Surprise Discovery Could Revolutionize Solar Energy

This is the experimental setup used to generate femtosecond laser pulses which serve as an ultrafast “flash ” for the camera so that very rapid phenomenon can be filmed. Credit: Simon Gelinas

In a newly published study, researchers from Cambridge’s Cavendish Laboratory detail the surprise discovery that could revolutionize solar energy.

Researchers have been able to tune ‘coherence’ in organic nanostructures due to the surprise discovery of wavelike electrons in organic materials, revealing the key to generating “long-lived charges” in organic solar cells – material that could revolutionize solar energy.

By using an ultrafast camera, scientists say they have observed the very first instants following the absorption of light into artificial yet organic nanostructures and found that charges not only formed rapidly but also separated very quickly over long distances – phenomena that occur due to the wavelike nature of electrons which are governed by fundamental laws of quantum mechanics.

This result surprised scientists as such phenomena were believed to be limited to “perfect” – and expensive – inorganic structures; rather than the soft, flexible organic material believed by many to be the key to cheap, ‘roll-to-roll’ solar cells that could be printed at room temperatures – a very different world from the traditional but costly processing of current silicon technologies.

The study,sheds new light on the mystery mechanism that allows positive and negative charges to be separated efficiently – a critical question that continues to puzzle scientists – and takes researchers a step closer to effectively mimicking the highly efficient ability to harvest sunlight and convert into energy, namely photosynthesis, which the natural world evolved over the course of millennia.

“This is a very surprising result. Such quantum phenomena are usually confined to perfect crystals of inorganic semiconductors, and one does not expect to see such effects in organic molecules – which are very disordered and tend to resemble a plate of cooked spaghetti rather than a crystal,” said Dr Simon Gélinas, from Cambridge’s Cavendish Laboratory, who led the research with colleagues from Cambridge as well as the University of California in Santa Barbara.

During the first few femtoseconds (one millionth of one billionth of a second) each charge spreads itself over multiple molecules rather than being localized to a single one. This phenomenon, known as spatial coherence, allows a charge to travel very quickly over several nanometers and escape from its oppositely charged partner – an initial step which seems to be the key to generating long-lived charges, say the researchers. This can then be used to generate electricity or for chemical reactions.

By carefully engineering the way molecules pack together, the team found that it was possible to tune the spatial coherence and to amplify – or reduce – this long-range separation. “Perhaps most importantly the results suggest that because the process is so fast it is also energy efficient, which could result in more energy out of the solar cell,” said Dr Akshay Rao, a co-author on the study from the Cavendish Laboratory.

Dr Alex Chin, who led the theoretical part of the project, added that, if you look beyond the implications of the study for organic solar cells, this is a clear demonstration of “how fundamental quantum-mechanical processes, such as coherence, play a crucial role in disordered organic and biological systems and can be harnessed in new quantum technologies”.

The work at Cambridge forms part of a broader initiative to harness high tech knowledge in the physics sciences to tackle global challenges such as climate change and renewable energy. This initiative is backed by both the UK Engineering and Physical Sciences Research Council (EPSRC) and the Cambridge Winton Program for the Physics of Sustainability. The work at the University of California in Santa Barbara was supported by the Center for Energy Efficient Materials, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award #DC0001009.

Publication: Simon Gélinas, et al., “Ultrafast Long-Range Charge Separation in Organic Semiconductor Photovoltaic Diodes,” Science, 2013; DOI: 10.1126/science.1246249

Source: University of Cambridge

Image: Simon Gelinas

Inactivating AGPS Enzyme Reduces Tumor Growth, Cripples Cancer Cells

Illustration of an aggressive cancer cell. Image by O’Reilly Science Art

In a newly published study, researchers tested the effects of reducing ether lipids on human skin cancer cells and primary breast tumors, finding that inactivating an enzyme critical to the formation of ether lipids substantially reduced the aggressiveness of the cancer cells.

Berkeley — Knocking out a single enzyme dramatically cripples the ability of aggressive cancer cells to spread and grow tumors, offering a promising new target in the development of cancer treatments, according to a new study by researchers at the University of California, Berkeley.

The paper, sheds new light on the importance of lipids, a group of molecules that includes fatty acids and cholesterol, in the development of cancer.

Researchers have long known that cancer cells metabolize lipids differently than normal cells. Levels of ether lipids – a class of lipids that are harder to break down – are particularly elevated in highly malignant tumors, although the nature of that correlation has been unclear for decades.

“Cancer cells make and use a lot of fat and lipids, and that makes sense because cancer cells divide and proliferate at an accelerated rate, and to do that, they need lipids, which make up the membranes of the cell,” said study principal investigator Daniel Nomura, assistant professor in UC Berkeley’s Department of Nutritional Sciences and Toxicology. “Lipids have a variety of uses for cellular structure, but what we’re showing with our study is that lipids can also send signals that fuel cancer growth.”

In the study, Nomura and his team tested the effects of reducing ether lipids on human skin cancer cells and primary breast tumors. They targeted an enzyme, alkylglycerone phosphate synthase, or AGPS, known to be critical to the formation of ether lipids.

The researchers first confirmed that AGPS expression increased when normal cells turned cancerous. They then found that inactivating AGPS substantially reduced the aggressiveness of the cancer cells.

“The cancer cells were less able to move and invade,” said Nomura.

The researchers also compared the impact of disabling the AGPS enzyme in mice that had been injected with cancer cells.

“Among the mice that had the AGPS enzyme inactivated, the tumors were nonexistent,” said Nomura. “The mice that did not have this enzyme disabled rapidly developed tumors.”

