It heals and grows together: Polymer with amazing self-healing properties

It heals and grows together: Polymer with amazing self-healing properties

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(PhysOrg.com) -- Sooner or later, a cut to the skin or a broken bone will heal on its own; however, a scratch to a car's paint or a tear in the wing of an airplane will not. Materials with self-healing properties could help extend the durability of products and make repairs easier.

Krzysztof Matyjaszewski and his co-workers at Carnegie Mellon University (Pittsburgh, USA) and Kyushu University (Japan) have now developed a polymer that can repair itself when irradiated with UV light -- over and over again. As the scientists report in the journal Angewandte Chemie, this is the first material in which capped covalent bonds repeatedly reattach, even allowing fully separated pieces to be fused back together.

Some previous solid self-healing materials contain tiny capsules that tear open to release a chemical agent when the material is damaged and have been able to repair themselves only one time. Other materials, including some gels, can repair themselves repeatedly but lack the covalent bonds that increase materials strength and stability.

In contrast, the new polymeric material produced by the American and Japanese team is stable and repairs itself again and again. The secret to their success is that the polymer is cross-linked through trithiocarbonate units. These are carbon atoms bonded to three sulfur atoms, two of which use their second bonding position to attach to another carbon atom. These groups have a special property: they can restructure under UV light. The light breaks one carbon–sulfur bond in the trithiocarbonate groups. This produces two radicals -- molecules with a free, unpaired electron. The radicals are very reactive and attack other trithiocarbonate groups to form new carbon–sulfur bonds while breaking others to form more free radicals. The chain reaction stops when two radicals react with each other.

The researchers were able to heal cut polymer fragments with irradiation—either immersed in liquid or in bulk. They only had to firmly press the cut edges together and irradiate them. The edges grew back together by means of the radical re-organization process described above.

The self-healing effect goes much further: even shredded polymer samples could simply be pressed together and irradiated to be fused into a continuous piece. The resulting object was in the shape of the cylindrical tube in which the procedure was carried out. This self-healing process can be carried out repeatedly on the same sample. The material is thus also interesting as a new recyclable product.

CSIRO grants global license for new polymer technology

CSIRO grants global license for new polymer technology

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CSIRO has signed a global licensing agreement for its patented RAFT technology. Reversible Addition-Fragmentation chain Transfer (or RAFT) technology is an elegant and powerful polymerisation process that has given rise to a new branch of polymer chemistry.

RAFT enables the development of very complex molecules that can be used for a wide range of products. The technology is already generating major improvements in the areas of coatings and paints, electroactive materials, fuel additives, biomaterials, polymer synthesis, personal care, drug delivery agents and car components.

About 3200 papers have been published on RAFT developments, coupled with over 200 patents granted to research and commercial institutions globally.

Monomer Polymer, a US company which specialises in manufacturing specialty monomers and sophisticated polymers has agreed to market the technology worldwide.

Monomer-Polymer and Dajac Labs CEO Stephen Bell said having access to RAFT technology will allow the company to ?undertake controlled radical polymerizations and consequently, create additional success and opportunity in material development?.

Additionally, Monomer-Polymer said that the licensing agreement would enable the company to strengthen their position as a key player in the synthesis, development and scale-up of specialty monomers and resulting polymer systems. A unique aspect of Monomer-Polymer?s chemistries is the internal expertise with organosilanes which should open up unique uses of RAFT to create polymers with organosilicon functionalities in the architecture.

?This new technology is creating global impact and has been licensed by a wide range of Australian and multinational companies,? CSIRO?s Business Development Manager for RAFT Kate Dawson said.

Monomer-Polymer and Dajac Labs is a manufacturer of specialty monomers and polymers used for coatings, adhesives, medical devices, dental resins, water treatment, academic and industrial R&D.

