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News Article | May 26, 2017
Site: phys.org

Fertilizers are chemical sources of nutrients that are otherwise lacking in soil. Most commonly, fertilizers supply the element nitrogen, which is essential for all living things, as it is a fundamental building block of DNA, RNA, and proteins. Nitrogen gas is very abundant on Earth, making up 78 percent of our atmosphere. However, most organisms cannot use nitrogen in its gaseous form. To make nitrogen usable, it must be "fixed"—turned into a form that can enter the food chain as a nutrient. There are two primary ways that can happen, one natural and one synthetic. Nitrogen fixation occurs naturally due to the action of microbes that live in nodules on plant roots. These organisms convert nitrogen into ammonia through specialized enzymes called nitrogenases. The ammonia these nitrogen-fixing organisms create fertilizes plants that can then be consumed by animals, including humans. In a 2008 paper appearing in the journal Nature Geoscience, a team of researchers estimated that naturally fixed nitrogen provides food for roughly half of the people living on the planet. The other half of the world's food supply is sustained through artificial nitrogen fixation and the primary method for doing this is the Haber-Bosch process, an industrial-scale reaction developed in Germany over 100 years ago. In the process, hydrogen and nitrogen gases are combined in large reaction vessels, under intense pressure and heat in the presence of a solid-state iron catalyst, to form ammonia. "The gases are pressurized up to many hundreds of atmospheres and heated up to several hundred degrees Celsius," says Caltech's Ben Matson, a graduate student in the lab of Jonas C. Peters, Bren Professor of Chemistry and director of the Resnick Sustainability Institute. " With the iron catalyst used in the industrial process, these extreme conditions are required to produce ammonia at suitable rates." In a recent paper appearing in ACS Central Science, Matson, Peters, and their colleagues describe a new way of fixing nitrogen that's inspired by how microbes do it. Nitrogenases consist of seven iron atoms surrounded by a protein skeleton. The structure of one of these nitrogenase enzymes was first solved by Caltech's Douglas Rees, the Roscoe Gilkey Dickinson Professor of Chemistry. The researchers in Peters' lab have developed something similar to a bacterial nitrogenase, albeit much simpler—a molecular scaffolding that surrounds a single iron atom. The molecular scaffolding was first developed in 2013 and, although the initial design showed promise in fixing nitrogen, it was unstable and inefficient. The researchers have improved its efficiency and stability by tweaking the chemical bath in which the fixation reaction occurs, and by chilling it to approximately the temperature of dry ice (-78 degrees Celsius). Under these conditions, the reaction converts 72 percent of starting material into ammonia, a big improvement over the initial method, which only converted 40 percent of the starting material into ammonia and required more energy input to do so. Matson, Peters, and colleagues say their work holds the potential for two major benefits: Because the technology being developed does not require high temperatures or pressures, there is no need for the large-scale industrial infrastructure required for the Haber-Bosch process. This means it might some day be possible to fix nitrogen in smaller facilities located closer to where crops are grown. "Our work could help to inspire new technologies for fertilizer production," says Trevor del Castillo, a Caltech graduate student and co-author of the paper. "While this type of a technology is unlikely to displace the Haber-Bosch process in the foreseeable future, it could be highly impactful in places that that don't have a very stable energy grid, but have access to abundant renewable energy, such as the developing world. There's definitely room for new technology development here, some sort of 'on demand' solar-, hydroelectric-, or wind-powered process." The nitrogenase enzyme is complicated and finicky, not working if the ambient conditions are not right, which makes it difficult to study. The new catalyst, on the other hand, is relatively simple. The team believes that their catalyst is performing fixation in a conceptually similar way as the enzyme, and that its relative simplicity will make it possible to study fixation reactions in the lab using modern spectroscopic techniques. "One fascinating thing is that we really don't know, on a molecular level, how the nitrogenase enzyme in these bacteria actually turns nitrogen into ammonia. It's a large unanswered question," says graduate student Matthew Chalkley, also a co-author on the paper. Peters says their research into this catalyst has already given them a deeper understanding of what is happening during a nitrogen-fixing reaction. "An advantage of our synthetic iron nitrogenase system is that we can study it in great detail," he says. "Indeed, in addition to significantly improving the efficiency of this new catalyst for nitrogen fixation, we have made great progress in understanding, at the atomic level, the critical bond-breaking and making-steps that lead to ammonia synthesis from nitrogen." If processes of this type can be further refined and their efficiency increased, Peters adds, they may have applications outside of fertilizer production as well. "If this can be achieved, distributed solar-powered ammonia synthesis can become a reality. And not just as a fertilizer source, but also as an alternative, sustainable, and storable chemical fuel," he says. Explore further: Flipping the switch on ammonia production: Process generates electricity instead of consuming energy More information: Matthew J. Chalkley et al. Catalytic N-to-NHConversion by Fe at Lower Driving Force: A Proposed Role for Metallocene-Mediated PCET, ACS Central Science (2017). DOI: 10.1021/acscentsci.7b00014


