Monday, March 14, 2011

New molecular robot can be programmed to follow instructions

Scientists have developed a programmable "molecular robot" -- a sub-microscopic molecular machine made of synthetic DNA that moves between track locations separated by 6nm. The robot, a short strand of DNA, follows instructions programmed into a set of fuel molecules determining its destination, for example, to turn left or right at a junction in the track. The report, which represents a step toward futuristic nanomachines and nanofactories, appears in ACS's Nano Letters.

Andrew Turberfield and colleagues point out that other scientists have developed similar DNA-based robots, which move autonomously. Some of these use a biped design and move by alternately attaching and detaching themselves from anchor points along the DNA track, foot over foot, when fuel is added. Scientists would like to program DNA robots to autonomously walk in different directions to move in a programmable pattern, a key to harnessing their potential as cargo-carrying molecular machines.

The scientists describe an advance toward this goal -- a robot that can be programmed to choose among different branches of a molecular track, rather than just move in a straight line. The key to this specialized movement is a so-called "fuel hairpin," a molecule that serves as both a chemical energy source for propelling the robot along the track and as a routing instruction. The instructions tell the robot which point is should move to next, allowing the selection between the left or right branches of a junction in the track, precisely controlling the route of the robot -- which could potentially allow the transport of pharmaceuticals or other materials.

The authors acknowledged funding from the Engineering and Physical Sciences Research Council (EPSRC).

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by American Chemical Society, via EurekAlert!, a service of AAAS.

Journal Reference:

Richard A. Muscat, Jonathan Bath, Andrew J. Turberfield. A Programmable Molecular Robot. Nano Letters, 2011; : 110128131625007 DOI: 10.1021/nl1037165

A sculpture you can't see: the chemistry behind the art

A University of Sydney professor is at the forefront of cutting edge work creating complex and beautiful molecular structures that, until recently, could only be made at a life-sized scale.

"Throughout human history aesthetically pleasing objects have been universally created and admired," said the University of Sydney's Leonard Lindoy, Professor of Chemistry and lead author of a paper featured in the latest issue of the prestigious Nature publication.

"We are just beginning to learn how to mimic this aspect of everyday life, building intricate structures that display artistic nuances at the molecular level, effectively spanning art and science," he said.

The Nature paper outlines Professor Lindoy's team's work creating a sculptural form of three interlinked arms, the shape of which could be described as a cross between an architecturally-designed piece of children's playground equipment and an attachment from a futuristic kitchen mixer.

The structure was formed in the lab over three months, when an iron solution plus other molecular building blocks was left to stand in a flask, resulting in deep red-colored crystals.

Initially the molecule's structure was football-shaped, with each of the arms attached to a point at both ends, with a void in the middle. But Professor Lindoy and colleagues found, "in an apparent demonstration of Aristotle's maxim that 'Nature abhors a vacuum'", that over time the arms became knotted and interlinked.

The resulting shape is known as a 'universal 3-ravel motif'. "The structure exhibits both remarkable intricacy and unusual beauty in its molecular form. There are only three or four previous examples of in this particular kind of exotic formation," Professor Lindoy said.

While still in its infancy, Professor Lindoy said that his team's research into how molecules assemble could ultimately be applied in several areas including industrial processes, energy production and the development of molecular electronics. The work could also contribute to the development of tiny "molecular machines" that, for example, might mimic the role of a natural enzyme.

Provided by University of Sydney

Researcher revolutionizes rubber recycling

Scrap rubber has remained little more than, well, scrap -- until now. University of Akron researcher Dr. Avraam Isayev developed an innovative rubber recovery technology expected to cause a major shift in rubber reprocessing for industrial use.

Isayev, a distinguished professor of polymer engineering, and his student research team invented a unique processing method using a novel technique, ultrasonic devulcanization. Isayev’s patented innovation allows for the recovery of rubber materials, which has been difficult, if not impossible, due to rubber’s vulcanized, or crosslinked, nature. Think scrap-tire heap. Isayev's technology enables devulcanization, or breaking, of the sulfur crosslink bonds in the rubber compound, permitting the once scrap material to be reprocessed and reused.

