E. coli packs a punch - an intestinal insight from ISIS

Commonly found in the intestines of humans and animals, E. coli is normally considered to be a ‘helpful’ bacterium that aids digestion.  However, it can also cause vomiting and diarrhoea, and can be a serious illness for young children, the elderly and those with vulnerable immune systems.  In 2010, 793 incidents of the O157 strain of E. coli were recorded by the Health Protection Agency, but this is thought to only represent a fraction of actual cases because most go unreported.

Discovering how antibacterial proteins attack harmful bacteria is important for establishing new methods of drug delivery. Antibacterial proteins often have to travel across a waterproof cell membrane to reach their target. E. coli bacteria use a similar mechanism when attacking each other so it makes a good comparable study for observing this behaviour.

A bacterial cell is surrounded by a cell membrane that acts as a barrier to hold nutrients and cell components inside, and protect the cell from attack.  The E. coli membrane is particularly difficult to pass through as it is a hydrophobic double layer making it twice as hard for the intruders to penetrate. To penetrate these barriers, E. coli bacteria secrete toxic proteins called Colicins. Just one Colicin can be enough to kill an E. coli bacterium – this is no mean feat as the E. coli bacterium is 400,000 times heavier than the Colicin protein.

For the first time, experiments carried out at ISIS by a team from Newcastle University and funded by the Wellcome Trust have revealed a ‘side view’ of the process that one type of Colicin (Colicin N) uses to kill E. coli bacteria.  The experiments allowed the progress of the Colicin N to be followed as it travelled through the membrane.  More conventional study methods only allow a surface-view of the membrane.  Colicin N specialises in punching a hole through the inner membrane of its target E. coli bacterium. Normally Colicin N would not be able to do this because it is too big to fit through the narrow food-entry pores in the outer membrane of the E. coli.  Results from these experiments have discovered that Colicin hijacks the pore-forming protein Ompf in the outer membrane of the bacteria and then squeezes down the side to reach the inner membrane which it then attacks.

“Neutron scattering techniques were able to show us the insertion of Colicin N into the hydrophobic membrane. Using neutrons allowed us to get a side view of the process, which is important when following proteins across a barrier” said Jeremy Lakey, Professor of Structural Biochemistry at Newcastle University.

Professor Lakey and his team plan to conduct further studies at ISIS to observe later stages of the process.  The results of this research (published in the Journal of Biological Chemistry) will be used to develop new, more effective ways to treat life-threatening illnesses and ultimately help save lives.

Provided by Science and Technology Facilities Council (news : web)

Nano bundles pack a powerful punch: Solid-state energy storage takes a leap forward

Rice University researchers have created a solid-state, nanotube-based supercapacitor that promises to combine the best qualities of high-energy batteries and fast-charging capacitors in a device suitable for extreme environments.

A paper from the Rice lab of chemist Robert Hauge, to be published in the journal Carbon, reported the creation of robust, versatile energy storage that can be deeply integrated into the manufacture of devices. Potential uses span on-chip nanocircuitry to entire power plants.

Standard capacitors that regulate flow or supply quick bursts of power can be discharged and recharged hundreds of thousands of times. Electric double-layer capacitors (EDLCs), generally known as supercapacitors, are hybrids that hold hundreds of times more energy than a standard capacitor, like a battery, while retaining their fast charge/discharge capabilities.

But traditional EDLCs rely on liquid or gel-like electrolytes that can break down in very hot or cold conditions. In Rice's supercapacitor, a solid, nanoscale coat of oxide dielectric material replaces electrolytes entirely.

The researchers also took advantage of scale. The key to high capacitance is giving electrons more surface area to inhabit, and nothing on Earth has more potential for packing a lot of surface area into a small space than carbon nanotubes.

When grown, nanotubes self-assemble into dense, aligned structures that resemble microscopic shag carpets. Even after they're turned into self-contained supercapacitors, each bundle of nanotubes is 500 times longer than it is wide. A tiny chip may contain hundreds of thousands of bundles.

For the new device, the Rice team grew an array of 15-20 nanometer bundles of single-walled carbon nanotubes up to 50 microns long. Hauge, a distinguished faculty fellow in chemistry, led the effort with former Rice graduate students Cary Pint, first author of the paper and now a researcher at Intel, and Nolan Nicholas, now a researcher at Matric.