The researchers determined that inhibiting AGPS expression depleted the cancer cells of ether lipids. They also found that AGPS altered levels of other types of lipids important to the ability of the cancer cells to survive and spread, including prostaglandins and acyl phospholipids.

“The effect on other lipids was unexpected and previously unknown,” said study lead author Daniel Benjamin, doctoral student in the Nomura Research Group. “Other studies have investigated specific lipid signaling pathways, but what makes AGPS stand out as a treatment target is that the enzyme seems to simultaneously regulate multiple aspects of lipid metabolism important for tumor growth and malignancy.”

Future steps include the development of AGPS inhibitors for use in cancer therapy, said Nomura.

“This study sheds considerable light on the important role that AGPS plays in ether lipid metabolism in cancer cells, and it suggests that inhibitors of this enzyme could impair tumor formation,” said Benjamin Cravatt, professor and chair of chemical physiology at The Scripps Research Institute, who is not part of the UC Berkeley study. Cravatt is an expert in the role enzymes play in human diseases.

Other study co-authors include Kunxin Luo, UC Berkeley professor of molecular and cell biology and faculty scientist at the Lawrence Berkeley National Laboratory.

The National Institutes of Health and the Searle Scholar Foundation helped support this research.

Publication: Daniel I. Benjamin, et al., “Ether lipid generating enzyme AGPS alters the balance of structural and signaling lipids to fuel cancer pathogenicity,” PNAS, 2013; doi: 10.1073/pnas.1310894110

Source: Sarah Yang, UC Berkeley News

Image: O’Reilly Science Art

Engineers Convert Yeast Cells into Biofuel

Left: Starting cells with around 15 percent lipid content. Right: Engineered cells with nearly 90 percent lipid content.

Using genetically engineered yeast cells and ordinary table sugar, engineers from the Cockrell School of Engineering developed a new biofuel.

Austin, Texas — Researchers at The University of Texas at Austin’s Cockrell School of Engineering have developed a new source of renewable energy, a biofuel, from genetically engineered yeast cells and ordinary table sugar. This yeast produces oils and fats, known as lipids, that can be used in place of petroleum-derived products.

Assistant professor Hal Alper, in the Cockrell School’s McKetta Department of Chemical Engineering, along with his team of students, created the new cell-based platform. Given that the yeast cells grow on sugars, Alper calls the biofuel produced by this process “a renewable version of sweet crude.”

The researchers’ platform produces the highest concentration of oils and fats reported through fermentation, the process of culturing cells to convert sugar into products such as alcohol, gases or acids.

The UT Austin research team was able to rewire yeast cells to enable up to 90 percent of the cell mass to become lipids, which can then be used to produce biodiesel.

“To put this in perspective, this lipid value is approaching the concentration seen in many industrial biochemical processes,” Alper said. “You can take the lipids formed and theoretically use it to power a car.”

Since fatty materials are building blocks for many household products, this process could be used to produce a variety of items made with petroleum or oils — from nylon to nutrition supplements to fuels. Biofuels and chemicals produced from living organisms represent a promising portion of the renewable energy market. Overall, the global biofuels market is expected to double during the next several years, going from $82.7 billion in 2011 to $185.3 billion in 2021.

“We took a starting yeast strain of Yarrowia lipolytica, and we’ve been able to convert it into a factory for oil directly from sugar,” Alper said. “This work opens up a new platform for a renewable energy and chemical source.”

The biofuel the researchers formulated is similar in composition to biodiesel made from soybean oil. The advantages of using the yeast cells to produce commercial-grade biodiesel are that yeast cells can be grown anywhere, do not compete with land resources and are easier to genetically alter than other sources of biofuel.

“By genetically rewiring Yarrowia lipolytica, Dr. Alper and his research group have created a near-commercial biocatalyst that produces high levels of bio-oils during carbohydrate fermentation,” said Lonnie O. Ingram, director of the Florida Center for Renewable Chemicals and Fuels at the University of Florida. “This is a remarkable demonstration of the power of metabolic engineering.”

So far, high-level production of biofuels and renewable oils has been an elusive goal, but the researchers believe that industry-scale production is possible with their platform.

In a large-scale engineering effort spanning over four years, the researchers genetically modified Yarrowia lipolytica by both removing and overexpressing specific genes that influence lipid production. In addition, the team identified optimum culturing conditions that differ from standard conditions. Traditional methods rely on nitrogen starvation to trick yeast cells into storing fat and materials. Alper’s research provides a mechanism for growing lipids without nitrogen starvation. The research has resulted in a technology for which UT Austin has applied for a patent.

“Our cells do not require that starvation,” Alper said. “That makes it extremely attractive from an industry production standpoint.”

The team increased lipid levels by nearly 60-fold from the starting point.

At 90 percent lipid levels, the platform produces the highest levels of lipid content created so far using a genetically engineered yeast cell. To compare, other yeast-based platforms yield lipid content in the 50 to 80 percent range. However, these alternative platforms do not always produce lipids directly from sugar as the UT Austin technology does.

Alper and his team are continuing to find ways to further enhance the lipid production levels and develop new products using this engineered yeast.

This research was funded by the Office of Naval Research Young Investigator Program, the DuPont Young Professor Grant and the Welch Foundation under grant F-1753.

Publication: John Blazeck, et al., “Harnessing Yarrowia lipolytica lipogenesis to create a platform for lipid and biofuel production,” Nature Communications 5, Article number: 3131; doi:10.1038/ncomms4131

Source: University of Texas at Austin’s Cockrell School of Engineering

Image: University of Texas at Austin’s Cockrell School of Engineering