Good news plus lingering concerns for Deepwater Horizon cleanup workers

Several new studies of air and water near the site of the Deepwater Horizon oil spill conclude that cleanup workers may have escaped harm from one of the most worrisome groups of potentially toxic substances in the oil, according to an article in Chemical & Engineering News (CEN), ACS's weekly news magazine. But it cites concerns that another group of potentially harmful chemicals did escape from the water and could create a health hazard for cleanup workers.

The article, by C&EN Senior Editor Elizabeth Wilson, describes research showing that benzene, toluene, ethylbenzene, and xylene — collectively termed BTEX — remained dissolved in the Gulf of Mexico, and did not vaporize into the air where they could be inhaled by cleanup workers. The spill began on July 20, 2010 with an explosion on the Deepwater Horizon facility, 50 miles off the coast of Louisiana, killing 11 oil workers. By the time the well was capped 87 days later, 4.9 million barrels (206 million gallons) of oil had spilled.

Tempering that apparent good news for the health of cleanup workers, however, are concerns that other substance released by the crude oil, substances that do not dissolve as well in water, die become airborne during the 2010 disaster. If so, they could pose a health threat to cleanup workers, the article notes.

More information: "Hyrdocarbons at Gulf Spill Surface" is available at http://pubs.acs.or … 937sci3.html

Provided by American Chemical Society (news : web)

'Synthetic biology' could replace oil for chemical industry

Vats of blue-green algae could one day replace oil wells in producing raw materials for the chemical industry, a UC Davis chemist predicts.

Shota Atsumi, an assistant professor of chemistry, is using "synthetic biology" to create cyanobacteria, or blue-green algae, that convert carbon dioxide in the air into complex hydrocarbons, all powered by sunlight.

Cyanobacteria are single-celled organisms that, like green plants, can use sunlight to turn carbon dioxide and water into sugars and other carbohydrates.

The U.S. Department of Energy has set a goal of obtaining a quarter of industrial chemicals from biological processes by 2025. Today 99 percent of the raw materials used to make paint, plastics, fertilizers, pharmaceuticals and other chemical products come from petroleum or natural gas, according to Atsumi.

While some chemicals, such as biofuels, can be obtained from converted plant material, plants are relatively slow to grow, and using farms to grow fuel takes arable land out of food production.

Instead, Atsumi is engineering cyanobacteria to make chemicals they do not make in nature. By carefully analyzing genes in these and other organisms, his team will assemble artificial synthetic pathways and put them into living cells.

"We can use genes as building blocks to create these new functions," Atsumi said.

Provided by University of California - Davis

Team develops new technique for dating silk

Strand for strand no fabric can compare to the luxurious feel, luminosity and sheen of pure silk. Since millennia, the Chinese have been unraveling the cocoons of the silk worm (Bombyx mori) and weaving the fibers into sumptuous garments, hangings, carpets, tapestries and even artworks of painted silk.

Now, for the first time, scientists at the Smithsonian's Museum Conservation Institute have developed a fast and reliable method to date silk. This new technique, which is based on capillary electrophoresis mass spectrometry, has great potential to improve the authentication and dating of the priceless silk artifacts held in museum and other collections around the world.

The new method uses the natural deterioration of the silk's amino acids--a process known as racemization--to determine its age. As time goes by, the abundance of the L-amino acids used in the creation of the silk protein decreases while the abundance of D-amino acids associated with the silk's deterioration increases. Measuring this ever-changing ratio between the two types of amino acids can reveal the age of a silk sample.

Archaeologists and forensic anthropologists have used this process for decades to date bone, shells and teeth, but the techniques used required sizeable samples, which for precious silk objects are almost impossible to obtain.

"Many things an animal makes are protein based, such as skin and hair. Proteins are made of amino acids," explains Smithsonian research scientist Mehdi Moini, chief author of a recent paper in the journal Analytical Chemistry announcing the new dating method.

"Living creatures build protein by using specific amino acids known commonly as left-handed [L] amino acids. Once an animal dies it can no longer replace the tissues containing left-handed amino acids and the clock starts. As L- changes to D-amino acids [right handed], the protein begins to degrade," Moini explains.

Measuring this ever-changing ratio between left-handed and right-handed (D) amino acids can be used as a scientific clock by which a silk's age can be estimated. In controlled environments such as museum storage, the decomposition process of silk is relatively uniform, rendering D/L measurement more reliable.

The Smithsonian Museum Conservation Institute team used fiber samples taken from a series of well-dated silk artifacts to create a chart of left-hand and right-handed amino-acid calibration ratios against which other silks fabrics can be dated.

Those items included new silk fibers; a silk textile from the Warring States Period, China (475-221 B.C.) from the Metropolitan Museum of Art in New York City; a silk tapestry (1540s) from the Fontainebleau Series, Kunsthistorisches Museum, Vienna, Austria; a silk textile from Istanbul (1551-1599) from the Textile Museum, Washington, D.C.; a man's suit coat (1740) from the Museum of the City of New York; and a silk Mexican War flag (1845-1846) from the Smithsonian's National Museum of American History.

Previously, the scientists write, dating silk has been largely been a speculative endeavor that has mostly relied on the historical knowledge of a silk piece, as well as its physical and chemical characteristics.

The new technique takes about 20 minutes, and requires the destruction of about 100 microgram of silk fiber, making it preferable over C14 (carbon 14) dating, which requires the destruction of so much material that it is prohibitive for most fine silk items.