The array was then transferred to a copper electrode with thin layers of gold and titanium to aid adhesion and electrical stability. The nanotube bundles (the primary electrodes) were doped with sulfuric acid to enhance their conductive properties; then they were covered with thin coats of aluminum oxide (the dielectric layer) and aluminum-doped zinc oxide (the counterelectrode) through a process called atomic layer deposition (ALD). A top electrode of silver paint completed the circuit.

"Essentially, you get this metal/insulator/metal structure," said Pint. "No one's ever done this with such a high-aspect-ratio material and utilizing a process like ALD."

Hauge said the new supercapacitor is stable and scaleable. "All solid-state solutions to energy storage will be intimately integrated into many future devices, including flexible displays, bio-implants, many types of sensors and all electronic applications that benefit from fast charge and discharge rates," he said.

Pint said the supercapacitor holds a charge under high-frequency cycling and can be naturally integrated into materials. He envisioned an electric car body that is a battery, or a microrobot with an onboard, nontoxic power supply that can be injected for therapeutic purposes into a patient's bloodstream.

Pint said it would be ideal for use under the kind of extreme conditions experienced by desert-based solar cells or in satellites, where weight is also a critical factor. "The challenge for the future of energy systems is to integrate things more efficiently. This solid-state architecture is at the cutting edge," he said.

Co-authors of the paper include graduate student Zhengzong Sun; James Tour, the T.T. and W.F. Chao Chair in Chemistry as well as a professor of mechanical engineering and materials science and of computer science, and Howard Schmidt, adjunct assistant professor of chemical and biomolecular engineering, all of Rice; Sheng Xu, a former graduate student at Harvard; and Roy Gordon, the Thomas Dudley Cabot Professor of Chemistry at Harvard University, who developed ALD.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Rice University.

Journal Reference:

Cary L. Pint, Nolan W. Nicholas, Sheng Xu, Zhengzong Sun, James M. Tour, Howard K. Schmidt, Roy G. Gordon, Robert H. Hauge. Three dimensional solid-state supercapacitors from aligned single-walled carbon nanotube array templates. Carbon, 2011; 49 (14): 4890 DOI: 10.1016/j.carbon.2011.07.011

NIST, ASTM land a one-two punch to fight explosives terrorism

 Trace-explosives detectors (TEDs) are an increasingly common sight at airports and on loading docks, and emergency response personnel carry them to evaluate suspicious packages. A new test material developed by the National Institute of Standards and Technology (NIST) in cooperation with ASTM International enables users of these products to evaluate their performance and reliability.

The new testing material, NIST Standard Reference Material (SRM) 2906, Trace Explosives Calibration Solutions, was designed to meet the specifications of ASTM E 2520-07, Standard Practice for Verifying Minimum Acceptable Performance of Trace Explosive Detectors. ASTM is one of the leading industrial organizations for the development of voluntary consensus standards.

The NIST reference material contains calibration solutions of three high explosives: RDX (an ingredient in Composition C-4), PETN, and TNT. Under the test protocol, users sequentially apply a single drop of explosive solution and a solvent blank to swipes, the solvents are allowed to evaporate, and the instrument is tested. A simple ‘yes-no’ alarm checklist is used to determine TED performance.

SRM 2906 includes four ampoules of each of the three explosives and a blank along with a dropper bottle for each. NIST researchers formulated the concentrations of these solutions to be near, but above, the detection limit of commercial swipe-type detectors, which are commonly based on ion mobility spectrometry. When tested with the solutions, properly functioning TEDs should provide an alarm response.

This SRM fully satisfies the need for independent test materials with low uncertainties in concentrations necessary for reliable TED evaluation. Equipment vendors may use the SRM to improve and optimize their designs and demonstrate to their customers how well their machines function. Buyers may use the SRM to make sound procurement decisions. The combination of a validated standard practice and SRM will provide TED users with a reliable means of verifying initial and continuing field performance of their equipment, contributing to the fight against explosives terrorism.

More information: http://www.nist.go … rm/index.cfm

Provided by National Institute of Standards and Technology (news : web)