Saturday, July 9, 2011

Learning from plants: visible light energy harvesting

 

How do they do it? Plants make use of only the energy of sunlight for their requirements. Many researchers are trying to mimic the process to harness the vast energy of the sun. In the article published recently in Angew. Chem. Int. Ed.,[1] Jianzhang Zhao et al. of the Dalian University of Technology (China) showed that long-lived triplet excited states are tremendously important for applications in light harvesting. Now they report in the European Journal of Inorganic Chemistry significantly long room-temperature triplet excited state lifetimes for cyclometallated, coumarin-containing IrIII complexes with strong absorption in the visible range.


Coumarin, which is known for its intense , is a suitable "antenna" to enhance the absorption of complexes to be used as sensitizers. Light-harvesting RuII–coumarin dyads have been designed previously; however, their absorption is in the UV region. The excitation wavelengths of typical cyclometalated IrIII complexes are in the UV or blue region, and their absorption is weak in the . The addition of a coumarin group to the diimine ligand in a cyclometallated iridium(III) complex increased its absorption in the visible region tremendously. Zhao et al. report a light-harvesting cyclometalated IrIII molecular array with intense absorption in the visible region and a triplet excited state with a lifetime over 25 times longer than those of analogous ruthenium compounds.


Although the dyads are weakly phosphorescent (?P = 0.6%), the authors prove that the triplet excited states of the IrIII complexes are efficiently populated upon photoexcitation, by using the complexes as triplet sensitizers for triplet–triplet annihilation upconversion. Upconversion quantum yields (?UC) of up to 23.4% were observed. With these results, the authors also question the classical understanding of triplet–triplet annihilation upconversion, which stipulates that quenching of the phosphorescence of the sensitizer should accompany upconverted fluorescence. Upconversion from a weakly phosphorescent excited state opens the way to a completely new approach to the design of light-harvesting complexes.


[1] S. Ji, W. Wu, W. Wu, H. Guo, J. Zhao, Angew. Chem. Int. Ed. 2011, 50, 1626–1629


More information: Jianzhang Zhao et al, Visible-Light Harvesting with Cyclometalated Iridium(III) Complexes Having Long-Lived 3IL Excited States and Their Application in Triplet–Triplet-Annihilation Based Upconversion, European Journal of Inorganic Chemistry, http://dx.doi.org/ … ic.201100501


Provided by Wiley (news : web)

DSM strengthens yeast technology leadership for 2G biofuels

 Royal DSM announced that it has reached an agreement to acquire C5 Yeast Company B.V. from Royal Cosun. The acquisition will allow DSM to combine C5 Yeast Company’s business with its own advanced yeast and enzyme technologies for second generation biofuels, further increasing its leadership position in this field. Financial details of the acquisition will not be disclosed. Completion of the transaction is subject to customary approvals and notifications.


DSM already has a unique position in the development of second generation biofuels (cellulosic ethanol derived from agricultural residues and non-edible crops), being the only company capable of offering both enzyme and yeast fermentation technologies to increase conversion rates to make the technology commercially viable. The yield of DSM’s advanced yeast technology for second generation bio-fuels on cellulose derived C5/C6 sugars can exceed 90% conversion rate, recent tests have shown.


Microorganisms such as yeast are essential to the biofuel production process as they are needed to convert the fermentable sugars generated by enzymes from biomass into ethanol. There are two primary classes of fermentable sugars that are liberated from cellulosic biomass during hydrolysis, six carbon sugars (C6) and five carbon sugars (C5). Typically yeasts only consume C6 sugars, but DSM’s advanced yeast technology is capable of converting both C6 and C5 sugars to ethanol. DSM wants to be the technology provider for the second generation biorefineries, providing enzymes to convert the biomass into a sugar mix and yeast to convert the C6 sugars as well as the C5 sugars. DSM is convinced this will be a winning combination.


C5 Yeast Company has developed a key yeast technology and extensive patent position with its team of R&D experts. The acquisition of C5 Yeast Company adds additional technology for the conversion of specific fractions of biomass (C5 sugars/arabinose) to DSM’s portfolio, allowing DSM to further optimize its yeast technology.


Rob van Leen, Chief Innovation Officer at DSM said: “This acquisition represents a key strategic step as we further strengthen our existing yeast platform and portfolio of bio-conversion technologies for second generation biofuels and biomaterials. We further increase our leadership position in the field of fermentation technology for mixed sugars derived from agricultural residues and non-edible crops. With our bright science and strong technology position we are bringing second generation biofuels closer to mass-scale production, reducing society’s dependence on fossil feed stocks and avoiding the food versus fuel dilemma.”

