Purifying proteins:Researchers use NMR to improve drug development

  The purification of drug components is a large hurdle facing modern drug development. This is particularly true of drugs that utilize proteins, which are notoriously difficult to separate from other potentially deadly impurities. Scientists within the Center for Biotechnology and Interdisciplinary Studies (CBIS) at Rensselaer Polytechnic Institute are using nuclear magnetic resonance (NMR) to understand and improve an important protein purification process.

"We hope to use our insights to help those in the industry develop improved processes to provide much less expensive drugs and dramatically reduce healthcare costs," said paper author and William Weightman Walker Professor of Polymer Engineering Steven Cramer of Rensselaer.

His team's findings are published in the Sept. 2 online early edition of the journal Proceedings of the National Academy of Sciences (PNAS) in a paper titled "Evaluation of protein absorption and preferred binding regions in multimodal chromatography using NMR." The research was funded by the National Science Foundation (NSF).

The process of multimodal chromatography has recently generated significant interest in the pharmaceutical industry. At its most basic, this process separates proteins from their surrounding materials, such as DNA and other proteins.

The process works by encouraging the desired protein to stick to a material that contains a ligand, a type of molecular glue. Each ligand is only attracted to certain parts of certain proteins. Having been separated from the mixture, the specific protein can now be obtained in purer form, facilitating its eventual use as a biotherapeutic

The more selective the ligand is at binding to a specific protein, the more efficient the process is, and the less additional steps are required to produce the final drug. This results in reduced costs for the production of the drug. But despite its widespread use and benefits, there is very little understood about how the process actually works or how the ligands can be improved.

"We are trying to understand what exactly is making these materials so useful forseparating proteins," Cramer said. "And what we are looking to uncover are the fundamental interactions within the chromatographic process that make the separations possible and efficient."


Enlarge

This is the 800MHZ Nuclear Magnetic Resonator at Rensselaer Polytechnic Institute. Credit: Rensselaer Polytechnic Institute

For this study, the researchers used several of the advanced research facilities within CBIS. Using the Microbiology and Fermentation Core, Cramer and his colleagues grew several mutants of a protein called ubiquitin.

This group of modified proteins is referred to as a protein library.
To compare the difference between multimodal systems and more traditional chromatography, the team ran the library through a less sophisticated chromatography system called ion exchange chromatography, as well as the multimodal system. They found that there was very little to no difference in the binding of proteins to ligands in the traditional ion exchange system.

In contrast, there were huge fluctuations in the binding of some of the different mutants within the multimodal system.
To delve further into why this happened, they input ubiquitin and the multimodal ligands into the massive 800 megahertz NMR at Rensselaer's CBIS. The NMR uses magnetic properties within organic materials to provide information on the minute molecular chemical properties of the material.

From the NMR data, they were able to determine what part and type of the protein the ligands were binding to and how strongly they would bind. Their results validated the previous multimodal chromatography comparison experiments, showing that each of the protein mutants that strongly fluctuated in their binding strength in the multimodal chromatographic system were also the same ones identified with the NMR.

 physorg

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New ways to fight bacteria

 

As bateria develop resistance to antibiotics, researchers look for weapons in viruses, pharmabiotics, frog skins, cockroach brains, the human immune system and disarming compounds.

But inside the body, pharmabiotics can, like phage, evolve in step with disease-causing bacteria, so it should be hard for the bad bacteria to dodge the treatment.

Filutowicz, too, is toying with good bacteria that can seek out the nasty ones and either pump them full of antibiotics or force them to produce the antibiotics themselves. He founded a company, ConjuGon Inc., to develop his ideas. In a 2007 paper in the Journal of Burn Care & Research, Filutowicz reported that his pharmabiotics successfully knocked down infection and promoted survival in mice with infected burns.

Many current antibiotics come from bacteria or fungi that need to fight off neighboring microbes. Now, scientists are casting a wider net in their search for new antimicrobial agents — including looking in animals, such as frogs, that are very good at fighting off bacteria.

Michael Conlon, a chemist at the United Arab Emirates University in Al-Ain, invites colleagues to send him samples of the chemicals frogs secrete on their skin so he can test their antibacterial activity.

"People think I'm some kind of lunatic," Conlon says. "Why on earth would you ever look in frog skin for antibiotics?"

The reason is that frogs live in warm, wet environments, making their skin an appealing home for bacteria. So frogs have evolved an arsenal of bacteria-killing chemicals to protect themselves.

At the August meeting of the American Chemical Society in Boston, Conlon reported that he has amassed a collection of skin secretions from more than 6,000 kinds of frogs. He has found more than 100 frog slime compounds that attack bacteria. "They just rip big holes in the cell membrane," Conlon says.

Fighting off the frog bactericides will require larger evolutionary changes than bacteria needed to resist current antibiotics, so it should take a while before they manage to resist the new drugs.

Conlon is not the only scientist thinking beyond the ordinary in his hunt for new antibiotics. Frog skin sounds positively reasonable compared to what scientists at the University of Nottingham in the U.K. are exploring. At the September meeting of the Society for General Microbiology in Nottingham, Simon Lee presented work on antimicrobials he and colleagues found in the brains of cockroaches and locusts.

The bugs, after all, live in pretty dirty environments and need to prevent infection. The researchers found that the insect tissues killed more than 90% of the bacterium methicillin-resistant Staphylococcus aureus, better known as MRSA.

The immune system

While some scientists look outward, other scientists are looking inward at how the human body naturally fights infection. At the September Interscience Conference on Antimicrobial Agents and Chemotherapy in Boston, scientists discussed a new kind of antibiotic based on human defensive weaponry that destroys the bacteria's membrane.

Because the membrane is such a complex part of the cell, it is unlikely that bacteria will quickly evolve ways to disable or avoid the drugs, says Richard Scott, vice president for research at PolyMedix Inc. in Radnor, Pa.

PolyMedix is designing chemicals that mimic the shape and action of bacteria-fighting proteins called defensins. They hope to target MRSA, for which only a couple of antibiotics are now effective.

PolyMedix researchers have already shown that their pseudo-defensin treats infections in animals. The drug appeared safe in a trial involving 77 healthy people; the main side effect was a tingling in the fingers and toes. The company hopes to soon test the drug in people with MRSA infections, Scott says.

Disarming

Menachem Shoham, a biochemist at Case Western Reserve University in Cleveland, isn't interested in killing bacteria such as MRSA. He hopes to simply disarm them.

Staph bacteria are quite common. In fact, Shoham says, one-third of us live comfortably with harmless staph in our bodies. But occasionally, those harmless bacteria start to produce toxins that destroy blood cells and cause disease.

