Sunday, November 27, 2011

Sensible use of biomass: A chemical industry based on renew

In an essay presented in the journal , Esben Taarning and co-workers from the company Haldor Topsoe and the Lindoe Offshore Center (Denmark) describe how a sensible transition from to a chemical industry based on biomass might look.

To date, most of the biomass used by industry has been burned to generate energy. According to the authors, in the long term this is not the optimal use. “It is also not the most sensible solution to convert biomass into fuels,” says Taarning. “In the first place, the amount of biomass available does not meet the demand for fuels; in the second, the chemical characteristics of fuels and biomass are too different, so the processes would be too complex and uneconomical.” Means of transportation should be gradually switched to batteries or fuel cells.” Says Taarning: “In contrast, it really makes sense to use biomass as the for chemical industry. The available biomass should suffice to replace the fossil feedstocks used in the production of chemicals. The chemical characteristics of biomass and many bulk chemicals are also very similar, so the processes should be more economical than those for the conversion into fuels.”

When we do this, however, we need to diverge from the established value chains: instead of using brute force to convert these raw materials into specific platform chemicals that were originally selected because of their easy accessibility when starting from fossil resources, it would be better to use the interesting chemical characteristics already available in the biomass resources themselves and to optimize the use of favorable catalytic reaction pathways. “Through the clever selection of target chemicals it is possible to significantly increase the value added,” says Taarning. Because the development costs will be high and the first processes inefficient, it makes sense to initially concentrate on high-value products, thereby allowing for faster widespread adoption.

Also, many primary products and by-products of our current biofuel industry could be interesting platform chemicals in themselves: for example, ethanol as a starting material for the production of acetic acid, ethylene, and ethylene glycol, or glycerol for conversion into acrylic acid, a polymer precursor.

“The shift from a fossil-based chemical industry to one based on biomass poses many challenges,” says Taarning, “but the possibilities are also great: to develop a more sustainable chemical industry utilizing a more versatile feedstock supply and producing products with superior properties.”

More information: Esben Taarning, Beyond Petrochemicals: The Renewable Chemicals Industry, Angewandte Chemie International Edition 2011, 50, No. 45, 10502–10509, Permalink to the article: … ie.201102117

Provided by Wiley (news : web)

Tear drops may rival blood drops in testing blood sugar in diabetes

Mark Meyerhoff and colleagues explain that about 5 percent of the world's population (and about 26 million people in the U.S. alone) have diabetes. The disease is a fast-growing public health problem because of a sharp global increase in obesity, which makes people susceptible to developing type 2 diabetes. People with diabetes must monitor their blood levels several times a day to make sure they are within a safe range. Current handheld glucose meters require a drop of blood, which patients draw by pricking their fingers with a small pin or lancet. However, some patients regard that pinprick as painful enough to discourage regular testing. That's why Meyerhoff's team is working to develop a new, pain-free device that can use tear glucose levels as an accurate reflection of .

Tests of their approach in laboratory rabbits, used as surrogates for humans in such experiments, showed that levels of glucose in tears track the amounts of glucose in the blood. "Thus, it may be possible to measure tear multiple times per day to monitor blood glucose changes without the potential pain from the repeated invasive blood drawing method," say the researchers.

More information: Measurement of Tear Glucose Levels with Amperometric Glucose Biosensor/Capillary Tube Configuration, Anal. Chem., 2011, 83 (21), pp 8341–8346. DOI: 10.1021/ac201700c

