Nanotubes Weigh A Single Atom

Nanotubes Weigh A Single Atom

  5:49:00 PM    Science Lover

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How can you weigh a single atom? European researchers have built an exquisite new device that can do just that. It may ultimately allow scientists to study the progress of chemical reactions, molecule by molecule.

A diagram (above) and real-life image (inset) of a carbon nanotube.
(Credit: CARDEQ Project (www.cardeq.eu)

Carbon nanotubes are ultra-thin fibres of carbon and a nanotechnologist’s dream.

They are made from thin sheets of carbon only one atom thick – known as graphene – rolled into a tube only a few nanometres across. Even the thickest is more than a thousand times thinner than a human hair.

Interest in carbon nanotubes blossomed in the 1990s when they were found to possess impressive characteristics that make them very attractive raw materials for nanotechnology of all kinds.

“They have unique properties,” explains Professor Pertti Hakonen of Helsinki University of Technology. “They are about 1000 times stronger than steel and very good thermal conductors and good electrical conductors.”

Hakonen is coordinator of the EU-funded CARDEQ project (http://www.cardeq.eu/) which is exploiting these intriguing materials to build a device sensitive enough to measure the masses of atoms and molecules.

Vibrating strings

A carbon nanotube is essentially an extremely thin, but stiff, piece of string and, like other strings, it can vibrate. As all guitar players know, heavy strings vibrate more slowly than lighter strings, so if a suspended carbon nanotube is allowed to vibrate at its natural frequency, that frequency will fall if atoms or molecules become attached to it.

It sounds simple and the idea is not new. What is new is the delicate sensing system needed to detect the vibration and measure its frequency. Some nanotubes turn out to be semiconductors, depending on how the graphene sheet is wound, and it is these that offer the solution that CARDEQ has developed.

Members of the consortium have taken the approach of building a semiconducting nanotube into a transistor so that the vibration modulates the current passing through it. “The suspended nanotube is, at the same time, the vibrating element and the readout element of the transistor,” Hakonen explains.

“The idea was to run three different detector plans in parallel and then select the best one,” he says. “Now we are down to two. So we have the single electron transfer concept, which is more sensitive, and the field effect transistor concept, which is faster.”

Single atoms

Last November, CARDEQ partners in Barcelona reported that they had sensed the mass of single chromium atoms deposited on a nanotube. But Hakonen says that even smaller atoms, of argon, can now be detected, though the device is not yet stable enough for such sensitivity to be routine. “When the device is operating well, we can see a single argon atom on short time scales. But then if you measure too long the noise becomes large.”

CARDEQ is not alone in employing carbon nanotubes as mass sensors. Similar work is going on at two centres in California – Berkeley and Caltech – though each has adopted a different method to measuring the mass.

All three groups have announced they can perform mass detection on the atomic level using nanotubes, but CARDEQ researchers provided the most convincing data with a clear shift in the resonance frequency.

But a single atom is nowhere near the limit of what is possible. Hakonen is confident they can push the technology to detect the mass of a single nucleon – a proton or neutron.

“It’s a big difference,” he admits, “but typically the improvements in these devices are jump-like. It’s not like developing some well-known device where we have only small improvements from time to time. This is really front-line work and breakthroughs do occur occasionally.”

Biological molecules

If the resolution can be pared down to a single nucleon, then researchers can look forward to accurately weighing different types of molecules and atoms in real time.

It may then become possible to observe the radioactive decay of a single nucleus and to study other types of quantum mechanical phenomena.

But the real excitement would be in tracking chemical and biological reactions involving individual atoms and molecules reacting right there on the vibrating nanotube. That could have applications in molecular biology, allowing scientists to study the basic processes of life in unprecedented detail. Such practical applications are probably ten years away, Hakonen estimates.

“It will depend very much on how the technology for processing carbon nanotubes develops. I cannot predict what will happen, but I think chemical reactions in various systems, such as proteins and so on, will be the main applications in the future.”

The CARDEQ project received funding from the FET-Open strand of the EU’s Sixth Framework Programme for ICT research.

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Capturing Carbon Dioxide In Tiny Bowls: Global Warming Fix From Microbes?

