Chemists Synthesize Artificial Cell Membrane

Neal Devaraj watches as undergraduate student Weilong Li works on a next step in their quest to create an entirely artificial cell. (Credit: Image courtesy of University of California - San Diego)

Chemists have taken an important step in making artificial life forms from scratch. Using a novel chemical reaction, they have created self-assembling cell membranes, the structural envelopes that contain and support the reactions required for life.

Neal Devaraj, assistant professor of chemistry at the University of California, San Diego, and Itay Budin, a graduate student at Harvard University, report their success in theJournal of the American Chemical Society.

"One of our long term, very ambitious goals is to try to make an artificial cell, a synthetic living unit from the bottom up -- to make a living organism from non-living molecules that have never been through or touched a living organism," Devaraj said. "Presumably this occurred at some point in the past. Otherwise life wouldn't exist."

By assembling an essential component of earthly life with no biological precursors, they hope to illuminate life's origins.

"We don't understand this really fundamental step in our existence, which is how non-living matter went to living matter," Devaraj said. "So this is a really ripe area to try to understand what knowledge we lack about how that transition might have occurred. That could teach us a lot -- even the basic chemical, biological principles that are necessary for life."

Molecules that make up cell membranes have heads that mix easily with water and tails that repel it. In water, they form a double layer with heads out and tails in, a barrier that sequesters the contents of the cell.

Devaraj and Budin created similar molecules with a novel reaction that joins two chains of lipids. Nature uses complex enzymes that are themselves embedded in membranes to accomplish this, making it hard to understand how the very first membranes came to be.

"In our system, we use a sort of primitive catalyst, a very simple metal ion," Devaraj said. "The reaction itself is completely artificial. There's no biological equivalent of this chemical reaction. This is how you could have a de novoformation of membranes."

They created the synthetic membranes from a watery emulsion of an oil and a detergent. Alone it's stable. Add copper ions and sturdy vesicles and tubules begin to bud off the oil droplets. After 24 hours, the oil droplets are gone, "consumed" by the self-assembling membranes.

Although other scientists recently announced the creation of a "synthetic cell," only its genome was artificial. The rest was a hijacked bacterial cell. Fully artificial life will require the union of both an information-carrying genome and a three-dimensional structure to house it.

The real value of this discovery might reside in its simplicity. From commercially available precursors, the scientists needed just one preparatory step to create each starting lipid chain.

"It's trivial and can be done in a day," Devaraj said. "New people who join the lab can make membranes from day one."

The National Institute of Biomedical Imaging and Bioengineering supported this work. UC San Diego has filed a patent application on this discovery.

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The above story is reprinted from materials provided byUniversity of California - San Diego. The original article was written by Susan Brown.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Journal Reference:

1. Itay Budin, Neal K. Devaraj. Membrane Assembly Driven by a Biomimetic Coupling Reaction. Journal of the American Chemical Society, 2012; 134 (2): 751 DOI:10.1021/ja2076873

New Material to Remove Radioactive Gas from Spent Nuclear Fuel

This illustration of a metal-organic framework, or MOF, shows the metal center bound to organic molecules. Each MOF has a specific framework determined by the choice of metal and organic. Sandia chemists identified a MOF whose pore size and high surface area can separate and trap radioactive iodine molecules from a stream of spent nuclear fuel. (Credit: Image courtesy of Sandia National Laboratories)

Science Daily  — Research by a team of Sandia chemists could impact worldwide efforts to produce clean, safe nuclear energy and reduce radioactive waste.

The discovery could be applied to nuclear fuel reprocessing or to clean up nuclear reactor accidents. A characteristic of nuclear energy is that used fuel can be reprocessed to recover fissile materials and provide fresh fuel for nuclear power plants. Countries such as France, Russia and India are reprocessing spent fuel.The Sandia researchers have used metal-organic frameworks (MOFs) to capture and remove volatile radioactive gas from spent nuclear fuel. "This is one of the first attempts to use a MOF for iodine capture," said chemist Tina Nenoff of Sandia's Surface and Interface Sciences Department.