Renaissance of 200-year old technology could ease 21st century sustainability challenges

The obscure technology used in heated automobile seats, gadgets that charge iPhones from the heat of a campfire, and other devices is undergoing a renaissance and could well emerge as a new "green" substitute for traditional sources of energy and play other key roles in addressing some of society's most pressing sustainability issues. That's the conclusion of an article on the technology — termed thermoelectrics — in the current issue of Chemical & Engineering News (C&EN) the American Chemical Society's weekly newsmagazine.

In the article, C&EN Senior Editor Mitch Jacoby points out that the key scientific discoveries underpinning thermoelectrics date to the early 1800s. The effect involves direct conversion of temperature differences to electric current and the use of electric current to either absorb or release heat, thereby cooling or heating objects. Thermoelectric is at the heart of climate-conditioned car seats, that recharge personal electronics from campfires, and could be used in refrigerators with no moving parts, and an array of other applications.

Manufacturers in the 1960s were actively producing thermoelectric cooling and power-supply devices. Although that niche market, mainly for the military and aerospace industries remained, interest in the thermoelectric effect dwindled. But during recent years, there has been resurgence in interest from both manufacturers and scientists. Advances in materials used to make thermoelectric devices are paving the way for multiple new applications, described in the article.

More information: “Thermoelectrics Make a Comeback” at http://pubs.acs.or … 925sci1.html

Provided by American Chemical Society (news : web)

Wacker Commissions Silicone Rubber Compounding Plant in India

 The Munich-based chemical group Wacker has commissioned a compounding plant at its joint venture site Wacker Metroark Chemicals Pvt. Ltd. near Kolkata, India, for the manufacture of ready-to-use silicone elastomers. The plant is designed for an annual production volume of several thousand metric tons and can be expanded in stages as demand requires. It is intended to supply India’s strongly growing economy with high-quality silicone compounds faster and more flexibly. Several million euros are planned for investment in this plant.


“India is one of our fastest-growing sales markets,” says Dr. Bernd Pachaly, head of Wacker’s Engineering Silicones business unit. “The new SILMIX® facility is constructed according to Wacker standards and will produce silicone compounds for the Indian electronics, automotive and medium and high-voltage insulator market as well as for other industries.” During the start-up event in Kolkata, Pachaly’s deputy Dr. Johann Schuster pointed out that Wacker is one of the leading manufacturers of silicone elastomers for electric insulators. “By manufacturing such products locally, we can serve the market much more flexibly and significantly reduce lead times while still delivering the expected high product quality.” The SILMIX® plant has been designed so that production capacity can be adjusted to meet current market requirements in a short period of time. Schuster: “If necessary, we can respond very quickly to additional demand.”


Soumitra Mukherjee, Managing Director of Wacker Metroark Chemicals (WMC), praised the investment as an important milestone for the joint venture. “Wacker and Metroark have been working together with great success for over a decade. With our range of high quality silicone products, we are already market leaders in many industries in India today.” Mukherjee pointed out that the plant includes a state-of-the-art lab for quality control. With its new compounding plant in Kolkata, WACKER is excellently positioned. “This way it is possible to test and develop high quality silicone compounds for the Indian market in India itself,” emphasized Mukherjee. “This is a major competitive advantage for our customers, who are often under great pressure to deliver quality on time.”


For the manufacture of silicone compounds, the crosslinker, pigment and other additives are usually mixed into the rubber base. Blends such as these are used in a number of industries, including the automotive sector, the electrical industry and the heavy current industry.


 

Breaking the chain: 'Molecular cap' blocks processes that lead to Alzheimer's, HIV

 A new advance by UCLA biochemists has brought scientists one step closer to developing treatments that could delay the onset of Alzheimer's disease and prevent the sexual transmission of HIV.


The researchers report that they have designed molecular inhibitors that target specific proteins associated with Alzheimer's disease and to prevent them from forming amyloid fibers, the elongated chains of interlocking proteins that play a key role in more than two dozen degenerative and often fatal diseases.


"By studying the structures of two key proteins that form amyloids, we were able to identify the small chain of responsible for amyloid fiber formation and engineer a 'molecular cap' that attaches to the end of the fibers to inhibit their growth," said research leader David Eisenberg, director of the UCLA–Department of Energy Institute of Genomics and Proteomics and a Howard Hughes Medical Institute investigator.


The study was published online June 15 in the journal Nature and will be available in an upcoming print edition.


"This research is an important first step toward the development of structure-based drugs designed against amyloid diseases," said Eisenberg, who is a UCLA professor of chemistry, biochemistry and biological chemistry and a member of the California NanoSystems Institute at UCLA. "Our results have opened up an avenue so that universities and industry can start creating therapeutics that could not have been produced 10 years ago."