News Article | May 25, 2017
Site: www.eurekalert.org

Water is the Earth's most abundant natural resource, but it's also something of a mystery due to its unique solvation characteristics -- that is, how things dissolve in it. "It's uniquely adapted to biology, and vice versa," said Poul Petersen, assistant professor of chemistry and chemical biology at Cornell University. "It's super-flexible. It dissipates energy and mediates interactions, and that's becoming more recognized in biological systems." How water relates to and interacts with those systems -- like DNA, the building block of all living things -- is of critical importance, and Petersen's group has used a relatively new form of spectroscopy to observe a previously unknown characteristic of water. "DNA's chiral spine of hydration," published May 24 in the American Chemical Society journal Central Science, reports the first observation of a chiral water superstructure surrounding a biomolecule. In this case, the water structure follows the iconic helical structure of DNA, which itself is chiral, meaning it is not superimposable on its mirror image. Chirality is a key factor in biology, because most biomolecules and pharmaceuticals are chiral. "If you want to understand reactivity and biology, then it's not just water on its own," Petersen said. "You want to understand water around stuff, and how it interacts with the stuff. And particularly with biology, you want to understand how it behaves around biological material -- like protein and DNA." Water plays a major role in DNA's structure and function, and its hydration shell has been the subject of much study. Molecular dynamics simulations have shown a broad range of behaviors of the water structure in DNA's minor groove, the area where the backbones of the helical strand are close together. The group's work employed chiral sum frequency generation spectroscopy (SFG), a technique Petersen detailed in a 2015 paper in the Journal of Physical Chemistry. SFG is a nonlinear optical method in which two photon beams -- one infrared and one visible -- interact with the sample, producing an SFG beam containing the sum of the two beams' frequencies, or energies. In this case, the sample was a strand of DNA linked to a silicon-coated prism. More manipulation of the beams and calculation proved the existence of a chiral water superstructure surrounding DNA. In addition to the novelty of observing a chiral water structure template by a biomolecule, chiral SFG provides a direct way to examine water in biology. "The techniques we have developed provide a new avenue to study DNA hydration, as well as other supramolecular chiral structures," Petersen said. The group admits that their finding's biological relevance is unclear, but Petersen thinks the ability to directly examine water and its behavior within biological systems is important. "Certainly, chemical engineers who are designing biomimetic systems and looking at biology and trying to find applications such as water filtration would care about this," he said. Another application, Petersen said, could be in creating better anti-biofouling materials, which are resistant to the accumulation of microorganisms, algae and the like on wetted surfaces. Collaborators included M. Luke McDermott; Heather Vanselous, a doctoral student in chemistry and chemical biology and a member of the Petersen Group; and Steven Corcelli, professor of chemistry and biochemistry at the University of Notre Dame. This work was supported by grants from the National Science Foundation and the Arnold and Mable Beckman Foundation, and made use of the Cornell Center for Materials Research, an NSF Materials Research Science and Engineering Center.