New surface may kill antibiotic-resistant staph bacteria with fluorescent light

New surface may kill antibiotic-resistant staph bacteria with fluorescent light

The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) infections is well known, causing an estimated 19,000 deaths and $3-4 billion in healthcare costs per year in the U.S. What is less well known is that this increased infection and resistance rate has not been met with a simultaneous development of novel antimicrobial and antibiotic agents; in fact, only three classes of antibiotics have been developed since the 1950s.

To address this need, scientists at the University of New Mexico are working on a new type of antimicrobial surface that is inhospitable to MRSA but won't harm people or animals. Their results will be presented today at the AVS 57th International Symposium & Exhibition, which takes place this week at the Albuquerque Convention Center in New Mexico.

The new polymer-type material, "conjugated polyelectrolyte" (CPE) with an arylene-ethynylene repeat-unit structure, has been effective at killing Gram-negative bacteria, enabling its use in a wide range of potential applications. For instance, certain "light-activated" CPEs are inert toward bacteria in the absence of light, and display bacteria-killing activity with the addition of light. This opens up many potential applications, including the possibility of using these polymers as antibacterial countertops that may be sterilized using regular fluorescent lights.

Until recently, it was unknown if the CPEs would exhibit similar biocidal activity toward mammalian cells. In-vitro testing performed on these CPEs at the University of New Mexico is an important first step in determining whether they are harmful to humans at concentrations envisioned in potential applications. In a poster presented today at the AVS Conference, Kristin Wilde will present the results.

Tiny particles can deliver antioxidant enzyme to injured heart cells

Tiny particles can deliver antioxidant enzyme to injured heart cells

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Fluorescent green polyketal particles stay in the heart three days after injection. Credit: Michael Davis

Researchers at Emory University and the Georgia Institute of Technology have developed microscopic polymer beads that can deliver an antioxidant enzyme made naturally by the body into the heart.

Injecting the enzyme-containing particles into rats' hearts after a simulated heart attack reduced the number of dying cells and resulted in improved heart function days later.

Michael Davis, PhD, is presenting the results Sunday evening at the American Heart Association Scientific Sessions in Orlando. Davis is assistant professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.

The enzyme in the particles, called superoxide dismutase (SOD), soaks up toxic free radicals produced when cells are deprived of blood during a heart attack. Previously scientists have tried injecting SOD by itself into injured animals, but it doesn't seem to last long enough in the body to have any beneficial effects.

"Our goal is to have a therapy to blunt the permanent damage of a heart attack and reduce the probability of heart failure later in life," Davis says. "This is a way to get extra amounts of a beneficial antioxidant protein to the cells that need it."

The simulated heart attacks caused a 20 percent decrease in the ability of the rats' hearts to pump blood that was completely prevented by the particles, he says.

The particles are made of a material called polyketals, developed by Niren Murthy, PhD, assistant professor of biomedical engineering at Georgia Tech and Emory. The polyketals encase the enzyme and are taken up by cells within the heart. There the particles slowly release the enzyme.

The microparticles break down into nontoxic components in the body -- an advantage over other biodegradable polymers like PLGA (polylactic-co-glycolic acid), already approved for use in sutures and grafts. When polymers such as PLGA are made into particles for drug delivery, they can induce inflammation.

Davis and his colleagues have also used the polyketal microparticles to encase anti-inflammatory drugs. This is the first report on the antioxidant enzyme-containing particles' use in a model of heart attack.

Emory and Georgia Tech scientists have also used SOD-containing particles to treat mice engineered to have a deficiency in SOD in the lung.

Although the SOD particles had a protective effect when the heart was examined three days after the simulated heart attack, the beneficial effects weren't as strong three weeks later. The rats' hearts still had a 35 percent improvement compared to untreated animals, Davis says. Combining them with microparticles containing the anti-inflammatory drugs proved to provide an additional boost.

"This is likely because it is important to scavenge free radicals at early time points, but inflammation becomes more important later on," he says.