Toward delaying Alzheimer's disease
Amyloid fibers are elongated, water-tight structures formed from two linked sheets. Proteins from each sheet contribute side chains, causing them to interlock like the teeth of a zipper, Eisenberg said.


The fibers are found not only Alzheimer's disease but in a variety of conditions, including Lou Gehrig's disease, Parkinson's disease, type II diabetes and a family of disorders related to mad cow disease, among others. In Alzheimer's and other neurodegenerative diseases, the tau protein forms amyloid fibers inside brain cells, destroying them through a mechanism that is still being investigated.


Though many serious diseases are characterized by amyloid fibers, Alzheimer's is the most prevalent, Eisenberg said. Today there are 5 million patients in the U.S. who suffer from Alzheimer's, with 500,000 new cases every year. Alzheimer's health care cost this year alone have been estimated at $178 billion, including the value of unpaid care for Alzheimer's patients provided by nearly 10 million family members and friends.


"By the year 2050, it is projected that there will be 19 million Alzheimer's patients," Eisenberg said. "The care of so many patients with this debilitating illness could be a substantial fraction of the gross domestic product of the United States."


Eisenberg and his research team found that of the entire tau protein, a small chain of just six amino acids — abbreviated VQIVYK — was responsible for the formation of amyloid fibers. By studying the structure of the fibers using microcrystallography, a method developed at UCLA for this research, the team was able to use the fibers as a template to design an inhibitor that could 'cap' the fiber and stop it from growing.


The results were dramatic. The introduction of the inhibitor into a tau protein solution completely prevented amyloid fiber formation, validating the idea that the structure-based design of therapeutics for amyloid diseases is a plausible option.


Despite this success, there is still a long road ahead before a viable therapeutic can be developed to combat the onset of Alzheimer's in human patients, Eisenberg said. The inhibitor, a chain of amino acids, is far too large to penetrate deep into the brain where the tau proteins form amyloid fibers.


"This research is an important step toward identifying smaller molecules that can be utilized to develop a therapeutic," Eisenberg said. "Our goal is to be able to delay the onset of Alzheimer's disease."


Preventing the transmission of HIV
Unlike the tau protein, the SEVI (semen-derived enhancer of viral infection) protein is a far more accessible target for a molecular blocker because it builds amyloid fibers in a vaginal environment, a key process in the sexual transmission of HIV, Eisenberg said.


"The presence of SEVI makes the rate of HIV infection through up to 100,000 times more likely," he said. "By blocking SEVI, we have a method for inhibiting the sexual ."


Though the tau and SEVI proteins have different structures and unrelated functions, they both form amyloid fibers with similar morphology, making it possible to design two separate inhibitors using the same process, according to Eisenberg.


The SEVI blocker proved to be equally effective in preventing fiber growth, bolstering the idea that blockers can be designed for other diseases associated with amyloid fibers as well.


"Though many tests remain, it seems we could be on the way to developing a therapeutic," Eisenberg said. "Our hope is that we could make a blocker that could be applied with a vaginal gel or spray that would help to prevent HIV infection."


The tau and SEVI protein inhibitors were designed using synthetic amino acids, similar to the standard protein building blocks of the human body. But these synthetic amino acids were flipped, as if viewed in a mirror, or had added side chains not normally found in nature. Enzymes in the human body that are programmed to break apart protein-like chains are, in principle, unable to recognize the non-natural amino acids, keeping the blockers safe to latch on to the target proteins.


This research was federally funded by the National Institutes of Health, the National Science Foundation and the U.S. Department of Energy, as well as by the Howard Hughes Medical Institute and the Joint Center for Translational Medicine.


Other co-authors of this study included UCLA postdoctoral scholars Stuart Sievers and Lin Jiang; UCLA graduate students Howard Chang and Anni Zhao; John Karanicolas, an assistant professor at the University of Kansas; Jason Stevens, an undergraduate at the University of Kansas; David Baker, a professor at the University of Washington; and professor Jan M√ľnch and researcher Onofrio Zirafi, of the University of Ulm in Germany.


Small molecules, big job
A second research team also led by Eisenberg recently announced that it had identified four small molecules that bind to amyloid fibers, including a promising candidate called 'orange-G' that wedges into the zipper-like fiber and may be able to break it apart.


This study was published June 14 in PLoS Biology, an online journal of the Public Library of Science.


"These are the first small molecules visualized as they bind to amyloid-like fibers," Eisenberg said. "These small molecules are less likely to be broken up in the body and can potentially be modified to force apart amyloid fibers or serve as diagnostic tools to identify infected areas of the body."


Eisenberg and his research team found that orange-G was uniquely able to pierce the impenetrable "steric zippers" that seal the water-tight amyloid fibers of the amyloid-beta protein that is responsible for forming senile plaques in Alzheimer's disease.