An amperometric needle-type electrochemical glucose sensor intended for tear glucose measurements is described and employed in conjunction with a 0.84 mm i.d. capillary tube to collect microliter volumes of tear fluid. The sensor is based on immobilizing glucose oxidase on a 0.25 mm o.d. platinum/iridium (Pt/Ir) wire and anodically detecting the liberated hydrogen peroxide from the enzymatic reaction. Inner layers of Nafion and an electropolymerized film of 1,3-diaminobenzene/resorcinol greatly enhance the selectivity for glucose over potential interferences in tear fluid, including ascorbic acid and uric acid. Further, the new sensor is optimized to achieve very low detection limits of 1.5 ± 0.4 µM of glucose (S/N = 3) that is required to monitor glucose levels in tear fluid with a glucose sensitivity of 0.032 ± 0.02 nA/µM (n = 6). Only 4–5 µL of tear fluid in the capillary tube is required when the needle sensor is inserted into the capillary. The glucose sensor was employed to measure tear glucose levels in anesthetized rabbits over an 8 h period while also measuring the blood glucose values. A strong correlation between tear and blood glucose levels was found, suggesting that measurement of tear glucose is a potential noninvasive substitute for blood glucose measurements, and the new sensor configuration could aid in conducting further research in this direction.

Provided by American Chemical Society (news : web)

Researchers unravel biochemical factor important in tumor metastasis

According to study corresponding author Shengyu Yang, Ph.D., of Moffitt's Comprehensive Melanoma Research Center and the Department of , elevated Transforming Growth Factor beta in the may be responsible for fascin over-expression, which in turn can promote metastasis in some metastatic tumors.

TGF beta is a versatile cytokine involved in many physiological and pathological processes in adults and in the developing embryo, including cell growth, cell differentiation, cell death (apoptosis) and cellular homeostasis. TGF beta is best known as a tumor suppressor, exerting growth inhibitory roles in normal tissue and early stage tumors. However, many are able to overcome the growth inhibition and secreted elevated levels of TGF beta to promote tumor metastasis. How TGF beta promotes metastasis is not completely understood. The authors suggested that fascin may be the key to understand the pro-metastasis function of TGF beta, as fascin knockdown almost completely abolished TGF beta induced and invasion.

The researchers explained that fascin levels are low or not detected in normal tissues, but are highly elevated in malignant tumors. Also, high fascin expression is associated with poor prognosis. It has been clear for some time, they noted, that there is a causal role for fascin over-expression in tumor cell dissemination. However, the underlying mechanism for the elevation of fascin levels has not been clarified. Their analysis using cell culture- based assay and patient microarray data mining strongly suggests that elevated TGF in tumors lead to fascin overexpression, which in turn promotes metastasis.

"Our data suggests that fascin is an immediate TGF beta target gene essential for its pro-invasion activity in cancer metastasis," explained Yang.

While there have been many studies on the role of fascin in tumor cell migration and metastasis, the current study is first to report that TGF beta elevates fascin protein expression to promote invasion, particularly in tumor cells of spindle-shaped – the kind of morphology associated with high tumor invasiveness and more metastatic disease.

"The finding that TGF beta only induces fascin over-expression in highly metastatic tumor cells is especially interesting," said Yang. "Therapies targeting fascin may block TGF beta mediated metastasis without interfering with the role of TGF beta in normal tissues."

Provided by H. Lee Moffitt Cancer Center & Research Institute

Porous crystals for natural gas storage

A Northwestern University research team has developed a that can save scientists and engineers valuable time in the discovery process. The new algorithm automatically generates and tests hypothetical metal-organic frameworks (MOFs), rapidly zeroing in on the most promising structures. These MOFs then can be synthesized and tested in the lab.

Using their method, the quickly identified more than 300 different MOFs that are predicted to be better than any known material for methane (natural gas) storage. The researchers then synthesized one of the promising materials and found it beat the U.S. Department of Energy (DOE) natural gas storage target by 10 percent.

There already are 13 million vehicles on the road worldwide today that run on natural gas -- including many buses in the U.S. -- and this number is expected to increase sharply due to recent discoveries of natural gas reserves.

In addition to gas storage and vehicles that burn cleaner fuel, MOFs may lead to better drug-delivery, , carbon capture materials and catalysts. MOF candidates for these applications could be analyzed efficiently using the Northwestern method.