Shohan is focusing on a bacterial gene, called AgrA, that bacteria need to make toxins. He has found a handful of compounds that block AgrA and protect blood cells, he reported at the ICAAC meeting.

Shoham's idea is to use these drugs not to stop the infection but to decrease its severity. Then, he expects, the patient's immune system can take over and cure the disease.

The drugs wouldn't kill the bacteria, so there's little incentive to develop resistance, Shohan says.

Ongoing battle

But ultimately, bacteria will come up with a way to beat even the most clever of human drug designers.

"As long as we are on this planet," Filutowicz says, "we will need new ideas and new antibiotics to confront bacteria."

latimes 

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Hepatitis C virus faces new weapon!!!!

In recent human trials for a promising new class of drug designed to target the hepatitis C virus (HCV) without shutting down the immune system, some of the HCV strains being treated exhibited signs of drug resistance.

In response, an interdisciplinary team of Florida State University biologists, chemists and biomedical researchers devised a novel genetic screening method that can identify the drug-resistant HCV strains and the molecular-level mechanisms that make them that way -- helping drug developers to tailor specific therapies to circumvent them.

The potentially life-saving technology also works when screening other viruses with drug-resistance issues, notably human immunodeficiency virus (HIV) and influenza.
More than 170 million people worldwide are infected with HCV, which leads to both acute and chronic liver diseases.

"In collaboration with pharmaceutical firm Gilead Sciences and researchers from the University of Heidelberg (Germany), what our research team discovered was how the latest drug for HCV works and what changes in the virus that makes it resistant to this unique therapy," said Hengli Tang, a Florida State University molecular biologist.

"This is knowledge that is essential to drug developers focused on HCV," said Tang, "but equally important is that our method, which we call 'CoFIM' (Cofactor-independent mutant) screening, can also be applied to other drug targets and other viruses.
"And, since we now understand how this latest class of drug works and what causes resistance to it, we can better select other classes of drugs with distinct mechanisms -- in other words, those that target other parts of the virus -- in order to craft a combination therapy, which is the future of HCV therapy and the key to overcoming drug resistance."

The groundbreaking research is described in a paper published online in the September 2010 issue of the journal PLoS Pathogens.
 
Florida State biology doctoral student Feng Yang led the research team. The award-winning scholar earned her Ph.D. in August 2010 and is now a postdoctoral associate at Yale University. Yang designed the CoFIM screening methodology with fellow FSU graduate students, postdoctoral associates and distinguished faculty colleagues -- including Associate Professor Tang; chemistry/biochemistry Professor Timothy M. Logan, director of FSU's Institute of Molecular Biophysics; and Research Assistant Professor Ewa A. Bienkiewicz, of the FSU College of Medicine, where she directs the Biomedical Proteomics Laboratory.

Driving the team's development of CoFIM screening was the need to identify key "cellular cofactors" and their mechanisms of action -- a fundamental aspect of virus-host interaction research.
"'Cellular cofactors' are proteins that normally exist in host cells that have been hijacked by viruses to facilitate viral replication." Tang said. "They became accomplices to the invading viruses.
"Our research team was the first to show that 'cyclophilin A' (CyPA) is an essential cellular cofactor for hepatitis C virus infection and the direct target of a new class of clinical anti-HCV compounds, which include cyclosporine A (CsA)-based drugs that are devoid of immunosuppressive function," Tang said.
"In addition, we went a step further than other research teams by employing our newly developed CoFIM screening method, which we used to demonstrate not only HCV's dependence on cellular cofactor cyclophilin A and susceptibility to cyclosporine A drugs but also to uncover the molecular-level regulators that determine those two traits in the virus."

Those molecular-level regulators are known as "small interfering RNA libraries" -- collections of molecules so named for their size and ability to suppress gene expression. They act to individually suppress every gene in the cell, resulting in different consequences depending upon which gene is suppressed by a given member in the library.

The CoFIM screening method involves inducing or "coaxing" the HCV virus to mutate by itself, in vitro, absent the replication assistance it normally receives from a particular cellular cofactor. Then, CoFIM tracks the changes in the virus's response both to CsA-based drugs and any other drug designed to inhibit the cofactor.

physorg 

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Superconducting trio get entangled

Entangling three qubits Santa Barbara style

Two independent teams of physicists in the US have entangled three superconducting quantum bits (qubits) for the first time. Entangled trios are of particular interest to those building quantum computers because three is the minimum number needed to do quantum error correction – which is needed to keep quantum computers running. 

Despite the promise of outperforming conventional computers on certain tasks, quantum computers can only be useful if physicists can work out how to entangle a relatively large number of qubits. So far researchers have managed to entangle as many as eight ion qubits and 10 photon qubits. But when it comes to entangling superconducting qubits, the limit so far has been just two.

Although they are difficult to entangle, superconducting qubits could have several advantages. In particular, they are completely solid state, which means that they are robust and can be implemented much like conventional electronic devices.

The new trios of entangled superconducting qubits were created by John Martinis and colleagues at the University of California, Santa Barbara, and by Robert Schoelkopf and his team at Yale University. The Santa Barbara team had previously devised a way of entangling two superconducting qubits back in 2006, while last year the Yale researchers had executed several quantum-computing algorithms using two entangled superconducting qubits.

Entangled transmons

The Yale physicists used qubits called "transmons". Each transmon is made from two tiny pieces of superconductor connected by two tunnel junctions. The superconductors contain a large numbers of "Cooper pairs" of electrons that can move through the material without any electrical resistance.

The energy levels of the qubit are defined by the precise distribution of Cooper pairs between the two pieces of superconductor. One such energy state is denoted a logical "0" and another state "1". Transitions between these two states occur by absorbing or emitting a microwave photon.

The Yale team made a chip containing four transmons that are coupled to a microwave waveguide. The four transmons are arranged as two two-qubit controlled-phase (C-phase) logic gates.

How it's done at Yale

Making a GHZ state

The gates are used to entangle three of the qubits and create a Greenberger–Horne–Zeilinger (GHZ) state. This is a superposition of the state in which all three qubits are "0" and the state in which all three qubits are "1". The GHZ state is made by first entangling two qubits using one C-phase gate. The other gate is then used to entangle the third qubit with the entangled pair.

The team verified the entanglement using quantum-state tomography. This involves creating the GHZ state, measuring the values of the qubits – and then repeating the entire process many times over. This is necessary because an individual measurement of the qubits puts the system into one of many possible states. Multiple measurements are needed to map out the probability that the system is in a certain state.

