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Actin Dances the Conga
- Posted at 10:32 AM on Apr. 24, 2010 by ausetute in Chemistry Update Actin molecules form long chains that are part of the matrix that give cells their structure. University of Illinois scientists used fluorescent dye to tag molecules in the chain to see how they move and have discovered that the long chains move like people in a conga line on a crowded dance floor, sometimes the chains are free to move and sometimes they are tightly tangled up with each other. Bo Wang, Juan Guan, Stephen M. Anthony, Sung Chul Bae, Kenneth S. Schweizer, and Steve Granick. Confining Potential when a Biopolymer Filament Reptates. Physical Review Letters, 2010; 104 (11): 118301 DOI: 10.1103/PhysRevLett.104.118301 0 Comments - Post Comment - Permanent Link
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Molecular Paper
- Posted at 12:16 PM on Apr. 16, 2010 by ausetute in Chemistry Update Berkeley Lab scientists have made the largest ever two-dimensional polymer crystal self-assembled in water. The self-assembling sheets are made up of peptoids, engineered polymers that can flex and fold like proteins. Each sheet is just 2 molecules thick, but hundreds of square micrometres in area, just like molecular paper. Individual polymer chains within the peptoid material have been observed using electron microscopy which has confirmed the precise ordering of these chains into sheets. In the future, these nanosheets could be used to control the flow of molecules, or serve as a platform for chemical and biological detection. Ki Tae Nam, Sarah A. Shelby, Philip H. Choi, Amanda B. Marciel, Ritchie Chen, Li Tan, Tammy K. Chu, Ryan A. Mesch, Byoung-Chul Lee, Michael D. Connolly, Christian Kisielowski, Ronald N. Zuckermann. Free-floating ultrathin two-dimensional crystals from sequence-specific peptoid polymers. Nature Materials, 2010; DOI: 10.1038/nmat2742 |
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Graetzel Solar Cells
- Posted at 12:24 PM on Apr. 14, 2010 by ausetute in Chemistry Update The Graetzel Solar Cell is based on the principle of photosynthesis and is composed of a porous layer of nanoparticles of titanium dioxide, TiO2, covered with a molecular dye that absorbs sunlight just like the chlorophyll in green leaves. The dye-coated titanium dioxide is immersed in an electrolyte solution. Two electrodes, titanium dioxide anode and platinum cathode, are placed on either side of conducting solution or electrolyte. Sunlight passes through the cathode and the electrolyte, removing electrons from the titanium dioxide anode which travel through a wire from the anode to the cathode creating an electrical current. Université du Québec à Montréal (2010, April 12). Inexpensive highly efficient solar cells possible. ScienceDaily. Retrieved April 14, 2010, from http://www.sciencedaily.com /releases/2010/04/100406125545.htm |
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Chemistry to Defeat Antibiotic-Resistant Bacteria
- Posted at 7:20 PM on Apr. 12, 2010 by ausetute in Chemistry Update Antibiotic-resistant bacteria such as MRSA can attach to surfaces and then create biofilms, sticky layers of cells that act as a shield and prevent antibiotics from destroying the bacteria underneath. North Carolina State University Chemists have shown that a compound made from a class of molecules known as 2-aminoimidazoles in combination with antibiotics can disperse the biofilms created by certain bacterial strains allowing antibiotics such as penicillin to be more effective, even when the bacteria was penicillin resistant. S. A. Rogers, R. W. Huigens, J. Cavanagh, C. Melander. Synergistic Effects Between Conventional Antibiotics and 2-Aminoimidazole-Derived Antibiofilm Agents.. Antimicrobial Agents and Chemotherapy, 2010; DOI: 10.1128/AAC.01418-09 |
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New Concentration Resources
- Posted at 2:04 PM on Apr. 9, 2010 by ausetute in website update AUS-e-TUTE has just added new tutorials, tests, games, drills and worksheet/quiz wizards for the topic concentration of solutions:
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Element 117
- Posted at 10:14 AM on Apr. 8, 2010 by ausetute in Chemistry Update A team of scientists has succeeded in creating the newest superheavy element, element 117, the only missing element in row seven of the Periodic Table. Element 117 was created by bombardment of berkelium in the Dubna heavy ion accelerator. 6 atoms of element 117 were created. Element 117 was observed to undergo alpha decay to form elements 115 and 113 and so on until the nucleus fissioned, splitting into 2 lighter elements. 26 new elements beyond uranium have been added to the Periodic Table since 1940. DOE/Lawrence Livermore National Laboratory (2010, April 7). Nuclear missing link created at last: Superheavy element 117. ScienceDaily. Retrieved April 8, 2010, from http://www.sciencedaily.com /releases/2010/04/100406181611.htm |
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Killer Beans