Capturing Carbon Dioxide In Tiny Bowls: Global Warming Fix From Microbes?

  11:27:00 AM    Science Lover

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The accidental discovery of a bowl-shaped molecule that pulls carbon dioxide out of the air suggests exciting new possibilities for dealing with global warming, including genetically engineering microbes to manufacture those CO₂ "catchers," a scientist from Maryland reports.

An unusual bowl-shaped molecule (shown) that pulls carbon dioxide out of the air may provide exciting new possibilities for dealing with global warming, a scientist says. (Credit: The American Chemical Society)

J. A. Tossell notes in the new study that another scientist discovered the molecule while doing research unrelated to global climate change. Carbon dioxide was collecting in the molecule, and the scientist realized that it was coming from air in the lab. Tossell recognized that these qualities might make it useful as an industrial absorbent for removing carbon dioxide.

Tossell's new computer modeling studies found that the molecule might be well-suited for removing carbon dioxide directly from ambient air, in addition to its previously described potential use as an absorbent for CO₂ from electric power plant and other smokestacks. "It is also conceivable that living organisms may be developed which are capable of emplacing structurally ion receptors within their cell membranes," the report notes.

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Spontaneous Assembly: A New Look At How Proteins Assemble And Organize Themselves Into Complex Patterns

Spontaneous Assembly: A New Look At How Proteins Assemble And Organize Themselves Into Complex Patterns

  9:28:00 PM    Science Lover

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Self-assembling and self-organizing systems are the Holy Grails of nanotechnology, but nature has been producing such systems for millions of years. A team of scientists has taken a unique look at how thousands of bacterial membrane proteins are able to assemble into clusters that direct cell movement to select chemicals in their environment. Their results provide valuable insight into how complex periodic patterns in biological systems can be generated and repaired.

PALM is an an ultrahigh-precision visible light microscopy
technique that enables scientists to photo-actively fluoresce
and image individual proteins. This PALM composite of an
E.coli bacterial cell shows the organization of proteins in
the chemotaxis signaling network.
(Credit: Image courtesy of DOE/Lawrence Berkeley National Laboratory)

Researchers with Berkeley Lab, the University of California (UC) Berkeley, the Howard Hughes Medical Institute, and Princeton University, used an ultrahigh-precision visible light microscopy technique called PALM - for Photo-Activated Localization Microscopy - to show that the chemotaxis network of signaling proteins in E.coli bacteria is able to spontaneously form from clusters of proteins without being actively distributed or attached to specific locations in cells. This simple organizational mechanism - dubbed “stochastic self-assembly” - is related to the self-organizing patterns first described in 1952 by the British computer scientist Alan Turing.

“It is not widely appreciated that complex periodic patterns can spontaneously emerge from simple mechanisms, but that is probably what is happening here,” said Jan Liphardt, the biophysicist who led this research.

Liphardt holds a joint appointment with Berkeley Lab’s Physical Biosciences Division and UC Berkeley’s Physics Department. He is the principal author of a paper now available PLoS Biology. Co-authoring the paper with Liphardt were Derek Greenfield, Ann McEvoy, Hari Shroff, Gavin Crooks, Ned Wingreen and Eric Betzig.

Key to a cell’s survival is the manner in which its critical components - proteins, lipids, nucleic acids, etc. - are arranged. For cells to thrive, the organization of these components must be optimized for their respective activities and also reproducible for succeeding generations of cells. Eukaryotic cells feature distinct subcellular structures, such as membrane-bound organelles and protein transport systems, whose complex organization is readily apparent. However, there is also complex spatial organization to be found within prokaryotic cells, such as rod-shaped bacteria like E. coli.

“It has remained somewhat mysterious how bacteria are able to organize and spatially segregate their interiors and membranes,” said Liphardt. “Two cells which are biochemically identical can have very different behaviors, depending upon their spatial organization. With new technologies such as PALM, we are able to see exactly how cells are organized and relate spatial organization with biological function.”

PALM and the Chemotaxis Network

In the PALM technique, target proteins are labeled with tags that fluoresce when activated by weak ultraviolet light. By keeping the intensity of this light sufficiently low, researchers can photoactivate individual proteins.

