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No need to hammer home the Popeye parallel, so let's get right down to it: there’s a new reason to love spinach. And this new reason is related to the old reason – why your mother insisted you eat it.
Like all leafy greens, spinach is very good for you. Beyond that, the vegetable's intense green is evidence that it can help energy researchers develop a better understanding of the proteins used in photosynthesis, in which plants convert sunlight into nourishment.
“The proteins we study are part of the most efficient system ever built, capable of converting the energy from the sun into chemical energy with an unrivaled 60 percent efficiency,” said Yulia Pushkar, an associate professor of physics at Purdue University involved in an international effort to crack the plant code and create artificial photosynthesis.
Plants use the Sun's energy to convert water and carbon dioxide into oxygen and carbohydrates, which store hydrogen. Developing artificial photosynthesis would lead to methods to convert solar energy into hydrogen-based fuels, which are clean and sustainable.
At Purdue, students are extracting a protein known as Photosystem II, or PSII, from spinach. The extraction process takes two days and requires a specially built laboratory that keeps the spinach cold and in the dark. The next step is to “excite” the proteins with lasers and record changes in the configuration of electrons in their molecules.
“The laser acts as the sun in this experiment,” Pushkar explains. “Once the proteins start working, we use advanced techniques like electron paramagnetic resonance and X-ray spectroscopy to observe how the electronic structure of the molecules change over time as they perform their functions.”
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PSII is needed for photosynthesis to split water molecules into oxygen, electrons and protons. Pushkar says that during this process, part of the protein, called the oxygen-evolving complex, extracts four electrons from PSII as it cycles through five states. So far the team has identified the structures of the first and third states, and published their findings in the journal Nature.
Here's how they do it, according to the leader of the international team, Petra Fromme, a professor of chemistry and biochemistry at Arizona State University: researchers use science's most powerful X-ray laser, called the LCLS, run by the U.S. Department of Energy, which is capable of laser pulses as fast as a femtosecond, or one-quadrillionth of a second.
In a statement to the Purdue University news department, Fromme says, these pulses “record snapshots of the PSII crystals before they explode.” That method allowed the researchers to identify two of the structures thus far.
The job of the Purdue team is to use these results to determine how a plant's electronic configurations change over time. So far, Pushkar's team has been able to do just that with the two states already identified, a major step to gaining a full understanding of using artificial photosynthesis to generate renewable fuels.
By Andy Tully of Oilprice.com
Andy Tully is a veteran news reporter who is now the news editor for Oilprice.com