- Posted at 12:24 PM on Apr. 6, 2010 by ausetute in Chemistry Update Brazilian scientists report that globulin proteins found in peas, beans and other plant seeds, can ward off insects. Tiny amounts of the coffee bean proteins rapidly killed up to half the cowpea weevil larva used in the study. The protein appears to be harmless to humans so it is thought that in the future the genes for these insect-killing proteins could be inserted into food crops so that the plants produce their own insecticides. Mirela Batista Coelho, Maria Li%u0301gia Rodrigues Macedo, Se%u0301rgio Marangoni, Desiree Soares da Silva, Igor Cesarino, Paulo Mazzafera. Purification of Legumin-Like Proteins from Coffea arabica and Coffea racemosa Seeds and Their Insecticidal Properties toward Cowpea Weevil (Callosobruchus maculatus) (Coleoptera: Bruchidae). Journal of Agricultural and Food Chemistry, 2010; 58 (5): 3050 DOI: 10.1021/jf9037216 |
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Iron Complexes in Mussels
- Posted at 11:33 AM on Mar. 31, 2010 by ausetute in Chemistry Update Mussels use a byssus to tether themselves to surfaces. The byssal threads are covered in a thin, knobby, outer cuticle which is a biological polymer that exhibits epoxy-like hardness while straining up to 100% without cracking. The study of protective coatings, like that employed by mussel's byssal threads, can help scientists design future protective coatings for devices to prolong their lifetimes. Scientists have discovered a high concentration of iron ions in the cuticle on byssal threads as well as the presence of an uncommon modification of the amino acid tyrosine known commonly as Dopa. Dopa is known to have an impressive affinity for complexing with transition metal ions, especially iron. When 2-3 dopa residues complex with an iron ion, they produce a stable complex that can be used to cross-link structural proteins. The cross-links are hard to break, but are reversibly breakable so they can break prior to catastrophic failure. This produces the byssal thread's hard, yet stretchable, coating. Harrington et al. Iron-Clad Fibers: A Metal-Based Biological Strategy for Hard Flexible Coatings. Science, 2010; DOI: 10.1126/science.1181044 |
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Artificial Inorganic Leaves
- Posted at 12:05 PM on Mar. 29, 2010 by ausetute in Chemistry Update While the idea of using hydrogen as a fuel has great appeal because when hydrogen combusts it produces water, the difficulty is producing hydrogen in a cost-effective, sustainable way. Scientists have been modeling nature's own energy harvesters, green leaves. Titanium dioxide was infiltrated into a leaf. Using spectroscopic techniques the scientists confirmed that the structural features in a leaf responsible for light harvesting were replicated in the titanium dioxide structure. The activity of the artificial leaves was then increased by embedding platinum nanoparticles into the leaf's surface. These artificial leaves are up to 30 times more active than the commonly used commercially-available photo-catalysts. American Chemical Society (2010, March 26). Blueprint for 'artificial leaf' mimics Mother Nature. ScienceDaily. Retrieved March 29, 2010, from http://www.sciencedaily.com /releases/2010/03/100325131549.htm |
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GlidArc Reactors : Clean Fuels from Waste
- Posted at 11:55 AM on Mar. 26, 2010 by ausetute in Chemistry Update A GlidArc Reactor uses a gliding arc of electricity to produce a plasma inside the reactor, allowing chemical reactions to occur at much lower temperatures. Custom-designed reactors can clean dirty gases produced by low-tech gasification of local waste, producing a clean mix of carbon monoxide and hydrogen gas to synthesize biofuels. Suitable waste includes corn staver (the leaves and stalks left after harvesting), waste cooking oil, and the glycerol by-product from the production of biodiesel. "The main advantage of such biobased fuels that the GlidArc Technology can create is that they constitute "drop-in replacements" for fossil Diesel oil, gasoline or kerosene, and no modifications are needed in engines, vehicles and distribution systems," Professor Czernichowski from the University of Orleans, France, said. "The biofuels can also be used as additives to various types of engine fuels to improve certain fuel properties. Another important advantage, of course, is their much lower toxicity for mankind and the environment compared to conventional fuels." American Chemical Society (2010, March 25). Process in big-screen plasma TVs can produce ultra-clean fuel. ScienceDaily. Retrieved March 26, 2010, from http://www.sciencedaily.com /releases/2010/03/100322121100.htm |
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A Step Towards Invisibility Cloaks
