Thursday, March 22, 2012

Research shows how the body senses a range of hot temperatures

Researchers showed that the , or subunits, of heat-sensitive can assemble in many different combinations, yielding new types of channels, each capable of detecting a different temperature. The discovery, in , demonstrates for the first time that only four genes, each encoding one subunit type, can generate dozens of different heat-sensitive channels.

"Researchers in the past have assumed that because there are only four genes, there are only four heat-sensitive channels, but now we have shown that there are many more," said Jie Zheng, leader of the research and an associate professor of physiology and membrane biology at the UC Davis School of Medicine.

The research publishes in the on March 2.

Ion channels are in cell membranes. Their ability to open and close controls the flow of charged , which turns neuron signalling on or off -- in this case to inform the body of the temperature the neuron senses.

The researchers found that when different subunits combine, the resultant hybrid, or heteromeric, channel can detect temperatures about midway between what the "parent" channels detect.

One of the channels they studied, called TRPV1, reacts to hot temperatures -- about 100 degrees Fahrenheit. It is also responsible for the ability to sense spicy foods, such as . A second channel, TRPV3, responds to temperatures of about 85 degrees. It also senses many food flavors such as those found in rosemary, oregano, vanilla and cinnamon that elicit a warm sensation.

When the TRPV1 and TRPV3 subunits recombine, the heteromeric channel is tuned to about 92 degrees. Surprisingly, the study showed that the hybrid channel has an even higher chemical sensitivity than the channels that made it up.

Zheng and his colleagues also showed that channels made up of TRPV1 and TRPV3 subunits react to heat at a rate about midway between that of the two constituent channel subunits. But repeatedly exposing the hybrid channels to their target temperature boosted their response, a behavior called sensitization, which TRPV3 also exhibits.

"It says 'I remember this temperature. I will make a really loud noise to tell the system that it is coming,'" Zheng said. The process allows the body to be more sensitive to temperature.

By contrast, TRPV1 typically responds the same way when repeatedly exposed to its target temperature -- and sometimes even decreases its response, a process called desensitization. It helps the body to adapt to high temperature, Zheng explained.

The research builds on work the team published in 2007 demonstrating that the heat-sensitive subunits can combine to form heteromeric channels. However, at the time, scientists didn't know how these channels respond to heat. The new work shows that the channels are indeed sensitive to different temperatures.

"Knowing that there are many distinct heat-sensing ion channels now opens the way to understand how encode precise temperature information, an important process that allows us to enjoy the rich spectrum of temperature in life -- a memorable warm handshake, a soothing shower and a cup of hot latte -- and add vanilla flavor, please," Zheng said. "It also may provide insights regarding the causes and potential treatments for temperature-sensitivity disorders, such as Raynaud's syndrome."

Raynaud's syndrome is a condition that causes some areas of the body -- such as fingers, toes, the tip of the nose and ears -- to feel numb and cool in response to cold temperatures or stress. The cause is unknown.

The scientists introduced the genes for TRPV1 and TRPV3 channel subunits to cultured human kidney cells. They tagged the genes with fluorescent markers to confirm when the resulting proteins had combined to form a new channel complex.

Once functional channels were formed, the researchers used a glass pipette with a very fine tip to record ion channels' responses to temperature changes.

In order to rapidly increase the , they built an apparatus that allowed them to deliver an infrared laser beam to the cell. The method allowed them to heat the channel more than a thousand times faster than commercially available heating devices.

Provided by University of California - Davis

Scientists save energy by lubricating wood

Scientists at Imperial College London have demonstrated that a key part of biomass processing could be made 80 per cent more energy-efficient by taking advantage of the slippery properties of fluids called ionic solvents. They say this could reduce the cost of biofuels by 3p per litre, around 10% of its current cost.

The efficiency savings can be made during one of the energy-intensive stages of the biomass , when solid timber chunks are turned into a 'soup' of fluids and fine wood particles in an industrial grinder, which works in a similar way to a giant coffee grinder. The discovery paves the way to making the biomass industry greener.

Treating timber with ionic solvents has previously been shown to help processing wood into biofuels and chemicals. While initially this effect was only attributed to the solvents' ability to partially weaken wood's tough, fibrous structure, this new study suggests the are predominantly due to the way that these fluids lubricate the as they go around in the grinder.