The process also reduces the volume of high-level wastes, a key concern of the Sandia researchers. "The goal is to find a methodology for highly selective separations that result in less waste being interred," Nenoff said.

Part of the challenge of reprocessing is to separate and isolate radioactive components that can't be burned as fuel. The Sandia team focused on removing iodine, whose isotopes have a half-life of 16 million years, from spent fuel.

They studied known materials, including silver-loaded zeolite, a crystalline, porous mineral with regular pore openings, high surface area and high mechanical, thermal and chemical stability. Various zeolite frameworks can trap and remove iodine from a stream of spent nuclear fuel, but need added silver to work well.

"Silver attracts iodine to form silver iodide," Nenoff said. "The zeolite holds the silver in its pores and then reacts with iodine to trap silver iodide."

But silver is expensive and poses environmental problems, so the team set out to engineer materials without silver that would work like zeolites but have higher capacity for the gas molecules. They explored why and how zeolite absorbs iodine, and used the critical components discovered to find the best MOF, named ZIF-8.

"We investigated the structural properties on how they work and translated that into new and improved materials," Nenoff said.

MOFs are crystalline, porous materials in which a metal center is bound to organic molecules by mild self-assembly chemical synthesis. The choice of metal and organic result in a very specific final framework.

The trick was to find a MOF highly selective for iodine. The Sandia researchers took the best elements of the zeolite Mordenite -- its pores, high surface area, stability and chemical absorption -- and identified a MOF that can separate one molecule, in this case iodine, from a stream of molecules. The MOF and pore-trapped iodine gas can then be incorporated into glass waste for long-term storage.

The Sandia team also fabricated MOFs, made of commercially available products, into durable pellets. The as-made MOF is a white powder with a tendency to blow around. The pellets provide a stable form to use without loss of surface area, Nenoff said.

Sandia has applied for a patent on the pellet technology, which could have commercial applications.

The Sandia researchers are part of the Off-Gas Sigma Team, which is led by Oak Ridge National Laboratory and studies waste-form capture of volatile gasses associated with nuclear fuel reprocessing. Other team members -- Pacific Northwest, Argonne and Idaho national laboratories -- are studying other volatile gases such as krypton, tritium and carbon.

The project began six years ago and the Sigma Team was formalized in 2009. It is funded by the U.S. Department of Energy Office of Nuclear Energy.

Sandia's iodine and MOFs research was featured in two recent articles in the Journal of the American Chemical Societyauthored by Nenoff and team members Dorina Sava, Mark Rodriguez, Jeffery Greathouse, Paul Crozier, Terry Garino, David Rademacher, Ben Cipiti, Haiqing Liu, Greg Halder, Peter Chupas, and Karena Chapman. Chupas, Halder and Chapman are from Argonne.

"The most important thing we did was introduce a new class of materials to nuclear waste remediation," said Sava, postdoctoral appointee on the project.

Nenoff said another recent paper in Industrial & Engineering Chemistry Research shows a one-step process that incorporates MOFs with iodine in a low-temperature, glass waste form. "We have a volatile off-gas capture using a MOF and we have a durable waste form," Nenoff said.

Nenoff and her colleagues are continuing their research into new and optimized MOFs for enhanced volatile gas separation and capture.

"We've shown that MOFs have the capacity to capture and, more importantly, retain many times more iodine than current materials technologies," said Argonne's Chapman.

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The above story is reprinted from materials provided by DOE/Sandia National Laboratories, via News wise.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

---

Journal References:

1. Karena W. Chapman, Dorina F. Sava, Gregory J. Halder, Peter J. Chupas, Tina M. Nenoff. Trapping Guests within a Nanoporous Metal–Organic Framework through Pressure-Induced Amorphization. Journal of the American Chemical Society, 2011; 133 (46): 18583 DOI:10.1021/ja2085096
2. Dorina F. Sava, Mark A. Rodriguez, Karena W. Chapman, Peter J. Chupas, Jeffery A. Greathouse, Paul S. Crozier, Tina M. Nenoff. Capture of Volatile Iodine, a Gaseous Fission Product, by Zeolitic Imidazolate Framework-8.Journal of the American Chemical Society, 2011; 133 (32): 12398 DOI: 10.1021/ja204757x

Chemists reveal the force within you: New method for visualizing mechanical forces on cell surface

ScienceDaily (Nov. 9, 2011) — A new method for visualizing mechanical forces on the surface of a cell, reported in Nature Methods, provides the first detailed view of those forces, as they occur in real-time.