"Extensive experimental and theoretical studies were conducted based on this and otherrelated inventions,” says Isayev, noting that more than 50 articles and book chapters were published during the last 15 years to develop this technology. The National Science Foundation, NASA and a number of industrial companies funded the studies.

Isayev founded Avraam Corp. to develop an industrial ultrasonic extruder to carry out the process of recovering rubber from tires, roofing materials, shoe soles and other industrially significant products. World leading athletic shoe supplier Nike Inc. funded the research.

Isayev’s cutting-edge research is gaining attention. NorTech, a regional nonprofit technology-based economic development organization and catalyst for growing Northeast Ohio’s emerging technology industries, selected the development as a winner of its 2011 Advanced Materials Innovation Award Feb. 24.

Provided by University of Akron

Mimicking photosynthesis path to solar-derived hydrogen fuel

 Inexpensive hydrogen for automotive or jet fuel may be possible by mimicking photosynthesis, according to a Penn State materials chemist, but a number of problems need to be solved first.

"We are focused on the hardest way to make fuel," said Thomas Mallouk, Evan Pugh Professor of Materials Chemistry and Physics. "We are creating an artificial system that mimics , but it will be practical only when it is as cheap as gasoline or ."

into hydrogen and can be done in a variety of ways, but most are heavily energy intensive. The resultant hydrogen, which can be used to fuel vehicles or converted into a variety of hydrocarbons, inevitably costs more than existing fossil-based fuels.

While some researchers have used to make electricity or use concentrated solar heat to split water, Mallouk's process uses the energy in blue light directly. So far, it is much less efficient than other technologies.

The key to direct conversion is electrons. Like the dyes that naturally occur in plants, inorganic dyes absorb sunlight and the energy kicks out an electron. Left on its own, the electron would recombine creating heat, but if the electrons can be channeled -- molecule to molecule -- far enough away from where they originate, the electrons can reach the catalyst and split the hydrogen from the oxygen in water.

"Currently, we are getting only 2 to 3 percent yield of ," Mallouk told attendees today (Feb. 19) at the annual meeting of the American Association for the Advancement of Science. "For systems like this to be useful, we will need to get closer to 100 percent," he added.

But of electrons is not the only problem with the process. The oxygen-evolving end of the system is a chemical wrecking ball and this means the lifetime of the system is currently limited to a few hours.

"The oxygen side of the cell is making a strong oxidizing agent and the molecules near can be oxidized," said Mallouk. "Natural photosynthesis has the same problem, but it has a self-repair mechanism that periodically replaces the oxygen-evolving complex and the protein molecules around it."

So far, the researchers do not have a fix for the oxidation, so their catalysts and other molecules used in the cell structure eventually degrade, limiting the life of the solar fuel cell.

Currently, the researchers are using only blue light, but would like to use the entire visible spectrum from the sun. They are also using expensive components – a titanium oxide electrode, a platinum dark electrode and iridium oxide catalyst. Substitutions for these are necessary, and other researchers are working on solutions. A Massachusetts Institute of Technology group is investigating cobalt and nickel catalysts, and at Yale University and Princeton University they are investigating manganese.

"Cobalt and nickel don't work as well as iridium, but they aren't bad," said Mallouk. "The cobalt work is spreading to other institutions as well."

While the designed structure of the fuel cell directs many of the to the catalyst, most of them still recombine, giving over their energy to heat rather than chemical bond breaking. The manganese catalysts in photosystem II -- the photosynthesis system by which plants, algae and photosynthetic bacteria evolve oxygen -- are just as slow as ours, said Mallouk. Photosystem II works efficiently by using an electron mediator molecule to make sure there is always an electron available for the dye molecule once it passes its current electron to the next molecule in the chain.