More information: http://www.nature. … mat2299.html

Source: Emory University (news : web)

On the Death of Polymers: Revisiting Termination Rate Coefficients in Radical Homopolymerization

On the Death of Polymers: Revisiting Termination Rate Coefficients in Radical Homopolymerization

(PhysOrg.com) -- Although radical polymerization is used in the synthesis of about half the world's polymers, details of exactly what is going on in the reaction soup in complex industrial settings have been sketchy at best. As the materials enter our lives as, for example, drugs, coatings, fibers and solar cells, controlling their reactions and therefore their properties is extremely important.

Scientists in New Zealand have recently addressed a fundamental part of this story by considering termination rate coefficients for a couple of very common reactions, using results from new analytical techniques to revisit our old understanding. They found the way the small polymers (oligomers) in the system move and their speed, i.e., their diffusion behavior, to be the critical factor. This work is published in a special issue of Macromolecular Chemistry and Physics, devoted to radical polymerization.

The people responsible, Greg Russell and his colleagues at the University of Canterbury, are experts in polymer kinetics. Russell explains, ?The majority of chemists simply try to bring about reactions by mixing different chemicals together under different conditions. However it is also important, especially for those who make chemical products on a large scale, to have precise quantitative descriptions of the speeds at which reactions occur. Chemical kinetics is the field of work that develops such descriptions. It is therefore an area where chemistry and mathematics intersect.?

He goes on to say, ?Arguably the hardest nut to crack in the radical polymerization scheme has been the termination reaction. In layman's terms, termination is the fundamental reaction whereby a polymer molecule stops growing larger. A reasonable analogy is human death, the process which ceases human life and thus prevents a human's age from mounting and mounting. In radical polymerization this reaction is diffusion controlled in rate, which means that its speed is determined by how fast the molecules move.? This speed of movement can depend on many factors such as how long the molecule is, the number of obstacles around the polymer, the temperature of the system, and so on. ?This is the origin of the complexity of the termination reaction, and is the reason why, after over 60 years of intensive study, it is still not fully understood, not nearly.?

In this work Russell revisited some of the earliest questions about termination. ?Recent years have seen the development of highly specialized techniques for measuring termination rate coefficients under precisely controlled conditions. I have taken this information and attempted to see whether it is consistent with systems where many different termination reactions occur at once, as is the case in commercial processes. For the monomer styrene I find there is consistency, but for methyl methacrylate there is not.?

In trying to explain this result, he eliminated most of the conventional views, and came to the conclusion that the answer lies with the oligomers in each system, which seem to have slightly different diffusional behavior.

Philipp Vana works at the University of Göttingen, where Greg Russell is currently on sabbatical. He specializes in radical polymerization and serves on the Advisory Board of Macromolecular Chemistry and Physics. He is the Guest Editor of the special issue. In his view, ?Russell?s paper is especially exciting, as it demonstrates that the information gathered by modern and advanced methods is useful to reevaluate the results obtained by older methods. Completely new insights can be extracted by such an approach.? He adds that Russell?s work not only adds new information to the field, but also presents a nice view of the complete picture, ?which helps us to understand the complete history of science instead of getting a short snapshot of the present.?

This historical perspective of the field is especially pertinent as the special issue focused on the kinetics and mechanism of radical polymerization was prepared in order to honor Michael Buback, who turns 65 this year and who, according to the editor Vana, ?undisputably is one of the doyens in this field.? Recent years have seen the invention of new controlled polymerization methods and Vana says it is of ?vital importance to fundamentally understand these new techniques in order to exploit their full potential for material design. The newly invented polymerization technologies also provided new avenues for unlocking the secrets of the conventional processes. Many important questions could be answered recently and it seems to be justified to resumé at this stage and to identify, which major questions need further attention.?

Radical predictions in polymer chemistry

Radical predictions in polymer chemistry

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Credit: iStockphoto.com/Martin McCarthy

Free radicals may have a bad reputation for causing ozone depletion and premature aging, but they are in fact extremely useful for making novel materials, particularly polymers. Skilled chemists can link up a wide range of free radicals into long-chain polymers using a technique called atom transfer radical polymerization (ATRP). Using different metal catalysts, one can precisely control the rates of polymerization and termination and therefore the architecture and functionality of the polymer.