"Now we're able to measure something that's never been measured before: The force that one molecule applies to another molecule across the entire surface of a living cell, and as this cell moves and goes about its normal processes," says Khalid Salaita, assistant professor of biomolecular chemistry at Emory University. "And we can visualize these forces in a time-lapsed movie."

Salaita developed the florescent-sensor technique with chemistry graduate students Daniel Stabley and Carol Jurchenko, and undergraduate senior Stephen Marshall.

"Cells are constantly tugging and pushing on their surroundings, and they can even communicate with one another using mechanics," Salaita says. "One way that cells use forces is evident from the characteristic architecture of tissue, like a lung or a heart. If we want to really understand cells and how they work, we have to understand cell mechanics at a molecular level. The first step is to measure the tension applied to specific receptors on the cell surface."

The researchers demonstrated their technique on the epidermal growth factor receptor (EGFR), one of the most studied cellular signaling pathways. They mapped the mechanical strain exerted by EGFR during the early stages of endocytosis, when the protein receptor of a cell takes in a ligand, or binding molecule. The results showed that the cell does not passively absorb the ligand, but physically pulls it inside during the process. Their experiments provide the first direct evidence that force is exerted during endocytosis.

Mapping such forces may help to diagnose and treat diseases related to cellular mechanics. Cancer cells, for instance, move differently from normal cells, and it is unclear whether that difference is a cause or an effect of the disease.

"It's known that if EGFR is over-active, that can lead to cancer," Salaita says. "And one of the ways that EGFR is activated is by binding its ligand and taking it in. So if we can understand how tugging on EGFR force changes the pathway, and whether it plays a role in cancer, it might be possible to design drugs that target this pulling process."

Several methods have been developed in recent years to try to study the mechanics of cellular forces, but they have major limitations.

One genetic engineering approach requires splitting open and modifying proteins of a cell. This invasive technique may change the behavior of the cell, skewing the results.

The technique developed at Emory is non-invasive, does not modify the cell, and can be done with a standard fluorescence microscope. A flexible polymer is chemically modified at both ends. One end gets a fluorescence-based turn-on sensor that will bind to a receptor on the cell surface. The other end is chemically anchored to a microscope slide and a molecule that quenches fluorescence.

"Once a force is applied to the polymer, it stretches out," Salaita explains. "And as it extends, the distance from the quencher increases and the fluorescent signal turns on and grows brighter. We can determine the force being exerted by measuring the amount of fluorescent light emitted."

The forces of any individual protein or molecule on the cell surface can be measured using the technique, at far higher spatial and temporal resolutions than was previously possible.

Many mysteries beyond the biology and chemistry of cells may be explained through measuring cellular forces. How does a cancer cell crawl when a tumor spreads? What are the forces involved in cell division and immune response? What are the mechanics that allow groups of cardiac cells to beat in unison?

"Our method can be applied to nearly any receptor, opening the door to rapidly studying chemical and mechanical interactions across the thousands of membrane-bound receptors on the surface of virtually any cell type," Salaita says. "We hope that measuring cellular forces could then become part of the standard repertoire of biochemical techniques that scientists use to study living systems."

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Journal Reference:

Daniel R Stabley, Carol Jurchenko, Stephen S Marshall, Khalid S Salaita. Visualizing mechanical tension across membrane receptors with a fluorescent sensor. Nature Methods, 2011; DOI: 10.1038/nmeth.1747

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Chemists develop compounds capable of forming heath-resistant, economic and biocompatible gels

ScienceDaily (Nov. 9, 2011) — Eating a yogurt or a jelly, using a pharmaceutical or cosmetic cream or shampoo... are just some of the numerous everyday actions in which we use gels developed through a process of gelation. Researchers from Universitat Jaume I have patented a new family of compounds that enables to develop gels more resistant to high temperatures with a higher level of biocompatibility and able to work with a variety of organic solvents, and all this with an easy synthesis, scalable and low cost.