"In 10 years we have gotten to the point where we are starting to understand the structural biology of amyloid fibers and how to inhibit them and how to interfere with them," Eisenberg said. "The next step is to make practical molecules that inhibit and break amyloid fibers — that is the ultimate goal."


Co-authors on this UCLA research included Kym Faull, professor of psychiatry and biobehavioral sciences; Jorge Barrio, professor of molecular and medical pharmacology; researchers Michael Sawaya and Jie Liu; postdoctoral scholars Meytal Landau, Lin Jiang and Stuart Sievers; and graduate student Arthur Laganowsky.


Provided by University of California Los Angeles (news : web)

Effective CO2 Capture on a Large Scale

A pilot project by Siemens and E.ON has shown that emissions of the greenhouse gas carbon dioxide from power plants can be effectively captured on a large scale. At the Staudinger coal-fired power plant near Hanau, Germany, more than 90 percent of the carbon dioxide (CO2) in the facility’s flue gas was separated. Another result of the large-scale project, which has been running since 2009, is that the flue gas scrubbing process doesn’t reduce the plant’s efficiency to the extent that had been expected. Based on this finding, the Siemens process is also suitable for use in larger demonstration facilities.


Separation of CO2 from power plant exhaust gases is one of the ways in which plants that run on fossil fuels can help protect the climate. The CO2 is removed from the flue gas by means of Siemens’ post-combustion process. The carbon dioxide is captured with a special scrubbing agent consisting of an amino acid salt solution. These acids occur in nature and aren’t harmful to the environment. The aqueous amino acid salt solution is almost completely non-volatile, so it generates practically no solvent emissions. Unlike previous processes, the new method doesn’t require extensive cleaning of the flue gas after the carbon dioxide is captured. What’s more, the scrubbing agent removes other pollutants in the flue gas besides CO2 and can be repeatedly reused.


In addition to being very environmentally friendly, the process — which is called PostCap — is also energy efficient. Thanks to improvements to the process made by the experts at Siemens Energy, the power plant’s efficiency is only reduced by about six percentage points. That’s far less than was expected: Previous estimates had indicated a loss of about ten percentage points.


 

Probing the secrets of the ryegrasses

Loline alkaloids protect plants from attack by insects and have other interesting features that have yet to be studied in detail. Chemists from Ludwig-Maximilians-Universitaet in Munich, Germany, have developed a method for the effective synthesis of these compounds, which will facilitate further investigations in biology and medicine.

Chemists from Ludwig-Maximilians-Universitaet in Munich led by Professor Dirk Trauner have developed a concise and efficient method for the synthesis of the alkaloid loline and related compounds. Loline alkaloids are a biologically interesting group of natural products, which have unusual physicochemical and pharmacological characteristics, but are as of yet poorly understood. They are produced by fungal symbionts that infect weeds and , and act as deterrents of insects and other herbivores. Some of the agents synthesized by endophytic fungi are toxic to , producing a syndrome known as the staggers.

Indeed, such toxic weeds (commonly called ryegrass or cockle) were much feared in antiquity and are mentioned both by Virgil and in the New Testament. Lolines however are comparatively innocuous to mammalian herbivores, and might therefore be of some therapeutic use. The loline alkaloid temuline has attracted particular attention in another context because it can strongly bind carbon dioxide. Lolines are relatively small molecules and have a fairly simple structure, but of the compounds has proven to be quite challenging.

"Our synthetic route is highly efficient and, with a maximum of 10 steps, very short," says Dirk Trauner, who led the project. "It will allow us to make these compounds in sufficient quantities to enable their various aspects to be investigated in detail. We should then be able to dissect the of interactions of the plants and their fungal parasites with insects and bacteria. We now plan to use our synthetic material to identify the receptor for loline ."

Provided by Ludwig-Maximilians-Universitat Munchen

Danfoss appoints president for Danfoss India

Noel Ryan has been appointed President of Danfoss India, taking up the role on September 1st. He will be based in Chennai, India.


India is a very important market for the Danfoss Group and the Danfoss India President function has been established to support the Group’s growth and continued expansion in the country.


Noel Ryan comes from a job as Senior Vice President Sales & Marketing, responsible for refrigeration sales globally and he will continue in this role alongside his new position as President of Danfoss India. Before that he was heading the global sales in Danfoss Industrial Automation, and prior to that he was based in China heading up the Asia Pacific Region. He holds a degree in chemical engineering and an MBA and has been with Danfoss since 1997.


Danfoss opened its first office in India in 1998 and has since then grown to include 350 employees of which 150 work for Sauer-Danfoss. Going forward, Danfoss has ambitious goals in India and aims to continue this expansion through increased sales, manufacturing and product development, as well as by keeping its customers in focus every step on the way.