News Article | May 29, 2017
Site: www.sciencedaily.com

Water is Earth's most abundant natural resource, but it's also something of a mystery due to its unique solvation characteristics -- that is, how things dissolve in it. "It's uniquely adapted to biology, and vice versa," said Poul Petersen, assistant professor of chemistry and chemical biology at Cornell University. "It's super-flexible. It dissipates energy and mediates interactions, and that's becoming more recognized in biological systems." How water relates to and interacts with those systems -- like DNA, the building block of all living things -- is of critical importance, and Petersen's group has used a relatively new form of spectroscopy to observe a previously unknown characteristic of water. "DNA's chiral spine of hydration," published May 24 in the American Chemical Society journal Central Science, reports the first observation of a chiral water superstructure surrounding a biomolecule. In this case, the water structure follows the iconic helical structure of DNA, which itself is chiral, meaning it is not superimposable on its mirror image. Chirality is a key factor in biology, because most biomolecules and pharmaceuticals are chiral. "If you want to understand reactivity and biology, then it's not just water on its own," Petersen said. "You want to understand water around stuff, and how it interacts with the stuff. And particularly with biology, you want to understand how it behaves around biological material -- like protein and DNA." Water plays a major role in DNA's structure and function, and its hydration shell has been the subject of much study. Molecular dynamics simulations have shown a broad range of behaviors of the water structure in DNA's minor groove, the area where the backbones of the helical strand are close together. The group's work employed chiral sum frequency generation spectroscopy (SFG), a technique Petersen detailed in a 2015 paper in the Journal of Physical Chemistry. SFG is a nonlinear optical method in which two photon beams -- one infrared and one visible -- interact with the sample, producing an SFG beam containing the sum of the two beams' frequencies, or energies. In this case, the sample was a strand of DNA linked to a silicon-coated prism. More manipulation of the beams and calculation proved the existence of a chiral water superstructure surrounding DNA. In addition to the novelty of observing a chiral water structure template by a biomolecule, chiral SFG provides a direct way to examine water in biology. "The techniques we have developed provide a new avenue to study DNA hydration, as well as other supramolecular chiral structures," Petersen said. The group admits that their finding's biological relevance is unclear, but Petersen thinks the ability to directly examine water and its behavior within biological systems is important. "Certainly, chemical engineers who are designing biomimetic systems and looking at biology and trying to find applications such as water filtration would care about this," he said. Another application, Petersen said, could be in creating better anti-biofouling materials, which are resistant to the accumulation of microorganisms, algae and the like on wetted surfaces.


News Article | May 26, 2017
Site: www.sciencedaily.com

Melanoma is a particularly difficult cancer to treat once it has metastasized, spreading throughout the body. University of Illinois researchers are using chemistry to find the deadly, elusive malignant cells within a melanoma tumor that hold the potential to spread. Once found, the stemlike metastatic cells can be cultured and screened for their response to a variety of anti-cancer drugs, providing the patient with an individualized treatment plan based on their own cells. "The vast majority of suffering in cancer is caused by metastasis, and these stemlike cells are believed to be the culprit," said Kristopher Kilian, a professor of bioengineering and of materials science and engineering who led the research. "But when you take a patient's cells from a biopsy or excised tumor, they loose their stem cell characteristics once you take them out of the body. We are using chemistry to make designer surfaces to reprogram them to that stemlike state." Kilian's team focused on proteins found in the tumor's environment within the body. They took 12 protein segments that bind to the surface of cancer cells, then mixed and matched them into 78 different combinations in an effort to recreate the body's complex chemical environment. The researchers created arrays of chemical combinations on glass slides and cultured mouse melanoma cells on them to see which combinations triggered the cells to return to their metastatic state. They published their findings in the journal ACS Central Science. "A plastic dish coated with these simple peptide combinations could be used to take a patient's cells, reactivate them to a stemlike state, and screen drugs on them. It's a way to efficiently generate these stemlike metastatic cells to develop patient-specific models for individualized medicine," Kilian said. Screening drugs to specifically target the stemlike cells is important because they may not respond to the same drug that targets the main tumor, Kilian said. The researchers said the array technique for finding stemlike cancer cells could work for many different types of cancer. They currently are working on breast and prostate cancers. "This is where having a high-throughput technique like an array is very powerful," Kilian said. "If you have all the chemical combinations on a single chip, you find out which ones work. If you can isolate the metastatic cancer cells, you can understand them, and then you can treat them."


News Article | May 24, 2017
Site: www.cemag.us

Chemists, materials scientists, and nanoengineers at UC San Diego have created what may be the ultimate natural sunscreen. In a paper published in the American Chemical Society journal ACS Central Science, they report the development of nanoparticles that mimic the behavior of natural melanosomes, melanin-producing cell structures that protect our skin, eyes, and other tissues from the harmful effects of ultraviolet radiation. “Basically, we succeeded in making a synthetic version of the nanoparticles that our skin uses to produce and store melanin and demonstrated in experiments in skin cells that they mimic the behavior of natural melanosomes,” says Nathan Gianneschi, a professor of chemistry and biochemistry, materials science and engineering and nanoengineering at UC San Diego, who headed the team of researchers. “Defects in melanin production in humans can cause diseases such as vitiligo and albinism that lack effective treatments,” Gianneschi adds. Vitiligo develops when the immune system wrongly attempts to clear normal melanocytes from the skin, effectively stopping the production of melanocytes. Albinism is due to genetic defects that lead to either the absence or a chemical defect in tyrosinase, a copper-containing enzyme involved in the production of melanin. Both of these diseases lack effective treatments and result in a significant risk of skin cancer for patients. “The widespread prevalence of these melanin-related diseases and an increasing interest in the performance of various polymeric materials related to melanin prompted us to look for novel synthetic routes for preparing melanin-like materials,” Gianneschi says.