This family of compounds has significant applications in industries such as pharmaceuticals and cosmetics or food industry, among others.

A jellifying agent is a substance that when is added to a liquid, transforms it into ice. When the liquid used is water, it is called hydrogel. But if the solvents used are organic compounds, they use organojellifying compounds such as the developed by the group Sustainable chemistry: supported reactants and catalysts. Supramolecular chemistry from the UJI, led by the chair professor Santiago Luis. 'Normally, when we develop a compound or family compounds able to form organogels, they only act in such a way in a very small number of solvents. The fundamental difference is that our group of compounds is capable of forming gels with a very high range of solvents', the researcher explains.

Another contribution of the compound is its ability to maintain stability at temperatures up to 100° C, thus allowing the products to keep their properties. In addition, the basic chemical structures that form compounds are amino acids, which provide products that are in most cases biocompatible. 'As they have units easily acceptable by the biological world, they don't have incompatibility, allergies or toxicities problems," Santiago Luis stresses.

To all these advantages, we have to add the fact that these compounds with a jellifying action at low concentrations are cheap.

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Chemists reveal the force within you: New method for visualizing mechanical forces on cell surface

ScienceDaily (Nov. 9, 2011) — A new method for visualizing mechanical forces on the surface of a cell, reported in Nature Methods, provides the first detailed view of those forces, as they occur in real-time.

"Now we're able to measure something that's never been measured before: The force that one molecule applies to another molecule across the entire surface of a living cell, and as this cell moves and goes about its normal processes," says Khalid Salaita, assistant professor of biomolecular chemistry at Emory University. "And we can visualize these forces in a time-lapsed movie."

Salaita developed the florescent-sensor technique with chemistry graduate students Daniel Stabley and Carol Jurchenko, and undergraduate senior Stephen Marshall.

"Cells are constantly tugging and pushing on their surroundings, and they can even communicate with one another using mechanics," Salaita says. "One way that cells use forces is evident from the characteristic architecture of tissue, like a lung or a heart. If we want to really understand cells and how they work, we have to understand cell mechanics at a molecular level. The first step is to measure the tension applied to specific receptors on the cell surface."

The researchers demonstrated their technique on the epidermal growth factor receptor (EGFR), one of the most studied cellular signaling pathways. They mapped the mechanical strain exerted by EGFR during the early stages of endocytosis, when the protein receptor of a cell takes in a ligand, or binding molecule. The results showed that the cell does not passively absorb the ligand, but physically pulls it inside during the process. Their experiments provide the first direct evidence that force is exerted during endocytosis.

Mapping such forces may help to diagnose and treat diseases related to cellular mechanics. Cancer cells, for instance, move differently from normal cells, and it is unclear whether that difference is a cause or an effect of the disease.

"It's known that if EGFR is over-active, that can lead to cancer," Salaita says. "And one of the ways that EGFR is activated is by binding its ligand and taking it in. So if we can understand how tugging on EGFR force changes the pathway, and whether it plays a role in cancer, it might be possible to design drugs that target this pulling process."

Several methods have been developed in recent years to try to study the mechanics of cellular forces, but they have major limitations.

One genetic engineering approach requires splitting open and modifying proteins of a cell. This invasive technique may change the behavior of the cell, skewing the results.

The technique developed at Emory is non-invasive, does not modify the cell, and can be done with a standard fluorescence microscope. A flexible polymer is chemically modified at both ends. One end gets a fluorescence-based turn-on sensor that will bind to a receptor on the cell surface. The other end is chemically anchored to a microscope slide and a molecule that quenches fluorescence.