Oscillating phase

Meanwhile in Santa Barbara, Martinis, Matthew Neeley and colleagues used superconducting phase qubits to achieve three-qubit entanglement. A phase qubit is a single Josephson junction, which comprises two pieces of superconducting metal separated by a very thin insulating barrier. The two logic levels are defined by quantum oscillations of the phase difference between the electrodes of the junction.

The team created its GHZ state using a similar technique to the Yale group – except that it configured the microwave circuit to form two controlled NOT (CNOT) gates rather than C-phase gates.

The Santa Barbara group then reconfigured its circuit to create another type of entangled state called the "W" state. This is a superposition of the three states in which one of the three qubits is "1" and the other two qubits are "0". "To create this state we excite just one qubit, putting a single quantum of energy into the system," explains Neeley. "We then turn on a coupling interaction between all the pairs of qubits, which spreads that one excitation out among the three qubits."

This interaction is created by connecting the qubits together using a network of capacitors

physicsworld 

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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.

 physorg

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Graphene makes 'supercapacitor'!!

Graphene nanosheet electrode

Researchers in the US have made the first high-frequency AC "supercapacitors" containing graphene electrodes.
The devices, which are much smaller than conventional capacitors, could be used in applications like computer processing units and other tiny integrated circuits.
Capacitors are devices that store electric charge. "Supercapacitors", more accurately known as electric double-layer capacitors (DLCs) or electrochemical capacitors, can store much more charge thanks to the double layer formed at an electrolyte-electrode interface when voltage is applied.

Commercial DLCs are extremely powerful when compared with batteries but they are essentially DC devices – that is, they take several seconds to fully charge and then several seconds to fully discharge again.

They operate efficiently at frequencies below about 0.05 Hz and are therefore good for applications like hybrid vehicles, which can take up to 10 seconds to charge (when braking) and 10 seconds to discharge (when accelerating).

However, at higher frequencies, they become much less efficient and start to behave like resistors rather than capacitors. This is because the devices usually contain porous electrodes made from a high-surface-area conductive material, such as activated carbon, and the pores increase the resistance of devices.


Now, John R Miller and colleagues of JME Inc. in Shaker Heights and Case Western Reserve University, Cleveland, both in Ohio, have overcome this problem by developing the first DLC that contains vertically oriented high-surface-area graphene electrodes that aren't porous at all. The device pushes the operating frequency of an electric double layer capacitor to well beyond 5000 Hz, which is a factor of 10⁵ better than commercial DLCs.

What's more, it is six times smaller than low-voltage aluminium electrolytic capacitors and can be charged and discharged at high efficiency in times much shorter than 1 ms.

The researchers grew the graphene – 2D sheets of carbon just one atom thick – on a metal using a plasma-assisted chemical vapour deposition process
Such vertically oriented graphene sheets are ideal in terms of structure for high-frequency DLC electrode applications, says the team. They have many edge planes that can provide between 50 and 70 µF/cm² of capacitance compared with basal planes, which only provide 3 µF/cm². These charge-storage edge planes are highly exposed and can thus be accessed directly, which means that charge can be stored over precise areas rather than being dispersed over larger regions.

And last but not least, the nanosheet "stacked" structure ensures that pores are reduced – so minimizing resistance – and the sheets themselves are highly conducting.
"The bottom line is that these devices could lead to smaller higher-frequency capacitors for applications in low-voltage systems like CPUs and similar integrated circuits, physicsworld

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Five minute drugs test 'can tell parents if their children use cocaine'

Scientists say it has been proven to highlight the smallest amount of a drug such as a metabolite (small molecules) of cocaine. Photo: PA

Researchers have unveiled the £1.50 test, which takes five minutes and detects other illegal substances.

The disposable drugs test analyses a droplet of saliva for any trace of drugs in a person's system.

Scientists say it has been proven to highlight the smallest amount of a drug such as a metabolite (small molecules) of cocaine.

Suspicious parents can screen their children for the drugs by taking a swab of their saliva and placing it into a machine.

The Vantix biosensor technology, developed by Universal Sensors Ltd, could also be used by police officers to test motorists for drugs by the roadside.

Kevin Auton, Commercial Director of Universal Sensors, admitted the tests could have ''huge implications for society''.

"It is controversial but the test can be used in the home for worried parents to test if their children are taking drugs," he said.

''We are very focused on getting the test out of the laboratory and onto other platforms. It is as simple to use as a pregnancy test.

''We can produce 30 million biosensors each year, which means it is very cheap to sell.''

The tests, developed at Universal Sensors' base in Ickleton, Cambs., are designed to be used in the home.

But they could also be rolled out across the country to aid police investigating suspected drug drivers.

Currently, officers perform Field Impairment Tests, which look at pupil dilation, balance and coordination.

These are not solid proof of illegal driving and police are often reluctant to carry out time consuming blood tests.

The breakthrough means officers would be able to identify drugs by taking a swab from a driver's mouth.

They would then place the sample into a machine and the result would be returned just five minutes later.

Drugs are considered a contributing factor is three percent of death on British roads - but this is likely to be underestimated due to the difficulty in detecting substances.

A spokesman for Universal Sensors Ltd said police did often not go on to test for drugs in drink drivers as the procedure was so time consuming.

''Drugs and alcohol are often consumed simultaneously, but once the police have detected alcohol they are unlikely to go to the effort of drug testing," he said.

''The VantixTM biosensor has the potential to provide police with a straightforward, unambiguous test result, which would help identify drug drivers and secure convictions.

''Such a sensitive technology would make a zero tolerance approach to drug drivers possible for the first time."

He added: "'A test which can be performed on untreated saliva by a member of the police force would save police time and resources, and increase the proportion of drug driver convictions, making the roads safer for all.''

telegraph

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Entangled frameworks limber up

The degree of interconnectivity of molecular frameworks in microporous materials influences their structural flexibility and gas sorption

Schematic representations of the synthesis

of 2D&3D 

interpenetrated porous 

Coordination polymers,

 

The quest to tune the three-dimensional (3D) molecular frameworks of materials called porous coordination polymers (PCPs) has taken a step forward thanks to a research team led by Ryotaro Matsuda and Susumu Kitagawa at the RIKEN SPring-8 Center in Harima and Kyoto University, Japan. The team, with members from Osaka Prefecture University, has described the influence of interpenetration of PCPs on the structural flexibility and gas sorption behavior of these materials1, which show great potential for use in gas storage, heterogeneous catalysis and as separation materials.