Fabio di Lena and Christina Chai at the A*STAR Institute of Chemical and Engineering Sciences have now performed the first-ever theoretical modeling of copper-catalyzed ATRP to explain quantitatively how radical polymerization rates are influenced by molecular structures and properties—laying out a critical roadmap for the production of next-generation polymer materials.

The success of an ATRP reaction depends on how well the metal catalyst generates and deactivates organic radicals by intermittently stealing or giving up electrons. If radical production is too fast, the polymerization stops, while sluggish activation or deactivation makes it hard to produce high-quality polymers. Unfortunately, fine-tuning ATRP rates is tricky because researchers must simultaneously optimize many diverse factors such as catalyst and radical geometries, solvents and reaction conditions.

To solve this problem, di Lena and Chai turned to computer-aided molecular design, a technique widely employed in the pharmaceutical drug discovery. They first performed theoretical calculations to extract hundreds of numerical parameters or ‘molecular descriptors’ corresponding to specific structural and chemical properties for a series of ATRP copper catalysts and organic radicals. They then conducted sophisticated statistical analyses on the data to reveal subsets of principal descriptors that had the most influence over polymerization rates.

Next, the team combined their chemical intuition with stringent testing to further narrow the list of descriptors. Finally, biology-inspired artificial intelligence techniques called genetic function algorithms were used to produce mathematical models that relate ATRP rates to algebraic combinations of descriptors like energy levels, molecular volumes and bond lengths. According to di Lena, these models are striking because they agree with the generally accepted mechanistic picture of ATRP and can provide unprecedented predictive insights.

“This method should facilitate the design of new ATRP catalysts by screening, in a virtual way, hundreds of metal complexes at time,” says di Lena. “Labs will only need to prepare the most promising candidates, saving time and money.” Di Lena is also confident that the method will become a powerful tool for developing polymers with tailored properties and functions.

Stretched molecule ends up shorter than it started (w/ Video)

Stretched molecule ends up shorter than it started (w/ Video)

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A ring-like polymer called gDFC was stretched (middle) and sprung back to shape smaller than it began

(PhysOrg.com) -- Crazy bands are cool because no matter how long they've been stretched around a kid's wrist, they always return to their original shape, be it a lion or a kangaroo.

Now a Duke and Stanford chemistry team has found a polymer molecule that's so springy it snaps back from stretching much smaller than it was before.

Duke graduate student Jeremy Lenhardt and associate professor Stephen Craig have been systematically hunting through a library of polymers in search of a molecule that might be useful for "self-healing" materials. They hope to find a polymer that can trigger a chemical reaction when it is stretched and enable a material to build its own repairs.

Imagine a sheet of Saran Wrap that could fix a microscopic puncture before the hole ever got big enough to see. This would require that the polymer molecules immediately around the tear could somehow jump into action and perform new chemistry to build bridges across the hole.

To stretch polymers and see what happens to them, Lenhardt uses an apparatus that pumps up and down on a solution filled with polymers, pressurizing it and depressurizing it 20,000 times a second which causes tiny bubbles to form fleetingly. The void created by the bubbles exerts a tug on the ends of some of the polymers in the solution and stretches them, if only for a billionth of a second.

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After being stretched by ultrasonication, a ring-shaped gem-difluorocyclopropane (gDFC) forms a transition state 1,3-diradical, and then snaps back to shape smaller than it began. Duke graduate student Jeremy Lenhardt narrates.

"Think of two rafts going down a river with a rope between them," Craig explained. "As the first raft enters a rapids and accelerates forward, that rope - the polymer - gets pulled taught and stretches."

Over and over Lenhardt ran the experiment, characterizing different polymer species that became more reactive when stretched, potentially able to do "stress-induced chemistry."

Then, while looking at polymers that contained tiny ring-shaped molecules called gem-difluorocyclopropanes (gDFC), he was surprised to find that some of these molecules emerged from the stretching noticeably shorter than when they went in.