"Once a force is applied to the polymer, it stretches out," Salaita explains. "And as it extends, the distance from the quencher increases and the fluorescent signal turns on and grows brighter. We can determine the force being exerted by measuring the amount of fluorescent light emitted."

The forces of any individual protein or molecule on the cell surface can be measured using the technique, at far higher spatial and temporal resolutions than was previously possible.

Many mysteries beyond the biology and chemistry of cells may be explained through measuring cellular forces. How does a cancer cell crawl when a tumor spreads? What are the forces involved in cell division and immune response? What are the mechanics that allow groups of cardiac cells to beat in unison?

"Our method can be applied to nearly any receptor, opening the door to rapidly studying chemical and mechanical interactions across the thousands of membrane-bound receptors on the surface of virtually any cell type," Salaita says. "We hope that measuring cellular forces could then become part of the standard repertoire of biochemical techniques that scientists use to study living systems."

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Story Source:

The above story is reprinted from materials provided by Emory University. The original article was written by Carol Clark.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Daniel R Stabley, Carol Jurchenko, Stephen S Marshall, Khalid S Salaita. Visualizing mechanical tension across membrane receptors with a fluorescent sensor. Nature Methods, 2011; DOI: 10.1038/nmeth.1747

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

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Chemists find new dimension to rules for reactions

ScienceDaily (Oct. 20, 2011) — Theoretical chemists at Emory University have solved an important mystery about the rates of chemical reactions and the so-called Polanyi rules.

The findings, published in the journal Science, reveal why a reaction involving methane does not conform to the known rules, a problem that has baffled physical chemists in recent years.

"We showed that a pre-reactive, long-range force can align the reaction of a chorine atom with methane, or natural gas, in a way that actually inhibits the reaction," says Joel Bowman, a professor of theoretical chemistry at Emory and the Cherry L. Emerson Center for Computational Chemistry. "We believe that the theoretical work that we did has extended and modified the Polanyi rules."

Bowman published the results with Gabor Czako, a post-doctoral fellow in theoretical chemistry who performed most of the complex computational and mathematical analyses that uncovered the results.

Long-range, their findings could play a role in the development of cleaner, more efficient fuels.

Understanding the dynamics of chemical reactions is key to driving reactions efficiently, whether in a laboratory experiment or in an industrial application. In 1986, John Polanyi shared the Nobel Prize in chemistry, in part by providing general rules for how different forms of energy affect the rates of reactions.

"The Polanyi rules tell you the best way to deposit energy in a simple molecule to make a chemical reaction occur," Bowman says. "It's a bit like knowing in advance how to invest $1,000 to maximize the return on investment."

Polanyi developed the framework based on studies of simple reactions of chlorine and fluorine atoms with hydrogen gas. As technology has advanced in recent years, some chemists began testing the Polanyi rules for more complicated reactions, and the rules appeared to break down. Most notably, sophisticated molecular beam experiments by Kopin Liu at the Institute of Atomic and Molecular Sciences in Taiwan showed that the reaction of halogen atoms with methane did not conform to the rules.

"Suddenly, the rules appeared to have changed, and no one could explain why," Bowman says. "We decided to roll up our sleeves and attack the problem theoretically."

Bowman and Czako drew from the computational power of the Emerson Center, specialized software and analytical techniques. They first created theoretical-computational simulations of the experiments done by Liu and others, and then described the results mathematically.

"Our calculations showed essentially an exact agreement with the experimental results," Bowman says. "When theory and experiment agree you're happy, but you still want to know why."

Determining why the reactions did not conform to the Polanyi rules was another complicated task, involving quantum mechanics and forces that govern the reaction down to the atomic level.

"As theoreticians, we're able to zoom in and look at the results of our calculations in a way that's virtually impossible in an experiment," Bowman says.

They identified a subtle interplay between the Polanyi rules and a pre-reactive long-range force of methane with chlorine. If you follow the Polanyi rules, this long-range force, or steric control, will misalign the reactants, preventing them from docking correctly and inhibiting a reaction. But if you apportion the energy in the opposite way to the rules, the misalignment is wiped out and the reaction occurs.