The interpenetrated molecular frameworks of PCPs are composed of metal ions and bridging organic ligands. Materials scientists initially thought that interpenetration would reduce the available capacity of the voids within the structure. However, other researchers showed recently that such entangled structures exhibit high gas-uptake, as a result of increased internal surface area. Interpenetration also increases the thermal stability of flexible frameworks.

These findings prompted Matsuda, Kitagawa and colleagues to make PCPs with the same chemical components but with either two-fold or three-fold interpenetration. Both forms of the 3D frameworks were made using a solvent templating method and were composed of zinc atoms and carboxylate- and pyridyl-based organic ligands (Fig. 1). The two forms allowed the researchers to test the correlation between various physical properties and the degree of entanglement of the polymers.

Crystal structure analyses of the two forms indicated that non-covalent interactions, namely π-π interactions, in the three-fold structure are more significant than in the two-fold structure. Consequently, the two-fold structure has a more flexible structure and is of lower thermal stability than the more rigid three-fold PCP.

Using coincident x-ray powder diffraction and adsorption measurements, the team also showed that the two forms of structures have completely different carbon dioxide (CO₂) adsorption behavior. The two-fold structure can adsorb four times the amount of saturated CO₂ than the three-fold structure, owing to its greater flexibility and dynamic capability. Sorption occurs as a stepwise progression as a result of crystallographic transformations triggered by the addition and removal of guest molecules.

“The next challenge is the control of adsorption properties by external stimuli such as light or magnetic field to realize on-demand gas separation and storage,” says Matsuda. “This kind of material could be used to separate CO2 which is discharged from steelworks or to remove CO₂ and hence keep air fresh in a spaceship.”

physorg 

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Ingredient in soap points toward new drugs for toxoplasmosis infection

The antibacterial ingredient in some soaps, toothpastes, odor-fighting socks, and even computer keyboards is pointing scientists toward a long-sought new treatment for a parasitic disease that affects almost two billion people. Their report on how triclosan became the guiding light for future development of drugs for toxoplasmosis appears in ACS' monthly Journal of Medicinal Chemistry.

In the study, Rima McLeod and colleagues point out that toxoplasmosis is one of the world's most common parasitic infections, affecting about one-third of the world population, including 80 percent of the population of Brazil. People can catch the infection, spread by the parasite Toxoplasma gondii (T. gondii), from contact with feces from infected cats, eating raw or undercooked meat, and in other ways.

Many have no symptoms because their immune systems keep the infection under control and the parasite remains inactive. But it can cause eye damage and other problems, even becoming life threatening in individuals with immune systems weakened by certain medications and diseases like HIV infection, which allow the parasite to become active again, and in some persons without immune compromise. Most current treatments have some potentially harmful side effects and none of them attack the parasite in its inactive stage.

The scientists knew from past research that triclosan has a powerful effect in blocking the action of a key enzyme that T. gondii uses to live. Triclosan, however, cannot be used as a medication because it does not dissolve in the blood. 

The scientists describe using triclosan's molecular structure as the model for developing other potential medications, including some that show promise as more effective treatments for the disease.

physorg

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Fruit flies help scientists sniff out new insect repellents

By following the "nose" of fruit flies, Yale scientists are on the trail of new insect repellents that may reduce the spread of infectious disease and damage to agricultural crops. That's because they've learned for the first time how a group of genes used to differentiate smells is turned on and off, opening new possibilities for insect control.

Just as in new drug development, researchers can target these or similar genes in other insects to create substances that make crops and people "invisible" to insect antennae.

Without the ability to smell correctly, the insects are far less likely to attack a person or plant, as is the case with mosquitoes whose ability to smell lactic acid is disrupted by the active ingredient in insect repellents, DEET. This finding is reported in the September 2010 issue of the journal Genetics.

According to Carson Miller, a researcher involved in the work from the Department of Molecular, Cellular and Developmental Biology at Yale University, "One of the fundamental questions in biology is, 'how does a cell choose which genes it should turn on and which genes it should turn off?' By studying this question in odor-sensitive neurons of fruit flies, we hope to learn how cells make these choices, as well as to develop more effective odor-based insect repellents."
The scientists studied four genes from a group of odor receptor genes in the fruit fly.

These genes afford flies the ability to detect different scents. Pieces of DNA in front of these genes contained enough information to tell the fly to turn on these genes in specific cells of the antenna.

Miller made an artificial reporter gene that used the regulatory DNA in front of an Odor receptor gene to control a test gene that could be easily monitored for expression. An entire set of such reporter genes were created, each containing less of the regulatory DNA. The goal was to determine how short the regulatory region could be and yet still control the test gene normally.

This helped Miller to identify where the important control elements lie in the regulatory DNA, and whether they serve to turn the gene on in cells where it is needed or to turn the gene off where it doesn't belong.

"The sense of smell is an Achilles heel for many insects," said Mark Johnston, Editor-in-Chief of the journal GENETICS, "and the more we learn about odor receptors the easier it will be to interfere with them to battle insect-borne disease and crop devastation. This study is a step forward in doing that by identifying the mechanism that results in the highly selective expression of 'smell genes'."
physorg

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Nano antenna concentrates light

Intensity increases 1,000-fold in Rice lab's experiment

Everybody who's ever used a TV, radio or cell phone knows what an antenna does: It captures the aerial signals that make those devices practical. A lab at Rice University has built an antenna that captures light in the same way, at a small scale that has big potential. 

Condensed matter physicist Doug Natelson and graduate student Dan Ward have found a way to make an optical antenna from two gold tips separated by a nanoscale gap that gathers light from a laser. The tips "grab the light and concentrate it down into a tiny space," Natelson said, leading to a thousand-fold increase in light intensity in the gap.
 
Getting an accurate measurement of the effect is a first, said Natelson, who reported the results in the online edition of the journal Nature Nanotechnology. He expects the discovery will be useful in the development of tools for optics and for chemical and biological sensing, even at the single-molecule scale, with implications for industrial safety, defense and homeland security.
 
The paper by Natelson, Ward and their colleagues in Germany and Spain details the team's technique, which involves shining laser light into the gap between a pair of gold tips less than a nanometer apart - about a hundred-thousandth the width of a human hair.
 
"You can ignore the fact that your car antenna is built out of atoms; it just works," said Natelson, a Rice professor of physics and astronomy, and also electrical and computer engineering. "But when you have tiny pieces of metal very close to each other, you have to worry about all the details. The fields are going to be big, the situation's going to be complicated and you're really constrained. We've been able to use some physics that only come into play when things are very close together to help figure out what's going on."
 
The key to measuring light amplification turned out to be measuring something else, specifically the electrical current flowing between the gold tips.
 