Lead author of the study Dr. Agnieszka Brandt, from the Department of Chemistry at Imperial College London, said: "Tree wood is a mine of really valuable chemicals locked up in a safe that we need to unlock before we can use the different components. Breaking down the timber into a fine powder helps us to access these chemicals, but it needs to be an energy-efficient process to make it sustainable. Our previous work showed how the chemical action of ionic solvents improved in the processing, but we were surprised to discover how much more energy could be saved when take advantage of their lubricating physical properties."

'Green' biomass products are often hailed as environmentally friendly alternatives to fossil fuel and its derivatives. Trees such as fast growing species of willow and pine will be an important source of biofuels and basis for manufacturing naturally occurring chemicals like vanillin (a flavoring in the food industry), valuable oils and biomass-derived plastics, such as polystyrenes or polyesters (used for plastic bottles). Scientists are working to ensure biomass lives up to these expectations, assessing and reducing the environmental impact of every part of the product cycle, including the source of its raw materials, how and where they are transported, and what happens to the by-products of the industry.

Research author Tom Welton, Professor of Sustainable Chemistry and Head of Imperial’s Department of Chemistry, said: "Sustainable development has been defined by the UN as development to meet the needs of the present generation without compromising the ability of future generations to meet their own needs.

"The alleviation of poverty and improvement of all of our living standards cannot continue without us also ensuring that our planet is in a condition to support these. As our petrochemical resources run out and we need to turn to other places for our energy and materials needs, we have an opportunity to build these new industries in a sustainable way. This is an opportunity that we can’t afford to miss."

Provided by Imperial College London (news : web)

Benefits of single atoms acting as catalysts in hydrogen-related reactions

Hydrogenation – the addition of to an organic compound – is critical to the food, petrochemical and pharmaceutical industries. Hydrogenation requires the presence of a catalyst, usually a metal or an alloy of both precious and common metals, that allows the hydrogen atoms to bind with other molecules. It is difficult to produce alloys that are selective hydrogenation catalysts, able to attach the hydrogen atoms to specific sites of another molecule.

Tufts chemists and chemical engineers reported that when single atoms of palladium, an expensive precious metal, were added to copper, which is much cheaper and readily available, the resulting "single atom alloy" became active and selective for hydrogenation reactions.

This is the first published research to directly relate the arrangement of individual atoms in a metal alloy to their ability to catalyze hydrogenation reactions, according to E. Charles H. Sykes, associate professor of chemistry at Tufts and senior author on the paper. Sykes focuses much of his research on single molecule chemistry.

Industrial processes typically use small clumps of precious metal five to 10 nanometers wide on supports to make a catalyst. The Tufts scientists scattered single atoms of palladium less than half a nanometer wide onto a copper support. With palladium costing about $650 per ounce, the single atom alloy approach offers big cost savings.

"The we're looking at with smaller amounts of palladium use less energy and yield less chemical byproduct waste, hence they're better for the environment," said Sykes. "These reactions are also more cost-effective because we're working with single atoms of precious metals, which is therefore much cheaper than big clusters of the material. Given that hydrogenation reactions are carried out on a scale of millions of tons per year, there is great potential for this new and less expensive type of catalytic surface."

For this research the Tufts team heated very small amounts of palladium to almost 1,000°C. At that temperature individual atoms evaporated and embedded themselves on the copper surface about three inches away.

A scanning tunneling microscope, which records images of objects at the atomic level, enabled the team to see how these single atoms dispersed in the copper and how molecular hydrogen could then dissociate at individual, isolated palladium sites and spill over onto the copper surface layer.

"This is the first time there has been a definitive microscopic picture of the arrangement of that promote a catalytic hydrogenation reaction. This picture is important because the catalytic hydrogenations that we're studying are vital to many industrial processes," added Sykes. "For example, in petroleum refining, catalytic hydrogenations are performed to make light and hydrogen-rich products like gasoline."

Georgios Kyriakou, research assistant professor of chemistry in the School of Arts and Sciences and first author of the paper; Maria Flytzani-Stephanopoulos, the Robert and Marcy Haber Endowed Professor in Energy Sustainability in the School of Engineering; and a joint Ph.D. student, Matthew Boucher, led testing that determined that the single atom alloy was more effective in catalyzing hydrogenation than denser mixtures of palladium and copper. Mass spectrometry showed that the new alloy catalyzed the hydrogenation of both styrene and with greater than 95% selectivity.

