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

Influence of protons on water molecules

How hydrogen ions or protons interact with their aqueous environment has great practical relevance, whether in fuel cell technology or in the life sciences. Now, a large international consortium at the X-ray source BESSY II has investigated this question experimentally in detail and discovered new phenomena. For example, the presence of a proton changes the electronic structure of the three innermost water molecules, but also has an effect via a long-range field on a hydrate shell of five other water molecules.

Excess protons in water are complex quantum objects with strong interactions with the dynamic hydrogen bond network of the liquid. These interactions are surprisingly difficult to study. Yet so-called proton hydration plays a central role in energy transport in hydrogen fuel cells and in signal transduction in transmembrane proteins. While the geometries and stoichiometries have been extensively studied both in experiments and in theory, the electronic structure of these specific hydrated proton complexes remains a mystery.

A large collaboration of groups from the Max Born Institute, the University of Hamburg, Stockholm University, Ben Gurion University and Uppsala University has now gained new insights into the electronic structure of hydrated proton complexes in solution.

Using the novel flatjet technology, they performed X-ray spectroscopic measurements at BESSY II and combined them with infrared spectral analysis and calculations. This allowed them to distinguish between two main effects: Local orbital interactions determine the covalent bond between the proton and neighbouring water molecules, while orbital energy shifts measure the strength of the proton’s extended electric field.

Read more on the HZB website

Image: The spectral fingerprints of water molecules could be studied at BESSY II. The result: the electronic structure of the three innermost water molecules in an H7O3+ complex is drastically changed by the proton. In addition, the first hydrate shell of five other water molecules around this inner complex also changes, which the proton perceives via its long-range electric field.

Credit: © MBI

X-ray laser reveals how radiation damage arises


An international research team has used the SQS instrument at the European XFEL to gain new insights into how radiation damage occurs in biological tissue. The study reveals in detail how water molecules are broken apart by high-energy radiation, creating potentially hazardous electrically charged ions, which can go on to trigger harmful reactions in the organism. The team led by Maria Novella Piancastelli and Renaud Guillemin from the Sorbonne in Paris, Ludger Inhester from DESY and Till Jahnke from European XFEL presents its observations and analyses in the scientific journal Physical Review X.

Since water is present in every known organism, the so-called photolysis of water is often the starting point for radiation damage. “However, the chain of reactions that can be triggered in the body by high-energy radiation is still not fully understood,” explains Inhester. “For example, even just observing the formation of individual ions and radicals in water when high-energy radiation is absorbed is already very difficult.”

Read more on the XFEL website

Image: After the absorption of an X-ray photon, the water molecule can bend up so far that after only about ten femtoseconds (quadrillionths of a second) both hydrogen atoms (grey) are facing each other, with the oxygen atom (red) in the middle. This motion can be studied by absorbing a second X-ray photon.

Credit: DESY, Ludger Inhester

Scientists capture a ‘quantum tug’ between neighbouring water molecules

The work sheds light on the web of hydrogen bonds that gives water its strange properties, which play a vital role in many chemical and biological processes.

Water is the most abundant yet least understood liquid in nature. It exhibits many strange behaviors that scientists still struggle to explain. While most liquids get denser as they get colder, water is most dense at 39 degrees Fahrenheit, just above its freezing point. This is why ice floats to the top of a drinking glass and lakes freeze from the surface down, allowing marine life to survive cold winters. Water also has an unusually high surface tension, allowing insects to walk on its surface, and a large capacity to store heat, keeping ocean temperatures stable.

Now, a team that includes researchers from the Department of Energy’s SLAC National Accelerator Laboratory, Stanford University and Stockholm University in Sweden have made the first direct observation of how hydrogen atoms in water molecules tug and push neighbouring water molecules when they are excited with laser light. Their results, published in Nature today, reveal effects that could underpin key aspects of the microscopic origin of water’s strange properties and could lead to a better understanding of how water helps proteins function in living organisms.

Read more on the LCLS website

Image: For these experiments, the research team (left to right: Xiaozhe Shen, Pedro Nunes, Jie Yang and Xijie Wang) used SLAC’s MeV-UED, a high-speed “electron camera” that uses a powerful beam of electrons to detect subtle molecular movements in samples.

Credit: Dawn Harmer/SLAC National Accelerator Laboratory