Putting the nanotips so close together allows charge to flow via quantum tunneling as the electrons are pushed from one side to the other. The researchers could get electrons moving by pushing them at low frequencies with a voltage, in a highly controllable, measurable way. They could also get them flowing by shining the laser, which pushes the charge at the very high frequency of the light. Being able to compare the two processes set a standard by which the light amplification could be determined, Natelson said. Their German and Spanish coauthors helped supply the necessary theoretical justification for the analysis.
 
The amplification is a plasmonic effect, Natelson said. Plasmons, which may be excited by light, are oscillating electrons in metallic structures that act like ripples in a pool. "You've got a metal structure, you shine light on it, the light makes the electrons in this metal structure slosh around," he said. "You can think of the electrons in the metal as an incompressible fluid, like water in a bathtub. And when you get them sloshing back and forth, you get electric fields.
 
"At the surfaces of the metal, these fields can be very big - much bigger than those from the original radiation," he said. "What was hard to measure was just how big. We didn't know how much the two sides were sloshing up and down - and that's exactly the thing we care about."
 
By simultaneously measuring the low-frequency electrically driven and the high-frequency optically driven currents between the tips, "we can figure out the voltage zinging back and forth at the really high frequencies that are characteristic of light," he said.
 
Natelson said his lab's homebuilt apparatus, which combines nanoscale electronics and optics, is fairly unusual. "There are a lot of people who do optics. There are a lot who do nanoscale electrical measurements," he said. "There are still not too many people who combine the two."
 
The custom rig gave the Rice researchers a measure of control over thermal and electrical properties that have stymied other investigators. The tips are cooled to 80 Kelvin, about -315 degrees Fahrenheit, and are electrically insulated from their silicon bases, keeping at bay stray voltages that could skew the results.
 
"The reason we're studying these enhanced fields is not just because they're there," Natelson said. "If you can enhance the local field by a factor of 1,000, there are lots of things you can do in terms of sensors and non-linear optics. Anything that gives you a handle on what's happening at these tiny scales is very useful.
 chemie

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Nano-Vehicle acts as cluster bomb for tumors

Chemotherapy, while an effective cancer treatment, also brings debilitating side effects such as nausea, liver toxicity, and a battered immune system. Now, a new way to deliver this life-saving therapy to cancer patients -- getting it straight to the source of the disease -- has been developed by Dan Peer and Rimona Margalit and their colleagues at Tel Aviv University.

Drs. Peer and Margalit have developed a nano-sized vehicle with the ability to deliver chemotherapy drugs directly into cancer cells while avoiding interaction with healthy cells, increasing the efficiency of chemotherapeutic treatment while reducing its side effects.

"The vehicle is very similar to a cluster bomb," explains Dr. Peer. Inside the nano-vehicle itself are nanoparticles loaded with chemotherapy drugs. When the delivery vehicle, comprising multiple nanoparticles, comes into contact with cancer cells, it releases the chemotherapeutic payload directly into the cell. According to Dr. Peer, the nanoparticle device can be used to treat many different types of cancer, including lung, blood, colon, breast, ovarian, pancreatic, and even several types of brain cancers. A paper describing their new nanoparticles and their use in targeting tumors appears in the journalBiomaterials.

The key to the drug delivery platform is hyaluronan, the molecule used to create the outer coating of this clustered nanoparticle. Hyaluronan is a sugar recognized by receptors on many types of cancer cells. "When the nano-vehicle interacts with the receptor on the cancerous cell, the receptor undergoes a structural change and the chemotherapy payload is released directly into the cancer cell," says Dr. Peer. The result, he explains, is a more to more focused chemotherapeutic treatment against the diseased cells.

Because the nanoparticle reacts only with cancer cells, the healthy cells that surround them remain untouched and unaffected by the therapy. The nano-vehicle itself, adds Dr. Peer, is made from naturally occurring lipid molecules that decompose in the body once the nanoparticles have performed their function, making the treatment potentially safer than current therapies. Tests with tumor-bearing mice showed that hyaluronan-coated nanoparticles filled with paclitaxel were more effective than either free paclitaxel or Abraxane—an albumin nanoparticle loaded with paclitaxel—at stopping tumor growth.physorg

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Nanoparticle-decorated cells power novel approach to cancer therapy

clinical trials using patients' own immune cells to target tumors have yielded promising results. However, this approach usually works only when patients also receive large doses of drugs designed to help immune cells multiply rapidly, and those drugs have life-threatening side effects. Now a team of MIT engineers has devised a way to deliver the necessary drugs by smuggling them within nanoparticles that are attached to the cells sent in to fight the tumor. As a result, the immune cell stimulating drug reaches only its intended targets, greatly reducing the risk to the patient.

The new approach could dramatically improve the success rate of immune-cell therapies, which hold promise for treating many types of cancer, says Darrell Irvine. Dr. Irvine led the team that published its results in the journal Nature Medicine. "What we're looking for is the extra nudge that could take immune-cell therapy from working in a subset of people to working in nearly all patients, and to take us closer to cures of disease rather than slowing progression," said Dr. Irvine. The new method could also be used to deliver other types of cancer drugs or to promote blood-cell maturation in bone-marrow transplant recipients, according to the researchers.


To perform immune-cell therapy, doctors remove a type of immune cell called T cells from the patient, engineer them to target the tumor, and inject them back into the patient. Those T cells then hunt down and destroy tumor cells. Clinical trials are under way in which immune-cell therapy is being tested in patients with ovarian and prostate cancers, as well as melanoma.


Immune-cell therapy is a very promising approach to treating cancer, but getting it to work has proved challenging. The major limitations today include procuring enough of the T cells that are specific to the cancer cell and then getting those T cells to function properly in the patient. To overcome those obstacles, researchers have tried injecting patients with adjuvant drugs that stimulate T-cell growth and proliferation. The interleukins—naturally occurring chemicals that help promote T-cell growth—have produced promising results in human clinical trials, but interleukin therapy can produce severe side effects, including heart and lung failure, when infused into the blood stream in large doses.


Dr. Irvine and his colleagues took a new approach: To avoid toxic side effects, they turned to lipid-based nanoparticles that they can attach to sulfur-containing molecules normally found on the T-cell surface. The investigators loaded two interleukins - IL-15 and IL-21 - into the nanoparticles, and then injected the nanoparticle-T cell combo into mice with lung and bone marrow tumors. Once the cells reached the tumors, the nanoparticles gradually degraded and released the drug over a week-long period. The drug molecules attached themselves to receptors on the surface of the same cells that carried them, stimulating them to grow and divide.