"I ran up to his office," Lenhardt said. " 'Steve, something funny is going on here. Look at this!' " A technique called nuclear magnetic resonance had revealed the shapes of the rings after pulling and shown that they were, in fact, shorter.

But not only were the gDFCs snapping back smaller than they started, it also appeared that before snapping back they were actually trapped in an unusual stretched state far longer than normal, a reactive state called a 1,3-diradical.

Normally, as a molecule goes through a reaction, it passes through a special point known as a transition state, and stays there for only ten to a hundred femtoseconds, "a tenth of a millionth of a millionth of a second," Craig said. This makes it extraordinary hard to actually watch chemistry happen, so chemists usually can only infer what happens at the transition state by what they've seen before and after.

Work by their Stanford collaborators showed that the trapped 1,3-diradicals are in fact one type of these usually fast-moving transition states, but in Lenhardt's experiments they were essentially stopped in their tracks and trapped for nanoseconds, tens of thousands of times longer than usual.

This might be a window for watching transition states in action, Craig said. "We can trap these things long enough to probe new facets of their reactivity."

Lenhardt has begun doing just that, stretching the polymers to learn more about these transition states and seeing if he can watch other molecules by using this technique as a sort of stop-action camera.

"Every chemical reaction has a high energy state that you have to guess at," Lenhardt said. "But maybe, in some cases, you don't have to guess anymore."

The team's findings appear Aug. 27 in Science.

Simulations aim to unlock nature's process of biomineralization

Simulations aim to unlock nature's process of biomineralization

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These are models of the peptides -- one neutral (a) and one charged (b) -- used in simulations of biomineralization processes being conducted at the Ohio Supercomputer Center by the University of Akron?s Dr. Hendrik Heinz. Credit: Hendrik Heinz, UA

A University of Akron researcher is leveraging advanced modeling and simulation techniques to more precisely understand how organic materials bond to inorganic materials, a natural phenomenon that if harnessed, could lead to the design of composite materials and devices for such applications as bone replacement, sensing systems, efficient energy generation and treatment of diseases.

Hendrik Heinz, Ph.D., an assistant professor of polymer engineering at UA, is accessing the systems of the Ohio Supercomputer Center (OSC) to study the process of biomineralization, nature's ability to form complex structures, such as bones, teeth and mollusk shells, from peptides.

"Research in our group aims at the understanding of complex interfacial phenomena, particularly biomineralization and organic photovoltaics, at the molecular scale using computer simulation," said Heinz.

"Simulation with atomistic and coarse-grain models and the development of computational tools goes hand in hand with collaborative experimental efforts."

"Advanced materials remains one of the cornerstones of research supported by the Ohio Supercomputer Center and is fundamental to both the economic legacy and future prospects for the State of Ohio," noted Ashok Krishnamurthy. "OSC is committed to providing state-of-the-art computational and storage resources to scientists, such as Dr. Heinz, who are focused on the design of fascinating new classes and applications of materials."

In a recent paper published by Interface, a journal of The Royal Society, Heinz describes how induced charges modify the interaction of proteins, peptides and bond-enhancing surfactants with metal surfaces. In another recent article, published in the Journal of the American Chemical Society, Heinz explains how he used molecular dynamics simulations to investigate molecular interactions involved in the selective binding of several short peptides to the surfaces of gold, palladium and a palladium-gold bimetal.

"Advances in materials science such as in biomedical and energy conversion devices increasingly rely on computational techniques and modeling," Heinz said. "In particular, interfaces at the nanoscale are difficult to characterize experimentally, such as charge transport mechanisms in solar cells, the formation of biominerals, and self-assembly of polymers in multi-component materials. Model building and simulation are critical to understand dynamic processes across the length and time scales."