More information: The article "Dating Silk by Capillary Electrophoresis Mass Spectrometry" appeared in the scientific journal Analytical Chemistry.

Provided by Smithsonian (news : web)

Millions of molecules screened in search for the ideal organic solar cell material

Currently, the cost of electricity from commercial silicon solar cells is about 10 times higher than the cost of utility-scale electricity. In order to make solar cells cost-competitive with currently available energy sources, some researchers are looking to organic materials. Not only are organic materials less expensive than inorganic materials like silicon, but they’re also non-hazardous, lightweight, easily processed, and can be made semi-transparent and molded into almost any shape. The problem is there are literally millions of organic materials to choose from, and identifying those few that have the best optical and electronic properties is extremely challenging.

To address this problem, a team of researchers from Harvard University, the National Autonomous University of Mexico, and Haverford College in Haverford, Pennsylvania, has developed an extremely large-scale automated computational screening method to study potential molecular structures for organic photovoltaic devices (OPVs). They introduced the initiative, called the Harvard Clean Energy Project (CEP), http://cleanenergy.harvard.edu/ in a recent issue of the Journal of Physical Chemistry Letters where they present some early results, with more studies to follow.

CEP’s overall goal is to identify an organic material that can increase the efficiency of OPVs from the current record of 9.2% to 10-15%, as well as expand the currently limited lifetimes to more than 10 years. A solar cell with these two features could push the power generation costs of organic solar cells below that of other currently available energy sources.

To achieve this goal, the project has taken a highly collaborative approach. It relies on input and feedback from experimentalists from Zhenan Bao’s group at Stanford and other research groups. To analyze the large number of molecules, the project combines conventional modeling strategies with strategies from modern drug discovery, along with ideas from machine learning, pattern recognition, and cheminformatics. Also, the project utilizes volunteer computing by IBM’s World Community Grid (WCG) to supply part of the large-scale computational power. Volunteers who would like to donate computer time can download a free and virus-free program from the IBM website that uses their computers for screening the materials while their computer is idle.

“Roughly, every 12 hours of donated free CPU time will result in a new molecule added to our database of candidate organic materials for solar cells,” Alán Aspuru-Guzik of Havard, who is one of the project’s leaders, told PhysOrg.com. “The database will aid scientists in accelerating the discovery of novel solar materials.”

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With traditional approaches to analyzing and characterizing materials, researchers typically rely on their past experiences with certain materials and their own empirical intuition. Due to the long time required for synthesis and characterization, only a few examples can be experimentally studied per year. In contrast, CEP can characterize thousands of molecules per day, and the CEP library already contains about 10 million molecular motifs of potential interest.

“The great variety in properties found in our candidate library is quite remarkable, as is the small parameter space that makes for promising OPVs and that has to be hit,” said Johannes Hachmann of Harvard, another of the project’s leaders. “The latter underlines the value of our high-throughput approach.”

Using a calculation hierarchy, the method rates each candidate motif at each step with respect to the desired properties, and expedites further characterization for the most promising candidates. The hierarchy technique is already proving valuable: a preliminary analysis has revealed that only about 0.3% (3,000–5,000) of the screened structures have the necessary energetic levels to realize organic solar cells with 10% or higher efficiency. While an unaided search would have a very small chance of identifying these molecules, CEP can move all of the promising candidates forward for additional analysis.

“So far, we have made a proof-of-principle study in collaboration with Zhenan Bao’s group at Stanford,” said Aspuru-Guzik. “We screened eight different variants of a parent compound for organic semiconductors, and this resulted in a compound with an astonishing large hole mobility. This gives us confidence that the type of approach followed in the WCG will yield useful information to the community.”

In addition to searching for molecules with specific structures, the project also gives researchers a better understanding of structure-property relationships of molecules in general. Knowing these design principles will allow scientists to not only improve screening, but also to actively engineer novel organic electronics at a future stage.

“On the one hand, the collection provides on-demand access to specific compounds with a wide range of desired properties and electronic structures for all sorts of applications, not only for OPVs,” Hachmann said. “On the other hand it forms a solid foundation to learn about structure-property relationships. Lastly, it will be a useful resource for theoreticians to assess the performance of different computational methods and can serve as a parameter repository in this chemical space.”

As more technical results arrive, the researchers are building a reference database that will be available to the public by 2012. The data should accelerate the search for optimal OPV materials, and provide valuable data for the development of organic electronics in general. The researchers hope that one day the search will lead to a clean source of electricity that can compete with conventional energy sources, although it’s difficult to predict exactly when that will be.

“In principle, we want the search to last as little as possible,” Aspuru-Guzik said. “Obviously, things are more complicated: It takes human time to catalog and understand the results, as well as to select molecules for further screening. We are in the process of selecting the top candidates of our initial screening and releasing them in a publication. We want to further screen the most promising candidates with more calculations to ascertain and verify their potential as organic solar cell materials.”

To participate and download the client software developed by IBM and Harvard, go to http://cleanenergy.harvard.edu and click “Download.” The website contains video tutorials for the installation.

More information: Johannes Hachmann, et al. “The Harvard Clean Energy Project: Large-Scale Computational Screening and Design of Organic Photovoltaics on the World Community Grid.” The Journal of Physical Chemistry Letters, 2011, DOI:10.1021/jz200866s