News Article | May 25, 2017
Site: www.sciencedaily.com

Lithium-oxygen systems could someday outperform today's lithium-ion batteries because of their potential for high energy density. However, a number of important issues, such as their poor electrochemical stability must be addressed before these systems can successfully compete with current rechargeable batteries. Now, in ACS Central Science, researchers report a new type of cathode, which could make lithium-oxygen batteries a practical option. Xin-Bo Zhang and colleagues note that most of the problems associated with lithium-oxygen battery systems arise from two highly reduced oxygen species that react readily with the electrolyte and the cathode. Carbon is a common strong-performing cathode, but it is unstable in these systems. So, the team hypothesized that the key to unlocking lithium-oxygen batteries' potential could be to create cathodes that are unreactive to the reduced oxygen species, but that still have the same highly conductive, low-weight, porous characteristics of carbon cathodes. The researchers succeeded in creating an ultralight all-metal cathode. The design incorporated three forms of nickel including a nanoporous nickel interior and a gold-nickel alloy surface directly attached to nickel foam. Compared to carbon cathodes, the system has much higher capacity and is stable for 286 cycles, which is amongst the best for lithium-oxygen systems, and is nearly competitive with current commercial lithium-ion systems. Further experimentation showed that the stability and performance arise from both the metal used and its nanoporous structure, and that both these aspects could be optimized to further improve performance.


News Article | May 26, 2017
Site: www.eurekalert.org

CHAMPAIGN, Ill. -- Melanoma is a particularly difficult cancer to treat once it has metastasized, spreading throughout the body. University of Illinois researchers are using chemistry to find the deadly, elusive malignant cells within a melanoma tumor that hold the potential to spread. Once found, the stemlike metastatic cells can be cultured and screened for their response to a variety of anti-cancer drugs, providing the patient with an individualized treatment plan based on their own cells. "The vast majority of suffering in cancer is caused by metastasis, and these stemlike cells are believed to be the culprit," said Kristopher Kilian, a professor of bioengineering and of materials science and engineering who led the research. "But when you take a patient's cells from a biopsy or excised tumor, they loose their stem cell characteristics once you take them out of the body. We are using chemistry to make designer surfaces to reprogram them to that stemlike state." Kilian's team focused on proteins found in the tumor's environment within the body. They took 12 protein segments that bind to the surface of cancer cells, then mixed and matched them into 78 different combinations in an effort to recreate the body's complex chemical environment. The researchers created arrays of chemical combinations on glass slides and cultured mouse melanoma cells on them to see which combinations triggered the cells to return to their metastatic state. They published their findings in the journal ACS Central Science. "A plastic dish coated with these simple peptide combinations could be used to take a patient's cells, reactivate them to a stemlike state, and screen drugs on them. It's a way to efficiently generate these stemlike metastatic cells to develop patient-specific models for individualized medicine," Kilian said. Screening drugs to specifically target the stemlike cells is important because they may not respond to the same drug that targets the main tumor, Kilian said. The researchers said the array technique for finding stemlike cancer cells could work for many different types of cancer. They currently are working on breast and prostate cancers. "This is where having a high-throughput technique like an array is very powerful," Kilian said. "If you have all the chemical combinations on a single chip, you find out which ones work. If you can isolate the metastatic cancer cells, you can understand them, and then you can treat them." The paper "Combinatorial discovery of defined substrates that promote a stem cell state in malignant melanoma" is available online.