- Posted at 11:05 AM on Mar. 22, 2010 by ausetute in Chemistry Update University of Michigan scientists have been studying spirals of nano-sized mixed metals that, theoretically, could focus visible light to specks smaller than its wavelength which could lead to the development of Klingon-like invisibility cloaks. Nanoparticles of cadium telluride were dispersed in a water-based solution. After 24 hours under light the nanoparticles had formed flat ribbons, after 72 hours they had twisted and bunched together. Light causes the ribbons to twist by causing a stronger repulsion between the nanoparticles. This newly discovered twisting effect could lead to the development of microelectromechanical systems controlled by light and to nano-scale submarines that could be used for drug-delivery. Sudhanshu Srivastava, Aaron Santos, Kevin Critchley, Ki-Sub Kim, Paul Podsiadlo, Kai Sun, Jaebeom Lee, Chuanlai Xu, G. Daniel Lilly, Sharon C. Glotzer, Nicholas A. Kotov. Light-Controlled Self-Assembly of Semiconductor Nanoparticles into Twisted Ribbons. Science, 2010; 327 (5971): 1355 DOI: 10.1126/science.1177218 |
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Metallic Glass
- Posted at 10:48 AM on Mar. 18, 2010 by ausetute in Chemistry Update Ordinary metallic materials have an ordered, crystalline structure. Metallic glass has a disorganized structure which can improve some properties of the material because boundaries between crystal grains in an ordered structure lead to weaknesses in the structure. Metallic glass is often stronger and more durable than other metals. Metals have a structure in which the atoms are closely packed together. For a long time it has been thought that subjecting metals to higher pressures will not cause them to become more closely packed, reducing their volume and therefore becoming more dense. Cerium-rich metallic glasses such as Ce75Al25, however, do become more dense under pressure. Changes in the electronic structure of the cerium atoms in which 4f electrons bound to specific cerium atoms under low pressure become delocalised under high pressure cause the bond between atoms to shrink, allowing the atoms to pack together more closely. Qiao-shi Zeng, Yang Ding, Wendy L. Mao, Wenge Yang, Stas. V. Sinogeikin, Jinfu Shu, Ho-kwang Mao, and J. Z. Jiang. Origin of Pressure-Induced Polyamorphism in Ce75Al25 Metallic Glass. Physical Review Letters, 2010; 104 (10): 105702 DOI: 10.1103/PhysRevLett.104.105702 |
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Strength of Silk
- Posted at 12:57 PM on Mar. 16, 2010 by ausetute in Chemistry Update Silks are among the toughest materials known. Weight for weight, silks are stronger and less brittle than steel. Massachusetts Institute of Technology Scientists have been studying these remarkable properties of silks. Silks are made up of proteins, some of which are thin, planar sheets called beta-sheets. Hydrogen-bonds connect one beta-sheet to another forming a structure like a stack of pancakes but with the crystal structure within each pancake alternating in their orientation. This allows hydrogen-bonds to work cooperatively, reinforcing adjacent chains against external forces which leads to the outstanding strength of silks. When the crystal size of the beta-sheets is about 3nm the silk is ultra-strong and ductile, but if the crystals are just 2nm larger at 5nm, the silk becomes weak and brittle. This sort of research could lead to the synthesis of new materials that are like silks but using different molecules such as carbon nanotubes. Sinan Keten, Zhiping Xu, Britni Ihle and Markus J. Buehler. Nanoconfinement controls stiffness, strength and mechanical toughness of beta-sheet crystals in silk. Nature Materials, 2010; DOI: 10.1038/nmat2704 |
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AUS-e-NEWS
- Posted at 12:27 PM on Mar. 14, 2010 by ausetute in AUS-e-NEWs The March 2010 issue of AUS-e-NEWS, AUS-e-TUTE's quarterly newslettter, has been emailed out to members and subscribers. Please contact AUS-e-TUTE if you have not received your copy. |
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Silicon and Solar Cells
- Posted at 10:38 AM on Mar. 8, 2010 by ausetute in Chemistry Update A solar cell is composed of two separate layers, one with an abundance of electrons that functions as a negative pole, and one with an abundance of electron holes, or positively-charged spaces, that functions as a positive pole. Energy from the absorption of photons from the sun is used to create electron-hole pairs separated at the interface between the two layers and collected as electricity. Silicon is a popular choice for the semiconductor used in solar cells because of its excellent photo-electric properties, but because solar-cell production to date has required very pure silicon, it has been an energy intensive and expensive choice. Berkeley Lab scientists are developing a new approach to trapping sunlight using thin films of ordered arrays of vertical silicon nanowires that could reduce the costs and improve efficiency. These vertical arrays use radial p-n junctions in which a layer of n-type silicon forms a shell around p-type silicon nanowire core. The photo-excited electrons and holes only move very short distances to the electrodes compared to more traditional planar p-n junctions, so efficiency and light-trapping ability should be enhanced. Erik Garnett and Peidong Yang. Light Trapping in Silicon Nanowire Solar Cells. Nano Letters, 2010; 100202130154041 DOI: 10.1021/nl100161z |