"When our understanding of materials synthesis approaches the point where we are able to make almost any material, the question arises: Which materials should we synthesize?" said Randall Q. Snurr, professor of chemical and in the McCormick School of Engineering and Applied Science. Snurr led the research. "This paper presents a powerful method for answering this question for metal-organic frameworks, a new class of highly versatile materials."

The study will be published Nov. 6 by the journal Nature Chemistry. It also will appear as the cover story in the February print issue of the journal.

Christopher E. Wilmer, a graduate student in Snurr's lab and first author of the paper, developed the new algorithm; Omar K. Farha, research associate professor of chemistry in the Weinberg College of Arts and Sciences, and Joseph T. Hupp, professor of chemistry, led the synthesis efforts.

"Currently, researchers choose to create new materials based on their imagining how the atomic structures might look," Wilmer said. "The algorithm greatly accelerates this process by carrying out such 'thought experiments' on supercomputers."

The researchers were able to determine which of the millions of possible MOFs from a given library of 102 chemical building block components were the most promising candidates for natural-gas storage. In just 72 hours, the researchers generated more than 137,000 hypothetical MOF structures. This number is much larger than the total number of MOFs reported to date by all researchers combined (approximately 10,000 MOFs). The Northwestern team then winnowed that number down to the 300 most promising candidates for high-pressure, room-temperature methane storage.

In synthesizing the storage MOF that beat the DOE storage by 10 percent, the research team showed experimentally that the material's actual performance agreed with the predicted properties.

The new algorithm combines the chemical "intuition" that chemists use to imagine novel MOFs with sophisticated molecular simulations to evaluate MOFs for their efficacy in different applications. The algorithm could help remove the bottleneck in the discovery process, the researchers said.

Provided by Northwestern University (news : web)

Researchers moving closer to a soluble solution to Haber-Bocsh process

As all those who have taken very many chemistry courses know, the Haber-Bosch process involves heating a potassium-doped catalyst under high pressure, then mixing it over with hydrogen gas to generate the end product, .

What Holland and his team are trying to do is recreate the same process using a different catalyst. Instead of the regular iron catalysts used in current processes, they would like to use a soluble iron catalyst, which most agree would allow for the process to work under room temperatures. Unfortunately, work by others in trying the same thing has thus far resulted in less than dramatic results, i.e. not enough ammonia was produced.

This new research however looks more promising. What the team has done so far is develop a new iron material that will react with nitrogen gas when exposed to potassium which generates a material that has two nitrides which contain a mixed iron nitride core - which will react with hydrogen gas to create a reasonably large amount of ammonia.

While this doesn’t exactly solve the puzzle of how to get the H-B process to work at room temperature and at normal pressure (because the iron is consumed, thus it’s not truly catalytic) it is a step in the right direction, and the team is optimistic that because of knowledge gained in their experiments, they will be able to build a complex that is truly catalytic, which will then lead to a real solution to the underlying problem.

More information: N2 Reduction and Hydrogenation to Ammonia by a Molecular Iron-Potassium Complex, Science 11 November 2011:
Vol. 334 no. 6057 pp. 780-783. DOI: 10.1126/science.1211906

The most common catalyst in the Haber-Bosch process for the hydrogenation of dinitrogen (N2) to ammonia (NH3) is an iron surface promoted with potassium cations (K+), but soluble iron complexes have neither reduced the N-N bond of N2 to nitride (N3–) nor produced large amounts of NH3 from N2. We report a molecular iron complex that reacts with N2 and a potassium reductant to give a complex with two nitrides, which are bound to iron and potassium cations. The product has a Fe3N2 core, implying that three iron atoms cooperate to break the N-N triple bond through a six-electron reduction. The nitride complex reacts with acid and with H2 to give substantial yields of N2-derived ammonia. These reactions, although not yet catalytic, give structural and spectroscopic insight into N2 cleavage and N-H bond-forming reactions of iron.

? 2011