"With the rising cost of precious metals and the increasing scarcity of these metals, learning more about these reactions is encouraging in the search for sustainable global solutions," said Flytzani-Stephanopoulos. "We are looking at how these single-atom alloy catalysts could eventually be used as low-cost alternatives in and dehydrogenation processes for the production of 'green' agricultural chemicals, foods and pharmaceuticals," said Flytzani-Stephanopoulos.

More information: Kyriakou, G., Boucher, M., Jewell, A., Lewis, E., Lawton, T., Baber, A., Tierney, H., Flytzani-Stephanopoulos, M., Sykes, E.C. "Isolated Metal Atom Geometries as a Strategy for Selective Heterogeneous Hydrogenations." Science. Published online and print March 9, 2012. DOI: 10.1126/Science.1215864

Provided by Tufts University

Mobile phone scanner detects harmful bacteria

The scientists published their findings in the latest edition of the journal Analyst.

Outbreaks of E. coli pose a huge threat to health, especially in developing countries. Most strains of E. coli are harmless but some strains however, such as enterohaemorrhagic E. coli (EHEC), can cause severe , according to the . E. coli is transmitted to humans primarily through consumption of contaminated foods, such as raw or undercooked ground , and contaminated raw vegetables and .

As existing detection devices are often expensive and complex, an accurate and efficient detection device could be extremely popular. There are more than five billion mobile phones on the planet and 70 per cent of these are in the

Hongying Zhu and colleagues at the University of California, Los Angeles, developed a device able to take advantage of this technology. Zhu told the RSC's Chemistry World magazine: "Our cell phone based platform would be very useful to bring advanced technologies to remote and resource poor locations" adding that the phone provides "a ubiquitous platform for conducting advanced micro-analysis wherever cell phones work." 

The device consists of glass capillary tubes with light emitting diode (LED) lights on either end. E. coli antibodies are fixed to the sides of the capillaries and trap any E. coli present in a liquid sample. Secondary antibodies and quantum dots are then added to the capillaries and these bind to the trapped E. coli, capturing the bacteria in a sandwich complex. 

The LED lights excite the quantum dots, causing them to emit fluorescent light. The light emission is captured by the phone camera as pictures of the capillaries are taken approximately once a second.   

The team tested the device using water samples and milk and were able to selectively detect low concentrations of E. coli, even in the presence of other bacteria species. Zhu intends to develop the device so one phone could be used to detect different bacteria. 

More information: Quantum dot enabled detection of Escherichia coli using a cell-phone, H Zhu, U Sikora and A Ozcan, Analyst, 2012, DOI: 10.1039/c2an35071h

Provided by Royal Society of Chemistry

The gecko walks on sticky pads

Dancing on the ceiling. Lionel Ritchie's smash hit in the eighties. The song's video clip shows him walking upside down on the ceiling. Just an illusion, of course. , however, can do that, like countless other . Among the bigger animals, the gecko stands out as an example. It can run upside down effortlessly.

can do that because of complex structures on their feet, explains Kamperman. These are bundles of tiny hairs each ending in a sort of little flap. Hundreds of thousands of these little flaps stick to every surface by adhesion and without any other material aid. The work is done by so-called forces. Theoretically speaking, anyway. Kamperman says that it is not exactly clear what the mechanism is.

Not that it matters. Kamperman isn't planning to make gecko feet in exact detail. 'That won't be wise. A gecko foot is a very complex organic system. One should focus on the major issues, get to the essence of the design and copy that. This is what I'm doing now.' And this essence lies in the tiny hairs with the flaps.

Kamperman tries to capture this essence in plastic. She describes her first attempts in the latest issue of Acta Biomaterialia. Kamperman's gecko feet is a little plastic sheet (polydimetylsiloxane) covered with countless tiny rods which resemble studs measuring about ten micrometres in diameter. A gecko would not recognize this, but it works.

To a certain extent, that is. Kampermans' gecko skin sticks well to a base of pure silicon. But hardly any surface is as glassy smooth as that. The wheels fall off when the surface is a little rougher. 'So more is needed than just making tiny rods,' she concludes. Kamperman looks for that something extra in a higher resolution in the material: even more tiny rods. Kamperman now tries to attain that higher resolution by, for example, making rods from so-called block copolymers. These are polymers which take on a certain shape through self-assembly. In this case, it is a helix. The result is a surface densely covered with countless spirals, like a cut-open mattress. Being flexible, the spirals can make firm contact and also let go easily again. Eat your heart out, gecko!

Provided by Wageningen University