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This is an illustration of a neutrally charged peptide and water positioned near the first layer of gold atoms (mirror image in pink) in a simulation conducted at the Ohio Supercomputer Center by The University of Akron?s Dr. Hendrik Heinz. Credit: Hendrik Heinz, UA

This summer, Heinz received $430,000 for two years of research funding from the National Science Foundation's prestigious CAREER award program. Heinz and his research team are taking an interdisciplinary approach using concepts from physics, chemistry, biology, polymer science and engineering, as well as computation and statistical mechanics. The grant supports the development of new computational tools to understand biotic-abiotic interactions at the molecular level, as well a team of student researchers, ranging from graduates and undergraduates to high school pupils.

"We have carried out quantitative molecular simulations of inorganic-organic interfaces in excellent agreement with experimental results and developed accurate molecular models for inorganic components," Heinz explained. "These concepts serve as a starting point for understanding biomineralization processes and the performance of hybrid photovoltaic cells, as current examples. Our research efforts aim at complementing experimental results by molecular-level models to intelligently design (bio)molecules, interfaces, and, ultimately, devices."

From molecule to object: Largest synthetic structure with molecular precision

From molecule to object: Largest synthetic structure with molecular precision

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(PhysOrg.com) -- Organic chemists have always been trying to imitate biology. Although it is possible to make many molecules that imitate biomolecules in terms of structure and function, it remains a challenge to attain the size and form of large biomolecules. An international team led by A. Dieter Schluter at the ETH Zurich (Switzerland) has now introduced a branched polymer that resembles the tobacco mosaic virus in size and cylindrical form. As the researchers outline in the journal Angewandte Chemie, this is the largest synthetic macromolecule with defined shape and atomic structure reported to date.

Previously, the largest reported synthetic structures with a defined atomic structure were polystyrene polymers with a molecular mass of about 40 million Daltons. However, this value corresponds to a small fraction of the mass of large DNA molecules. Formation of a large synthetic molecule that also has a defined form is much more difficult. For biologists, however, it is routine. Even the simplest organism has a well-defined form, such as the rod-shaped tobacco mosaic virus. For chemists it is a model: a massive molecular ensemble with perfect control over its chemical structure, function, size, and molecular form.

Schlüter and co-workers have now presented a branched polymer that approximates the size and form of the tobacco mosaic virus. Their complex synthesis, which requires 170,000 bond-forming reactions in a single molecule, led to a structurally defined, linear macromolecule with a diameter of about 10 nm and a molecular weight of 200 million Daltons. It thus has a molar mass, cross section, and cylindrical form comparable to the tobacco mosaic virus.

The new macromolecule is a dendronized polymer: it consists of a linear backbone with highly and regularly branched side chains. “This is the biggest synthetic macromolecule with a defined chemical structure and defined form to date,” according to Schlüter. “Our experiment is a first step toward the synthesis of molecular objects.” A structure is considered to be an object if it keeps its form regardless of its environment, when its interior can be distinguished from the outer environment, and when there is a clear boundary between the two. There are many synthetic nano-objects, however these are not single molecules, but are aggregates of several or many individual molecules.

Striding towards a new dawn for electronics

Striding towards a new dawn for electronics

Conductive polymers are plastic materials with high electrical conductivity that promise to revolutionize a wide range of products including TV displays, solar cells, and biomedical sensors. A team of McGill University researchers have now reported how to visualize and study the process of energy transport along one single conductive polymer molecule at a time, a key step towards bringing these exciting new applications to market.

"We may easily study energy transport in a cable as thick as a hair, but imagine studying this process in a single polymer molecule, whose thickness is one-millionth of that!" said Dr. Gonzalo Cosa of McGill's Department of Chemistry, lead researcher.

Working in collaboration with Dr. Isabelle Rouiller of McGill's Department of Anatomy and Cell Biology, the team used state-of-the-art optical and electron microscopes and were able to entrap the polymer molecules into vesicles - tiny sacs smaller than a human body cell. The researchers visualized their ability to transport energy in various conformations.