"We could slow down major recombination in the artificial system in the same way," said Mallouk. "Electron transfer from the mediator to the dye would effectively outrun the recombination reaction."

Currently the system uses only one photon at a time, but a two-photon system, while more complicated, would be more effective in using the full spectrum of sunlight.

Mallouk's main goal now is to track all the energy pathways in his cell to understand the kinetics. Once he knows this, he can model the cells and adjust portions to decrease energy loss and increase efficiency.

Provided by Pennsylvania State University (news : web)

Modeling radiation energy deposition in a complex biological system

Research involving selective irradiation of a human skin tissue model is improving how scientists determine the overall effects of low doses of ionizing radiation such as might be received during certain medical procedures or occupational exposures. Scientists at Washington State University-Tri Cities and the Pacific Northwest National Laboratory are modeling electron energy deposition patterns as produced by the electron microbeam developed at PNNL to determine how it may be used in the study of more complex biological systems.

Cells growing as a monolayer in a are frequently used for determining responses to environmental insults such as radiation. However, this model does not include cell-cell and cell-matrix interactions critical to maintaining tissue homeostasis. Using a more realistic and complete tissue model is critical to the development of a mechanistic understanding of the cellular radiation responses that occur in vivo.

In this study, the WSU-TC and PNNL scientists used an artificial skin model made of normal human epidermal and called fibroblasts. The advantage of the model is that it has a well-defined cellular composition that scientists can modify to gain a fundamental understanding of how different cell types interact following irradiation. This understanding will help development of biologically based risk models and help ensure that radiation protection standards are adequate and appropriate.

In a series of recent papers, fluorescent and confocal microscopy images have been used to characterize the detailed cellular morphology of the skin tissue model. Using these images as a guide, Monte Carlo simulations have been performed to establish the energy deposition patterns on the microscopic scale. The determined the feasibility of selectively irradiating only the epidermal layer using the PNNL-developed electron microbeam. Microbeams provide a convenient way to investigate radiation-induced bystander effects. Bystander effects are responses in unirradiated cells that are triggered by signals received from irradiated neighboring cells.

Results of the computer simulation suggest that the skin-tissue model epidermis can be irradiated without significant exposure to the dermal layer. This is because of the energy dependence of the electron microbeam's penetration of the skin sample. The result is a more realistic radiation energy deposition scenario.

Now that the scientists are confident that selective irradiation of the epidermis of skin tissue is feasible using the PNNL electron microbeam, they will begin using this device to understand the role of particular cell types in the radiation-induced response.

More information: Miller JH, et al. 2011. "Simulation of Electron-Beam Irradiation of Skin Tissue Model." Radiation Research 175(1):113-118. doi: 10.1667/RR2339.1
Miller JH, et al. 2011. "Confocal microscopy for modeling electron microbeam irradiation of skin." Radiation and Environmental Biophysics (in press).

Stronger than steel, novel metals are moldable as plastic


Jan Schroers and his team have developed novel metal alloys that can be blow molded into virtually any shape.

( -- Imagine a material that's stronger than steel, but just as versatile as plastic, able to take on a seemingly endless variety of forms. For decades, materials scientists have been trying to come up with just such an ideal substance, one that could be molded into complex shapes with the same ease and low expense as plastic but without sacrificing the strength and durability of metal.

Now a team led by Jan Schroers, a materials scientist at Yale University, has shown that some recently developed bulk metallic glasses (BMGs)-metal alloys that have randomly arranged atoms as opposed to the orderly, found in ordinary metals-can be blow molded like plastics into complex shapes that can't be achieved using regular metal, yet without sacrificing the strength or durability that metal affords. Their findings are described online in the current issue of the journal Materials Today.

"These alloys look like ordinary metal but can be blow molded just as cheaply and as easily as plastic," Schroers said. So far the team has created a number of complex shapes-including seamless metallic bottles, watch cases, miniature resonators and biomedical implants-that can be molded in less than a minute and are twice as strong as typical steel.