Within 16 days, all of the tumors in the mice treated with T cells carrying the drugs disappeared. Those mice survived until the end of the 100-day experiment, while mice that received no treatment died within 25 days, and mice that received either T cells alone or T cells with injections of interleukins died within 75 days.


Dr. Irvine and his colleagues also demonstrated that they could attach their nanoparticles to the surface of immature blood cells found in the bone marrow, which are commonly used to treat leukemia. Patients who receive bone-marrow transplants must have their own bone marrow destroyed with radiation or chemotherapy before the transplant, which leaves them vulnerable to infection for about six months while the new bone marrow produces blood cells. Delivering drugs that accelerate blood-cell production along with the bone-marrow transplant could shorten the period of immunosuppression, making the process safer for patients, says Dr. Irvine. In the Nature Medicinepaper, his team reports successfully enhancing blood-cell maturation in mice by delivering one such drug along with the cells.
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Physicists control chemical reactions mechanically

 

UCLA physicists have taken a significant step in controlling chemical reactions mechanically, an important advance in nanotechnology, UCLA physics professor Giovanni Zocchi and colleagues report.

Chemical reactions in the cell are catalyzed by enzymes, which are proteinmolecules that speed up reactions. Each protein catalyzes a specific reaction. In a chemical reaction, two molecules collide and exchange atoms; the enzyme is the third party, the "midwife to the reaction."

But the molecules have to collide in a certain way for the reaction to occur. The enzyme binds to the molecules and lines them up, forcing them to collide in the "right" way, so the probability that the molecules will exchange atomsis much higher.

"Instead of just watching what the molecules do, we can mechanically prod them," said Zocchi, the senior author of the research.

To do that, Zocchi and his graduate students, Chiao-Yu Tseng and Andrew Wang, attached a controllable molecular spring made of DNA to the enzyme. The spring is about 10,000 times smaller than the diameter of a human hair. They can mechanically turn the enzyme on and off and control how fast the chemical reaction occurs. In their newest research, they attached the molecular spring at three different locations on the enzyme and were able to mechanically influence different specific steps of the reaction.

They published their research in the journal Europhysics Letters, a publication of the European Physical Society, in July.

"We have stressed the enzyme in different ways," Zocchi said. "We can measure the effect on the chemical reaction of stressing the molecule this way or that way. Stressing the molecule in different locations produces different responses. If you attach the molecular spring in one place, nothing much happens to the chemical reaction, but you attach it to a different place and you affect one step in the chemical reaction. Then you attach it to a third place and affect another step in this chemical reaction."

Zocchi, Tseng and Wang studied the rate of the chemical reactions and reported in detail what happened to the steps of the reactions as they applied mechanical stress to the enzyme at different places.



"Standing on the shoulders of 50 years of structural studies of proteins, we looked beyond the structural description at the dynamics, specifically the question of what forces — and applied where — have what effect on the reaction rates," Zocchi said.

In a related second paper, Zocchi and his colleagues reached a surprising conclusion in solving a longstanding physics puzzle.

When one bends a straight tree branch or a straight rod by compressing it longitudinally, the branch or rod at first remains straight and does not bend until a certain critical force is exceeded. At the critical force, it does not bend a little — it suddenly buckles and bends a lot.

"This phenomenon is well known to any child who has made bows from hazelnut bush branches, for example, which are typically quite straight. To string the bow, you have to press down on it hard to buckle it, but once it is bent, you need only a smaller force to keep it so," Zocchi said.

The UCLA physicists studied the elastic energy of their DNA molecular spring when it is sharply bent.

"Such a short double-stranded DNA molecule is somewhat similar to a rod, but the elasticity of DNA at this scale was not known," Zocchi said. "What is the force the DNA molecular spring is exerting on the enzyme? We have answered this question.

"We find there is a similar bifurcation with this DNA molecule. It goes from being bent smoothly to having a kink. When we bend this molecule, there is a critical force where there is a qualitative difference. The molecule is like the tree branch and the rod in this respect. If you're just a little below the threshold, the system has one kind of behavior; if you're just a little above the threshold force, the behavior is totally different. The achievement was to measure directly the elastic energy of this stressed molecule, and from the elastic energy characterize the kink."

Co-authors on this research are UCLA physics graduate students Hao Qu, Chiao-Yu Tseng and Yong Wang and UCLA associate professor of chemistry and biochemistry Alexander Levine, who is a member of the California NanoSystems Institute at UCLA. The research was published in April, also in the journal Europhysics Letters.

"We can now measure for any specific DNA molecule what the elastic energy threshold for the instability is," Zocchi said. "I see beauty in this important phenomenon. How is it possible that the same principle applies to a tree branch and to a molecule? Yet it does. The essence of physics is finding common behavior in systems that seem very different."

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Scientists generate rotating electron beams

A team of EU-funded scientists has come up with a way of generating rotating electron beams. The technique, described in the journalNature, could be used to probe the magnetic properties of materials and could even be applied to manipulate minute particles and set them in motion.

Beams of electrons have been used to study matter for many years - transmission electron microscopes (TEMs) are now commonplace in laboratories worldwide. However, a normal beam of electrons does not provide researchers with information on the magnetic properties of an object. For this a vortex beam of electrons, which rotates in a similar way to the air flow in a tornado, is needed.

Vortex light beams have existed for some time and are used in applications such as micro-motors and 'optical tweezers', allowing scientists to manipulate micrometre-scale particles. A vortex beam of electrons would provide scientists with a tool to manage nanoparticles, but generating such a vortex beam has proven rather difficult.

Earlier this year, a team from Japan succeeded in creating an electron beam with a twist. Their technique entailed producing graphite sheets and then looking for a spot where two or more layers happen to be aligned in such a way that a spiral structure is created. This spiral structure is then able to impart a twist to an electron beam passing through it. In theory, a similar structure could be created artificially, but in practice this is extremely difficult as it requires nanometre-scale machining.

In this latest study, scientists from the University of Antwerp in Belgium and the Technical University of Vienna in Austria took a different approach to the problem. The team created a grid-like 'mask' in a sheet of platinum foil 100 nanometres thick. The mask included transparent and opaque regions that allowed electrons through or blocked them respectively. When an electron beam is directed at the mask, it is diffracted, just as a beam of light is diffracted when it passes through a fine grid. The shape of the grid is carefully designed to turn ordinary electron beams into vortex beams. Crucially, because the grid's dimensions are measured in micrometres rather than nanometres, it is relatively easy to make.