"This research is novel because we are able to look at energy transport in individual polymer molecules rather than obtaining measurements arising from a collection of billions of them. It's like looking at the characteristics of a single person rather than having to rely on census data for the entire world population," Cosa explains. Conductive polymers are long organic molecules typically referred to as nanowires. Components along the polymer backbone successfully pass energy between each other when the polymer is collapsed (coiled within itself), but the process is slowed down when the polymer backbone is extended. A greater understanding of how this process works will enable us to develop a range of technologies in the future."

The studies are critical to applications in daily life such as sensors involving the detection and the differentiation of cells, pathogens, and toxins. They may also help in the future to develop hybrid organic-inorganic light harvesting materials for solar cells.

The research was published online in the Proceedings of the National Academy of Sciences.

Moving polymers through pores

Moving polymers through pores

This shows the typical configurations of polymer translocation through nanopores. Credit: None

The movement of long chain polymers through nanopores is a key part of many biological processes, including the transport of RNA, DNA, and proteins. New research reported in The Journal of Chemical Physics, which is published by the American Institute of Physics, describes an improved theoretical model for this type of motion.

The new model addresses both cylindrical pores and tapering pores that simulate the a-hemolysin membrane channel. "Current models do not take into account the motion of the polymer inside the pore," says author Anatoly Kolomeisky of Rice University. "The leading monomer can move back and forth many times before it finally crosses the line to the other side of the membrane. Not accounting for this behavior introduces errors into predictions."

By improving the boundary conditions for polymer movement inside the pore, researchers demonstrated a significant increase in total time in the pore compared to earlier models. In modeling a tapering pore, they confirmed that translocation occurs faster when the polymer enters the wide side of the pore.

Possible technological applications include advances in DNA sequencing and the development of biosensors using membranes. "To design an effective sensor, it is essential to understand what you are observing and how the molecule reaches the detector," says Kolomeisky.

Genetic inspiration could show the way to revolutionise information technology

Genetic inspiration could show the way to revolutionise information technology

(PhysOrg.com) -- Chemists at the University of Reading have created a synthetic form of DNA that could transform how digital information is processed and stored.

Just as the information in a book is made up of a linear sequence of letters, so the information needed for all living things to function and reproduce is embodied in a linear sequence of chemical units. These make up the chains of DNA and RNA, where an enormous amount of information (the 'genome') is stored in a very small space to direct the molecular processes of life.

A new paper, which appears in Nature Chemistry on June 27, shows for the first time that many of the features of biological information processing can be reproduced in synthetic polymer chains.

The Reading team, led by Howard Colquhoun, Professor of Materials Chemistry in the Department of Chemistry, has designed and synthesised short sequences of a synthetic information-bearing polymer.

In the long term, researchers believe this could revolutionise the future of digital information. Synthetic polymer systems could allow information densities several million times higher than current systems.

Crucial to the work is the creation of tweezer-shaped molecules that pick out information along a chain. The two arms of the tweezer 'feel' the different sequences available and then clamp on to the chain at the precise sequence where the chain structure and tweezer structure are most complementary.

Several tweezer molecules can bind next to one another on the polymer chain, allowing them to 'read' and translate extended, long-range polymer-sequence information. Most notable is that different types of tweezer molecules start reading at different positions on the chain. This selectivity means different types of information can be read from the same sequence which increases the amount of information available.

Professor Colquhoun said: "This type of process is paralleled in the processing of genetic information. In the future, we plan to develop methods for writing new information into the polymer chains with the long-term aim of developing wholly synthetic information technology, working at the molecular level."

Mass production of polymer solar cells within reach

Mass production of polymer solar cells within reach

Ten years of intensive research and development at Risoe DTU (Technical University of Denmark) is now materialized in a fully operational production line for polymer solar cells at the Danish company Mekoprint A/S. Polymer solar cells which is an inexpensive alternative to silicon solar cells, has a significant industrial potential.