The materials cost about the same as high-end steel, Schroers said, but can be processed as cheaply as plastic. The alloys are made up of different metals, including zirconium, nickel, titanium and copper.

The team blow molded the alloys at low temperatures and low pressures, where the bulk softens dramatically and flows as easily as plastic but without crystallizing like regular metal. It's the low temperatures and low pressures that allowed the team to shape the BMGs with unprecedented ease, versatility and precision, Schroers said. In order to carefully control and maintain the ideal temperature for blow molding, the team shaped the BMGs in a vacuum or in fluid.

"The trick is to avoid typically present in other forming techniques," Schroers said. "Blow molding completely eliminates friction, allowing us to create any number of complicated shapes, down to the nanoscale."

Schroers and his team are already using their new processing technique to fabricate miniature resonators for microelectromechanical systems (MEMS)-tiny mechanical devices powered by electricity-as well as gyroscopes and other resonator applications.

In addition, by blow molding the BMGs, the team was able to combine three separate steps in traditional metal processing (shaping, joining and finishing) into one, allowing them to carry out previously cumbersome, time- and energy-intensive processing in less than a minute.

"This could enable a whole new paradigm for shaping metals," Schroers said. "The superior properties of BMGs relative to plastics and typical metals, combined with the ease, economy and precision of blow molding, have the potential to impact society just as much as the development of synthetic and their associated processing methods have in the last century."

Compound useful for studying birth defects may also have anti-tumor properties

In an interesting bit of scientific serendipity, researchers at North Carolina State University have found that a chemical compound useful for studying the origins of intestinal birth defects may also inhibit the growth and spread of cancerous tumors.

During the screening of chemical compounds created by NC State chemist Dr. Alex Deiters, developmental biologist Dr. Nanette Nascone-Yoder found one of particular interest to her research: a compound that induced heterotaxia, a disordering or mirror-image "flipping" of , in the frog embryos she was studying. Nascone-Yoder is particularly interested in the genetic processes involved in proper formation of the gut tube, which later becomes the intestinal tract.

"For the to form properly, it has to develop asymmetrically. This compound disrupts asymmetry, so it could be quite useful in helping us to determine when and where intestinal development goes wrong in embryos," Nascone-Yoder says.

But the compound, dubbed "heterotaxin" by the researchers, had effects beyond just inducing heterotaxia.

"We also noticed that the compound prevents normal blood-vessel formation and prevents from migrating by increasing cellular adhesion – basically, the cells are stuck together and can't move."

Nascone-Yoder and her collaborators searched for known genetic pathways that could regulate all of these different events, and found that the pathway most likely to be affected by heterotaxin was the TGF-beta pathway. TGF-beta is known to play a role in the progression of from normal to metastatic.

"This was exciting, because tumors have to have cells that can migrate and form a blood supply in order for the cancer to spread," Nascone-Yoder adds. "Heterotaxin inhibits those processes, which may make it a good 'lead' candidate for the development of an anti-tumor drug."

Indeed, collaborative experiments with NC State veterinary oncologist Marlene Hauck and cell biologist Philip Sannes showed that heterotaxin quenches the growth of canine tumor cells, and inhibits some of the changes required for human tumor cells to become migratory and invasive – at least in a petri dish. There is still work to do, but heterotaxin and future synthetic analogs could be the harbinger of a new class of cancer-fighting compounds.

The research is published in the Feb. 24 issue of Chemistry & Biology.

More information: "Heterotaxin: a novel TGF-ß signaling inhibitor identified in a multi-phenotype profiling screen in Xenopus embryos", Authors: Nanette Nascone-Yoder, Alex Deiters, et al, North Carolina State University Published: Feb. 24, 2011 in Chemistry & Biology.

Provided by North Carolina State University (news : web)