'This technique is a reproducible method of creating vortex electron beams in a conventional electron microscope,' the researchers write. 'We demonstrate how they may be used in electron energy-loss spectroscopy to detect the magnetic state of materials and describe their properties. Our results show that electron vortex beams hold promise for new applications, in particular for analysing and manipulating nanomaterials, and can be easily produced.'

Professor Peter Schattschneider of the Technical University of Vienna is one of the authors of the paper. 'These electron beams could be used in a targeted way to set tiny wheels in motion on a microscopic motor,' he points out. 'Also, the magnetic field of the rotating electrons could be used in the tiniest length scales.' It may ultimately be possible to apply this technology to data transfer (quantum cryptography) and in quantum computers.

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Optical Chip Enables New Approach to Quantum Computing

An international research group led by scientists from the University of Bristol has developed a new approach to quantum computing that could soon be used to perform complex calculations that cannot be done by today's computers.

Scientists from Bristol's Centre for Quantum Photonics have developed a silicon chip that could be used to perform complex calculations and simulations using quantum particles in the near future. The researchers believe that their device represents a new route to a quantum computer -- a powerful type of computer that uses quantum bits (qubits) rather than the conventional bits used in today's computers.

Unlike conventional bits or transistors, which can be in one of only two states at any one time (1 or 0), a qubit can be in several states at the same time and can therefore be used to hold and process a much larger amount of information at a greater rate.

"It is widely believed that a quantum computer will not become a reality for at least another 25 years," says Professor Jeremy O'Brien, Director of the Centre for Quantum Photonics. "However, we believe, using our new technique, a quantum computer could, in less than ten years, be performing calculations that are outside the capabilities of conventional computers."

The technique developed in Bristol uses two identical particles of light (photons) moving along a network of circuits in a silicon chip to perform an experiment known as a quantum walk. Quantum walk experiments using one photon have been done before and can even be modelled exactly by classical wave physics. However, this is the first time a quantum walk has been performed with two particles and the implications are far-reaching.

"Using a two-photon system, we can perform calculations that are exponentially more complex than before," says O'Brien. "This is very much the beginning of a new field in quantum information science and will pave the way to quantum computers that will help us understand the most complex scientific problems."

In the short term, the team expect to apply their new results immediately for developing new simulation tools in their own lab. In the longer term, a quantum computer based on a multi-photon quantum walk could be used to simulate processes which themselves are governed by quantum mechanics, such as superconductivity and photosynthesis.

"Our technique could improve our understanding of such important processes and help, for example, in the development of more efficient solar cells," adds O'Brien. Other applications include the development of ultra-fast and efficient search engines, designing high-tech materials and new pharmaceuticals.

The leap from using one photon to two photons is not trivial because the two particles need to be identical in every way and because of the way these particles interfere, or interact, with each other. There is no direct analogue of this interaction outside of quantum physics.

"Now that we can directly realize and observe two-photon quantum walks, the move to a three-photon, or multi-photon, device is relatively straightforward, but the results will be just as exciting" says O'Brien. "Each time we add a photon, the complexity of the problem we are able to solve increases exponentially, so if a one-photon quantum walk has 10 outcomes, a two-photon system can give 100 outcomes and a three-photon system 1000 solutions and so on."

The group, which includes researchers from Tohoku University, Japan, the Weizmann Institute in Israel and the University of Twente in the Netherlands, now plans to use the chip to perform quantum mechanical simulations. The researchers are also planning to increase the complexity of their experiment not only by adding more photons but also by using larger circuits.

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Scientists hail 'penicillin moment' in cancer treatment

Human melanoma cells Photo: GETTY IMAGES

Scientists have hailed a 'penicillin moment' in cancer treatment following trials of a drug that uses genetic data to target the formation of specific tumours.

The study has raised hopes drug manufacturers will be able to tailor drugs to individual cancers that will halt them in their tracks and even reverse the growth of existing tumours.

The breakthrough is one of the most significant to use advances in our knowledge of DNA to tackle the root causes of disease.

For years scientists have been assembling vast amounts of genetic information provided through the human genome sequencing project. However, a number of prominent scientists had expressed disappointment that the data had not led to any major advances in treatments.

As part of the latest research, scientists in California developed a drug to block the effects of a specific gene mutation, B-RAF, linked to malignant melanoma – one of the deadliest cancers.

In one small clinical trial, tumours shrank by at least 30 per cent in 24 out of 32 patients with B-RAF mutations, and disappeared entirely in two other patients.
The drug cannot yet be declared a success: it comes with side-effects, can only treat the specific B-RAF mutation and there are no indications of its long-term usefulness.

However, a study of the chemical process behind the drug, detailed in the journal Nature, demonstrates the potential for speedy development of similar treatments targeting the particular genetic mutations that lie behind different types of tumour.

Professor Mark Stratton, Director of the Wellcome Trust Sanger Institute in Cambridge, which first linked B-RAF to malignant melanoma, said: "We've entered an end game in which we are going to complete our understanding of what causes cancer."
Yardena Samuels, a cancer geneticist at the National Human Genome Research Institute in Bethesda, Maryland, told Nature News: "It's a very important development, not just for melanoma, but for the entire cancer field."

The company behind PLX4032, Plexxikon, is now working on a test that can diagnose which malignant melanoma patients have the B-RAF mutation and would therefore benefit from the drug.
telegraph

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Artificial ovary gives fertility hope to cancer sufferers

An artificial ovary that can mature human eggs could lend new hope to women whose fertility is at risk from cancer treatments, scientists claim.

The ovary, which was created in a laboratory from cells donated by hospital patients, can mimic a real ovary by growing over the eggs and allowing them to mature.

The researchers said the breakthrough could allow eggs to be taken from women before they were exposed to chemotherapy or radiation and then developed in the artificial structure.

Scientists hope it could also help answer questions about how ovaries work and enable experiments on what causes problems for egg maturation and health.

The researchers, from Brown University and Woman & Infants Hospital in America, grew the donor cells into honeycomb shapes before placing human egg cells in the holes.

Within days the cells had enveloped the immature eggs and they were able to grow to full maturity, according to the study in the Journal of Assisted Reproduction and Genetics.

Sandra Carson, professor of obstetrics and gynaecology at Brown University, wrote: "An ovary is composed of three main cell types, and this is the first time that anyone has created a 3-D tissue structure with triple cell line. This is really very, very new and is the first success in using 3-D tissue engineering principles."

Neil McClure, professor of Obstetrics and Gynaecology at Queen's University, Belfast, said: "This certainly has the potential to provide a very good way of maturing very immature eggs in the lab to the point where they can be used for assisted reproduction.