Production of polymer solar cells starts from a roll of flexible foil onto which the solar cell is built layer by layer by printing and finally rolled up onto the coil again. Encapsulated and ready-to-use units can thereafter be cut from the roll and according to the customer's specification. As the whole process from feedstock to finished product is performed roll-to-roll, the new production line paves the way towards mass production of solar cells and thereby correspondingly low prices.

Risoe DTU has supplied the printing technology as a complete package consisting of a custom-made printing head, inks for printing the solar cell's various layers and training of operators. Mekoprint has contributed with an established industrial infrastructure and their core technology which is industrial roll-to-roll production.

Professor at Risoe DTU Frederik C. Krebs is the driving force behind the Danish polymer solar cells. Ten years ago he started out with a bright idea, his two hands and a strong dedication. Today Frederik Krebs is the head of an international leading research team counting more than 25 persons - a team capable of combining world-class science with a strong desire to bring science out into real life. The Risø team distinguishing themselves by being first to demonstrate new and innovation applications for the polymer solar cell: "The Solar Hat" - a hat powering a small FM radio (Roskilde Festival 2008), a solar-powered reading lamp for African schoolchildren (Zambia 2009) and the world's first grid-connected PV installation based on the polymer technology (Risoe 2009).

Risø's and Mekoprint's staffs have over the last months worked hard to rebuild one of Mekoprint's existing printing line to the new production, and the very first solar cells from this line were produced at 22 June 2010.

A line producing polymer solar cell is an important incentive for continuing the activities at Risoe DTU. The polymer solar cell technology is still young and immature compared to the 50-year old silicon technology. The gap between the two technologies is to be gradually reduced by focused research and development, and this task is already addressed by the Risø team.

Mekoprint's production strengthens Denmark's position among the international front runners in industrialization of polymer solar cells. "Mekoprint has the competencies and the experience necessary to manufacture high-volume and high-quality products for the electronics industry. The ability to conduct quality assurance of processes is essential when taking new products from the lab to the market, and this is where Mekoprint adds decisive value to the research project," says Karsten Ries, Divisional Director and responsible for the project at Mekoprint A/S.

UCI researchers develop world's first plastic antibodies

UCI researchers develop world's first plastic antibodies

?Plastic antibodies? that UCI scientists used to stop the spread of bee venom in mice could be designed to combat deadlier toxins and pathogens. Photo by Hoang Xuan Pham

UC Irvine researchers have developed the first "plastic antibodies" successfully employed in live organisms - stopping the spread of bee venom through the bloodstream of mice.

Tiny polymeric particles - just 1/50,000th the width of a human hair - were designed to match and encase melittin, a peptide in bee venom that causes cells to rupture, releasing their contents. Large quantities of melittin can lead to organ failure and death.

The polymer nanoparticles were prepared by "molecular imprinting" a technique similar to plaster casting: UCI chemistry professor Kenneth Shea and project scientist Yu Hoshino linked melittin with small molecules called monomers, solidifying the two into a network of long polymer chains. After the plastic hardened, they removed the melittin, leaving nanoparticles with minuscule melittin-shaped holes.

When injected into mice given high doses of melittin, these precisely imprinted nanoparticles enveloped the matching melittin molecules, "capturing" them before they could disperse and wreak havoc - greatly reducing deaths among the rodents.

"Never before have synthetic antibodies been shown to effectively function in the bloodstream of living animals," Shea says. "This technique could be utilized to make plastic nanoparticles designed to fight more lethal toxins and pathogens."

Takashi Kodama of Stanford University and Hiroyuki Koide, Takeo Urakami, Hiroaki Kanazawa and Naoto Oku of Japan's University of Shizuoka also contributed to the study, published recently in the Journal of the American Chemical Society.

Unlike natural antibodies produced by live organisms and harvested for medical use, synthetic antibodies can be created in laboratories at a lower cost and have a longer shelf life.

"The bloodstream includes a sea of competing molecules - such as proteins, peptides and cells - and presents considerable challenges for the design of nanoparticles," Shea says. "The success of this experiment demonstrates that these challenges can be overcome."