"This long-range force was playing a bigger role than was previously realized," Bowman says. "It can actually trump the Polanyi rules, at least in the reactions that Liu and we looked at. The Polanyi rules are certainly not all wrong, they just appear to be too simple to apply to more complex reactions."

The research was funded by the National Science Foundation and the U.S. Department of Energy.

The reactive properties of natural gas are of particular interest since it is an important fuel. Bowman and Czako are now applying their techniques to study the combustion of methane and oxygen, which produces carbon dioxide. "It's important to understand the dynamics of this reaction, because it might lead to more efficient ways to produce fuel, and a reduction in the levels of pollution emitted," Bowman says.

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The above story is reprinted from materials provided by Emory University. The original article was written by Carol Clark.

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Journal Reference:

G. Czako, J. M. Bowman. Dynamics of the Reaction of Methane with Chlorine Atom on an Accurate Potential Energy Surface. Science, 2011; 334 (6054): 343 DOI: 10.1126/science.1208514

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Nature offers key lessons on harvesting solar power, say chemists

ScienceDaily (Sep. 24, 2011) — Clean solutions to human energy demands are essential to our future. While sunlight is the most abundant source of energy at our disposal, we have yet to learn how to capture, transfer and store solar energy efficiently. According to University of Toronto chemistry professor Greg Scholes, the answers can be found in the complex systems at work in nature.

"Solar fuel production often starts with the energy from light being absorbed by an assembly of molecules," said Scholes, the D.J. LeRoy Distinguished Professor at U of T. "The energy is stored fleetingly as vibrating electrons and then transferred to a suitable reactor. It is the same in biological systems. In photosynthesis, for example, antenna complexes composed of chlorophyll capture sunlight and direct the energy to special proteins called reaction centres that help make oxygen and sugars. It is like plugging those proteins into a solar power socket."

In an article in Nature Chemistry to be published Sept. 23, Scholes and colleagues from several other universities examine the latest research in various natural antenna complexes. Using lessons learned from these natural phenomena, they provide a framework for how to design light harvesting systems that will route the flow of energy in sophisticated ways and over long distances, providing a microscopic "energy grid" to regulate solar energy conversion.

A key challenge is that the energy from sunlight is captured by coloured molecules called dyes or pigments, but is stored for only a billionth of a second. This leaves little time to route the energy from pigments to molecular machinery that produces fuel or electricity. How can we harvest sunlight and utilize its energy before it is lost?

"This is why natural photosynthesis is so inspiring," said Scholes. "More than 10 million billion photons of light strike a leaf each second. Of these, almost every red-coloured photon is captured by chlorophyll pigments which feed plant growth." Learning the workings of these natural light-harvesting systems fostered a vision, proposed by Scholes and his co-authors, to design and demonstrate molecular "circuitry" that is 10 times smaller than the thinnest electrical wire in computer processors. These energy circuits could control, regulate, direct and amplify raw solar energy which has been captured by human-made pigments, thus preventing the loss of precious energy before it is utilized.

Last year, Scholes led a team that showed that marine algae, a normally functioning biological system, uses quantum mechanics in order to optimize photosynthesis, a process essential to its survival. These and other insights from the natural world promise to revolutionize our ability to harness the power of the sun.

"Lessons from nature about solar light harvesting" was written by Scholes, Graham Fleming of the University of California, Berkeley, Alexandra Olaya-Castro of University College, London UK and Rienk van Grondelle of VU University in Amsterdam, The Netherlands.

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Journal Reference:

Gregory D. Scholes, Graham R. Fleming, Alexandra Olaya-Castro, Rienk van Grondelle. Lessons from nature about solar light harvesting. Nature Chemistry, 2011; 3 (10): 763 DOI: 10.1038/nchem.1145

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Nature offers key lessons on harvesting solar power, say chemists

ScienceDaily (Sep. 24, 2011) — Clean solutions to human energy demands are essential to our future. While sunlight is the most abundant source of energy at our disposal, we have yet to learn how to capture, transfer and store solar energy efficiently. According to University of Toronto chemistry professor Greg Scholes, the answers can be found in the complex systems at work in nature.