News Article | May 24, 2017
Site: www.cemag.us

Chemists, materials scientists, and nanoengineers at UC San Diego have created what may be the ultimate natural sunscreen. In a paper published in the American Chemical Society journal ACS Central Science, they report the development of nanoparticles that mimic the behavior of natural melanosomes, melanin-producing cell structures that protect our skin, eyes, and other tissues from the harmful effects of ultraviolet radiation. “Basically, we succeeded in making a synthetic version of the nanoparticles that our skin uses to produce and store melanin and demonstrated in experiments in skin cells that they mimic the behavior of natural melanosomes,” says Nathan Gianneschi, a professor of chemistry and biochemistry, materials science and engineering and nanoengineering at UC San Diego, who headed the team of researchers. “Defects in melanin production in humans can cause diseases such as vitiligo and albinism that lack effective treatments,” Gianneschi adds. Vitiligo develops when the immune system wrongly attempts to clear normal melanocytes from the skin, effectively stopping the production of melanocytes. Albinism is due to genetic defects that lead to either the absence or a chemical defect in tyrosinase, a copper-containing enzyme involved in the production of melanin. Both of these diseases lack effective treatments and result in a significant risk of skin cancer for patients. “The widespread prevalence of these melanin-related diseases and an increasing interest in the performance of various polymeric materials related to melanin prompted us to look for novel synthetic routes for preparing melanin-like materials,” Gianneschi says.


News Article | May 24, 2017
Site: www.eurekalert.org

Lithium-oxygen systems could someday outperform today's lithium-ion batteries because of their potential for high energy density. However, a number of important issues, such as their poor electrochemical stability must be addressed before these systems can successfully compete with current rechargeable batteries. Today, in ACS Central Science, researchers report a new type of cathode, which could make lithium-oxygen batteries a practical option. Xin-Bo Zhang and colleagues note that most of the problems associated with lithium-oxygen battery systems arise from two highly reduced oxygen species that react readily with the electrolyte and the cathode. Carbon is a common strong-performing cathode, but it is unstable in these systems. So, the team hypothesized that the key to unlocking lithium-oxygen batteries' potential could be to create cathodes that are unreactive to the reduced oxygen species, but that still have the same highly conductive, low-weight, porous characteristics of carbon cathodes. The researchers succeeded in creating an ultralight all-metal cathode. The design incorporated three forms of nickel including a nanoporous nickel interior and a gold-nickel alloy surface directly attached to nickel foam. Compared to carbon cathodes, the system has much higher capacity and is stable for 286 cycles, which is amongst the best for lithium-oxygen systems, and is nearly competitive with current commercial lithium-ion systems. Further experimentation showed that the stability and performance arise from both the metal used and its nanoporous structure, and that both these aspects could be optimized to further improve performance. The authors acknowledge funding from the Chinese Academy of Sciences, Ministry of Science and Technology of the People's Republic of China, Technology and Industry for National Defense of the People's Republic of China, National Natural Science Foundation of China and Jilin Province Science and Technology Development Program. The paper will be freely available on May 24th, at this link: http://pubs. The American Chemical Society, the world's largest scientific society, is a not-for-profit organization chartered by the U.S. Congress. ACS is a global leader in providing access to chemistry-related information and research through its multiple databases, peer-reviewed journals and scientific conferences. ACS does not conduct research, but publishes and publicizes peer-reviewed scientific studies. Its main offices are in Washington, D.C., and Columbus, Ohio. To automatically receive news releases from the American Chemical Society, contact newsroom@acs.org.


Payments for ecosystem services (PES) have received considerable attention as a promising approach for correcting environmental externalities. Frequent shortcomings or outright lack of performance assessments of environmental interventions in general and PES projects in particular have resulted in recommendations for "optimal" PES designs. Conditionality-paying service providers only if services or proxy inputs are delivered-and targeting-allocating payments based on service gains, provision costs or both-are central to such recommendations. We argue that a) true economic optimality is an unattainable PES objective and improving PES cost-effectiveness is a more realistic aspiration, and that b) current PES programs actually prevent cost-effectiveness analyses because they lack appropriate ecosystem service definitions and thus output measurements. We review the effects of conditionality on service flows and provide a framework for identifying the cost-effective level of conditionality stringency. We identify key analytical methods, data and analysis tools required to improve the cost-effectiveness of PES-or any ecosystem service-projects. Needed analytical concepts, metrics, and monitoring and modeling approaches often are sufficiently available for PES design to begin incorporating them. What is missing is their coherent application. Improving spatial-analytical and monitoring capacities should allow gradual implementation of modifications needed to improve PES cost-effectiveness. © 2012 Elsevier B.V.

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