two oxidation states of the copper atom.

>Read more on the PETRA III website

Image Caption: Entatic state model complexes optimize the energies of starting and final configuration to enable fast reaction rates (illustrated by the hilly ground). The work demonstrates that the entatic state principle can be used to tune the photochemistry of copper complexes.
Credit: RWTH Aachen, Sonja Herres-Pawlis