"Solar fuel production often starts with the energy from light being absorbed by an assembly of molecules," said Scholes, the D.J. LeRoy Distinguished Professor at U of T. "The energy is stored fleetingly as vibrating electrons and then transferred to a suitable reactor. It is the same in biological systems. In photosynthesis, for example, antenna complexes composed of chlorophyll capture sunlight and direct the energy to special proteins called reaction centres that help make oxygen and sugars. It is like plugging those proteins into a solar power socket."

In an article in Nature Chemistry to be published Sept. 23, Scholes and colleagues from several other universities examine the latest research in various natural antenna complexes. Using lessons learned from these natural phenomena, they provide a framework for how to design light harvesting systems that will route the flow of energy in sophisticated ways and over long distances, providing a microscopic "energy grid" to regulate solar energy conversion.

A key challenge is that the energy from sunlight is captured by coloured molecules called dyes or pigments, but is stored for only a billionth of a second. This leaves little time to route the energy from pigments to molecular machinery that produces fuel or electricity. How can we harvest sunlight and utilize its energy before it is lost?

"This is why natural photosynthesis is so inspiring," said Scholes. "More than 10 million billion photons of light strike a leaf each second. Of these, almost every red-coloured photon is captured by chlorophyll pigments which feed plant growth." Learning the workings of these natural light-harvesting systems fostered a vision, proposed by Scholes and his co-authors, to design and demonstrate molecular "circuitry" that is 10 times smaller than the thinnest electrical wire in computer processors. These energy circuits could control, regulate, direct and amplify raw solar energy which has been captured by human-made pigments, thus preventing the loss of precious energy before it is utilized.

Last year, Scholes led a team that showed that marine algae, a normally functioning biological system, uses quantum mechanics in order to optimize photosynthesis, a process essential to its survival. These and other insights from the natural world promise to revolutionize our ability to harness the power of the sun.

"Lessons from nature about solar light harvesting" was written by Scholes, Graham Fleming of the University of California, Berkeley, Alexandra Olaya-Castro of University College, London UK and Rienk van Grondelle of VU University in Amsterdam, The Netherlands.

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Journal Reference:

Gregory D. Scholes, Graham R. Fleming, Alexandra Olaya-Castro, Rienk van Grondelle. Lessons from nature about solar light harvesting. Nature Chemistry, 2011; 3 (10): 763 DOI: 10.1038/nchem.1145

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Chemists devise better way to prepare workhorse molecules

ScienceDaily (June 9, 2011) — In chemistry, so-called aromatic molecules compose a large and versatile family of chemical compounds that are the stuff of pharmaceuticals, electronic materials and consumer products ranging from sunscreen to plastic soda bottles.

Writing in the current online issue (June 9) of the journal Science, a team led by University of Wisconsin-Madison chemistry Professor Shannon Stahl reports a new, environmentally friendly way to make substituted aromatic molecules that can be customized for different industrial needs.

As college chemistry students know, aromatic molecules have a special stability conferred by a ring of six carbon atoms with alternating single and double bonds. "The ultimate utility of these molecules depends on the chemical groups attached at the corners of this hexagonal platform," explains Stahl. "Interest in preparing substituted aromatic molecules traces back to the dawn of organic chemistry."

In fact, the 2010 Nobel Prize in Chemistry was awarded for catalytic chemical reactions that allow the introduction of specific groups to the periphery of aromatic molecules. These methods, and older traditional methods, rely on modifying an existing aromatic molecule, Stahl explains. But the stability of aromatic molecules can make such approaches difficult, and existing methods also have many limitations in the types and patterns of chemical groups that can be installed.

The method devised by Stahl and Wisconsin colleagues Yusuke Izawa and Doris Pun owes its success to the discovery of a new palladium catalyst. The catalyst gives chemists a way to peel off hydrogen from cyclic molecules to form aromatic products with the desired substitution patterns already in place. The hydrogen removed by the palladium catalyst is combined with oxygen, and water is formed as the only byproduct.