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Organic Molecules Found in the Orion Nebula
- Posted at 9:41 AM on Mar. 5, 2010 by ausetute in Chemistry Update ESA's Herschel Space Observatory has observed numerous organic molecules (carbon-containing compounds) in the Orion Nebula using the Heterodyne Instrument for the Far Infrared (HIFI). The HIFI spectrum recorded a pattern of spikes, each spike representing the emission of light from a specific molecule in the Orion Nebula which is known to be one of the most prolific chemical factories in space. Molecules of water, carbon monoxide, formaldehyde (methanal), methanol (methyl alcohol), dimethyl ether, hydrogen cyanide, and sulfur dioxide have been identified. University of Cologne - Universitaet zu Koeln (2010, March 5). Precursors of life-enabling organic molecules in Orion Nebula unveiled by Herschel Space Observatory. ScienceDaily. Retrieved March 5, 2010, from http://www.sciencedaily.com /releases/2010/03/100304102320.htm |
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Entropy and Water
- Posted at 11:00 AM on Mar. 1, 2010 by ausetute in Chemistry Update Water, H2O, is a very unusual chemical compound. It has the ability to retain large amounts of heat, and to reduce its density instead of increasing its density as it solidifies. Scientists at the Rockefeller University have been investigating the role of water in biology by measuring the interactions between molecules. In the liquid state, each water molecule interacts with its 4 nearest neighbours forming a tetrahedron. The tetrahedrons are not perfect however, and the degree of imperfection changes with changes in temperature and pressure. The more perfect the tetrahedrons are, the more ordered the system is. So scientists can now measure the amount of disorder, or entropy, of a system by measuring the degree of imperfection in the tetrahedrons. These studies could lead to a better understanding of why some substances, like drugs used in chemotherapy, are soluble in water and others are not. It could also lead to a better understanding of protein folding and degradation. Kumar et al. A tetrahedral entropy for water. Proceedings of the National Academy of Sciences, 2009; 106 (52): 22130 DOI: 10.1073/pnas.0911094106 |
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Self-mending Metals
- Posted at 11:03 AM on Feb. 25, 2010 by ausetute in Chemistry Update 'Cold-welding' has been observed at the macro scale when clean, flat pieces of similar metals are bonded together under high pressure or in a vacuum. Now, Rice University Scientists have discovered that gold and silver nano-wires between 3 and 10 billionths of a meter wide can join themselves together without applying heat or pressure. The self-mended wires form a single, strong wire, which, when broken, will not break in the same place as the join. Repeatedly breaking and mending the wires does not affect their electrical properties. Using heat to weld materials at the nano-scale in high density electronic devices can damage the materials' strength or conductivity. Cold-welding could be the solution. Yang Lu, Jian Yu Huang, Chao Wang, Shouheng Sun, Jun Lou. Cold welding of ultrathin gold nanowires. Nature Nanotechnology, 2010; DOI: 10.1038/nnano.2010.4 |
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Nonacene
- Posted at 6:34 AM on Feb. 22, 2010 by ausetute in Chemistry Update Nonacene is a compound with 9 benzene rings joined together in a line and belongs to a class of organic compounds called acenes which are known to be semiconductors and among the best in terms of electrical performance. Unfortunately, acenes are highly unstable, oxidizing rapidly in air. University of New Hampshire Chemists have just made the first stable nonacene derivative. This molecule has the 9 benzene ring backbone of nonacene, but has additional sulfur containing functional groups to provide stability and solubility. Nonacenes could be important to the future development of flexible organic electronic devices and in the production of less expensive solar cells. Kaur et al. Design, Synthesis, and Characterization of a Persistent Nonacene Derivative. Journal of the American Chemical Society, 2010; 132 (4): 1261 DOI: 10.1021/ja9095472 |
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A Biofuel Cell
- Posted at 12:19 PM on Feb. 19, 2010 by ausetute in Chemistry Update French scientists have succeeded in transforming the chemical energy of photosynthesis into electrical energy using a new biofuel cell. During photosynthesis, plants convert carbon dioxide (CO2) and water (H2O) into glucose (C6H12O6) and oxygen (O2), and transform solar energy into chemical energy. The new biofuel cell uses the products of photosynthesis, glucose and oxygen, and is made up of two enzyme-modified electrodes. When the biofuel cell was inserted into a cactus leaf, 9 W/cm2 power was generated. The yield of power is proportional to the intensity of the light, stronger illumination accelerates glucose and oxygen production so more fuel is available for the biofuel cell. |
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