"There are lots of studies that need to be done but it is a huge step forward and a very novel technique that has the potential to give hope to young women who are going to be undergoing treatment which will prevent them having children naturally."

Professor Richard Fleming, director of the GCRM fertility unit in Glasgow, said the development could have "great practical implications" on fertility treatment by maturing eggs more reliably.

He said: "It is a significant step along a long pathway but really quite an important one.

"If you try to mature eggs in a Petri dish the structure tends to collapse rather than sticking to itself. This is trying to improve the proportion of the immature eggs that get through to the mature stage."

But other experts said the new development did not yet represent a ‘real’ artificial ovary" because it did not contain primordial follicles, which develop eggs in real ovaries.

Professor Bill Ledger, a fertility expert from Sheffield University, said: "We have no idea why a primordial follicle will rest for 30 years or more then decide to begin to develop and eventually release its egg. If we did, then we could try to lengthen a woman’s fertile lifespan or restore fertility to women after treatment with chemotherapy.

"The artificial structure does not contain primordial follicles, nor have they shown that it can regulate the ‘awakening’ of primordial follicles in an orderly manner, as in the normal ovary, so I don’t think its quite accurate to label it as an artificial ovary."
telegraph

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Small dose of aspirin 'can ward off bowel cancer'

A daily 75mg dose – lower than the recommended dose for a child – can provide significant protective effects after just one year, researchers said.

Even people not considered to be at high risk of the disease could benefit from taking the painkiller, they said, regardless of their diet or lifestyle.

According to the study, taking 75mg of aspirin every day for between one and three years cut the chances of developing bowel cancer by 19 per cent.

After three to five years the risk decreased by 24 per cent, and after five to ten years of taking the drug the chance of bowel cancer was down by 31 per cent.

There was no noticeable benefit in taking aspirin or any other non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, for people who already had bowel cancer.
The disease, which is the second most common cause of cancer death in the world, kills more than 16,000 people in Britain every year, with 38,500 cases diagnosed in annually.

Previous research had indicated that aspirin protects against bowel cancer, but it was unclear what the most effective dose was, and how often it should be taken.
The usual aspirin dose for an adult, when used for pain relief, is between 300mg and 900mg.
NSAIDs have previously been linked to an increased risk of internal bleeding.

But the study of 2,800 people with bowel cancer and 3,000 healthy people, published in the journal Gut, showed that a much smaller dose of just 75mg could provide significant protection against the disease.
The same dose is sometimes recommended for people recovering from heart attacks and stroke.

Some 18 per cent of healthy people studied said they were taking a low dose of aspirin, or other NSAIDs, at least four times a month, along with 16 per cent of those who had bowel cancer.

While there was no evidence taking NSAIDs influenced the risk of death in bowel cancer patients, it did have a significant protective effect for those who did not have the disease at the start of the trial.

Steve Williamson, Consultant Pharmacist in Cancer at the Royal Pharmaceutical Society, said: “This study adds to the weight of evidence already around that daily low dose aspirin can reduce risk of developing bowel cancer.

"However people must remember that aspirin even at its lowest dose isn’t suitable for everyone, and patients should always talk to their doctor or pharmacist about the potential benefits of taking aspirin.”

Mark Flannagan, chief executive of Beating Bowel Cancer, said: "These findings are encouraging, particularly as, unlike previous studies, this shows that even the lowest daily dose can have an effect on risk reduction after just one year."
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New Microfluidic Chip for Discriminating Bacteria

method for sorting and identifying bacteria has been created by biomedical engineers at Taiwan's National Cheng Kung University. The technique, developed by Hsien-Chang Chang, a professor at the Institute of Biomedical Engineering and the Institute of Nanotechnology and Microsystems Engineering, along with former graduate student I-Fang Cheng and their colleagues, is described in the AIP journal Biomicrofluidics.

Using roughened glass slides patterned with gold electrodes, the researchers created microchannels to sort, trap, and identify bacteria. The technique uses surface enhanced Raman spectroscopy. This type of spectroscopy, says Chang, "is based on the measurement of scattered light from the vibration energy levels of chemical bonds following excitation in a craggy metal surface, which enhances the vibration energy." Different components like proteins or other chemical components on the surface of bacteria become attached to the craggy gold zone; when excited, these components cause representative peaks at different wavelengths, creating spectral "fingerprints."

Although some species of bacteria could show very similar signatures because the components on their surfaces are almost the same, says Chang, bacteria from different genera are distinguishable using the technique.

"In the future, different species of fungi could also be sorted based on their different electrical or physical properties by optimizing conditions such as the flow rate, applied voltage, and frequency," he says. "This portable device could be used for preliminary screening for the pathogenic targets in bacteria-infected blood, urethral irritation, and of raw milk and for food monitoring."sciencedaily

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A sunny outlook for vitamin D detection

Gold nanoparticles aid dectection of vitamin D,
which can be absorbed from the Sun

US researchers have developed a nanotechnology-based test to detect the important vitamin D metabolite calcitriol, the deficiency of which is an indicator of kidney failure.

We all get vitamin D from our diet and from our exposure to sunlight. Vitamin D and its metabolites have an important role in our body's health as they regulate calcium and phosphate levels. Excesses and deficiencies have recently been linked to cardiovascular disease, cancer and kidney disease.

Because of this, clinical demand for an easy test for calcitriol has increased significantly. Most of the current methods use immunoassays that require radio- or enzyme-labels that need large amounts of serum sample and produce radioactive waste and can be very complex which limits their use.

Now Marc Porter and colleagues at the University of Utah in Salt Lake City have developed a test based on using surface enhanced Raman scattering (SERS) combined with gold nanoparticles. This new technique requires a much smaller sample volume and has no radioactive waste. 'Our work demonstrates that a simple optical method, when combined with gold nanoparticle labels, can outperform the standard methods heavily used in clinical diagnostic laboratories around the world,' says Porter.

The combination of SERS with an extrinsic Raman label (ERL), in this case modified gold nanoparticles, has produced a competitive assay with a limit of detection of 8.4 pg/mL - matching the sensitivity of previous immunoassay methods. Following exposure to calcitriol, a biotin-labelled analog can be bound to unoccupied antibody sites allowing subsequent ERL binding to complete the assay and the observed response decreases when the concentration of calcitriol increases.

'This paper is a very nice example of the use of SERS for the detection of metabolites in clinically relevant samples,' comments Karen Faulds, at the Centre of Molecular Nanometrology in Strathclyde, UK. Faulds was impressed with the use of SERS for clinical diagnostics and adds that 'this breakthrough using a SERS based competitive assay holds great promise for the future.'
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