The Wisconsin team demonstrated the utility and efficiency of the new process on phenols, aromatic compounds that are produced on a large scale as precursors to many kinds of industrial materials and pharmaceutical agents. While the new catalytic method can be used to make a broad spectrum of aromatic molecules of interest to science and industry, the new work will be of most immediate practical use to drug companies, according to Stahl. For example, an anticancer agent that was difficult to make using previously known methods was efficiently produced using the strategy devised by the team.

Stahl notes that the work published June 9 in Science will require more development before it is suitable for large-scale industrial production, but he emphasizes that concepts introduced by the new work will have broad utility. "Many new catalysts, reaction conditions and target molecules can be envisioned. Overall, this route to substituted aromatic molecules has a lot of potential," he says.

The new study was supported by grants from the U.S. National Institutes of Health, the Mitsubishi Chemical Corp. and the U.S. National Science Foundation.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Wisconsin-Madison.

Journal Reference:

Yusuke Izawa, Doris Pun and Shannon S. Stahl. Palladium-Catalyzed Aerobic Dehydrogenation of Substituted Cyclohexanones to Phenols. Science, 9 June 2011 DOI: 10.1126/science.1204183

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Chemists devise better way to prepare workhorse molecules

ScienceDaily (June 9, 2011) — In chemistry, so-called aromatic molecules compose a large and versatile family of chemical compounds that are the stuff of pharmaceuticals, electronic materials and consumer products ranging from sunscreen to plastic soda bottles.

Writing in the current online issue (June 9) of the journal Science, a team led by University of Wisconsin-Madison chemistry Professor Shannon Stahl reports a new, environmentally friendly way to make substituted aromatic molecules that can be customized for different industrial needs.

As college chemistry students know, aromatic molecules have a special stability conferred by a ring of six carbon atoms with alternating single and double bonds. "The ultimate utility of these molecules depends on the chemical groups attached at the corners of this hexagonal platform," explains Stahl. "Interest in preparing substituted aromatic molecules traces back to the dawn of organic chemistry."

In fact, the 2010 Nobel Prize in Chemistry was awarded for catalytic chemical reactions that allow the introduction of specific groups to the periphery of aromatic molecules. These methods, and older traditional methods, rely on modifying an existing aromatic molecule, Stahl explains. But the stability of aromatic molecules can make such approaches difficult, and existing methods also have many limitations in the types and patterns of chemical groups that can be installed.

The method devised by Stahl and Wisconsin colleagues Yusuke Izawa and Doris Pun owes its success to the discovery of a new palladium catalyst. The catalyst gives chemists a way to peel off hydrogen from cyclic molecules to form aromatic products with the desired substitution patterns already in place. The hydrogen removed by the palladium catalyst is combined with oxygen, and water is formed as the only byproduct.

The Wisconsin team demonstrated the utility and efficiency of the new process on phenols, aromatic compounds that are produced on a large scale as precursors to many kinds of industrial materials and pharmaceutical agents. While the new catalytic method can be used to make a broad spectrum of aromatic molecules of interest to science and industry, the new work will be of most immediate practical use to drug companies, according to Stahl. For example, an anticancer agent that was difficult to make using previously known methods was efficiently produced using the strategy devised by the team.

Stahl notes that the work published June 9 in Science will require more development before it is suitable for large-scale industrial production, but he emphasizes that concepts introduced by the new work will have broad utility. "Many new catalysts, reaction conditions and target molecules can be envisioned. Overall, this route to substituted aromatic molecules has a lot of potential," he says.

The new study was supported by grants from the U.S. National Institutes of Health, the Mitsubishi Chemical Corp. and the U.S. National Science Foundation.

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Wisconsin-Madison.

Journal Reference:

Yusuke Izawa, Doris Pun and Shannon S. Stahl. Palladium-Catalyzed Aerobic Dehydrogenation of Substituted Cyclohexanones to Phenols. Science, 9 June 2011 DOI: 10.1126/science.1204183

Note: If no author is given, the source is cited instead.

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