“Since individual proteins are imaged one at a time, we can localize and count them, and then computationally assemble the locations of all proteins into a composite, high-precision image,” said Liphardt. “With other technologies, we have to choose between observing large clusters or observing single proteins. With PALM, we can examine a cell and see single proteins, protein dimers, and so forth, all the way up to large clusters containing thousands of proteins. This enables us to see the relative organization of individual proteins within clusters and at the same time see how clusters are arranged with respect to one-another.”

Liphardt and his colleagues applied the PALM technique to the E.coli chemotaxis network of signaling proteins, which direct the movement of the bacteria towards or away from sugars, amino acids, and many other soluble molecules in response to environmental cues. The E.coli chemotaxis network is one of the best-understood of all biological signaling systems and is a model for studying bacterial spatial organization because its components display a nonrandom, periodic distribution in the cell membrane.

“Chemotaxis proteins cluster into large sensory complexes that localize to the poles of the bacterial cell,” Liphardt said. “We wanted to understand how these clusters form, what controls their size and density, and how the cellular location of clusters is robustly maintained in growing and dividing cells.”

Using PALM, Liphardt and his colleagues mapped the cellular locations of three proteins central to the chemotaxis signaling network - Tar, CheY and CheW - with a mean precision of 15 nanometers. They found that cluster sizes were distributed with no one size being “characteristic.” For example, a third of the Tar proteins were part of smaller lateral clusters and not of the large polar clusters. Analysis of the relative cellular locations of more than one million individual proteins from 326 cells determined that they are not actively distributed or attached to specific locations in cells, as had been hypothesized.

“Instead,” said Liphardt, “random lateral protein diffusion and protein-protein interactions are probably sufficient to generate the observed complex, ordered patterns. This simple stochastic self-assembly mechanism, which can create and maintain periodic structures in biological membranes without direct cytoskeletal involvement or active transport, may prove to be widespread in both prokaryotic and eukaryotic cells.”

Liphardt and his research group are now applying PALM to signaling complexes in eukaryotic membranes to see how widespread is stochastic self-assembly in nature. Given that biological systems are nature’s version of nanotechnology, the demonstration that stochastic self-assembly is capable of organizing thousands of proteins into complex and reproducible patterns holds promise for a wide range of applications in nanotechnology, including the fabrication of nanodevices and the development of nanoelectronic circuits.

This work was funded by the U.S. Department of Energy’s Office of Science, Energy Biosciences Program, the Sloan and Searle Foundations, and National Institutes of Health grants.

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MP3 Quality Modifier

MP3 Quality Modifier

  8:12:00 PM    Science Lover

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Great sound quality at small file sizes – perfect for your phone!


A lot of mobile phones are getting to be quite capable of playing back audio as well as standalone portable music players. Sony’s Walkman series and Nokia’s XPressMusic series of phones have sold like hot cakes recently.

The problem for a music lover, though, is fitting his entire collection into the small amount of disk space available. A lot of these phones do not support memory cards of more than 4-8GB, with some incapable of reading a card over 2GB. Alternately, a few handsets tend to get quite slow when a lot of data is stored on them.

Of course, managing a lot of music is also difficult on the smaller MP3 players, such as the iPod Shuffle, the Creative Zen Stone, etc. So space management has become an issue for music aficionados.

A great tool to try out is the MP3 Quality Modifier, which promises to take your music files and greatly compress their file sizes with minimal quality loss.

The standalone program – taking just 323KB of disk space itself – opens up to a window with a simple interface. First, you have to use the two buttons in the toolbar to add the MP3 files or a folder that you want to compress.

Once the files are listed in the main pane at the middle (complete with filename, song title, album, artist, bitrate and size), you can select or deselect which ones you want to edit.

Two sections at the bottom determine the kind of compression your file will go through. The ‘Bitrate’ section lets you select the type of mode (variable, constant, average), rate in kbps, and a preset (misspelt as ‘present’, and having four options: high quality, portable, compromise, very low quality). If you don’t know what you are doing when it comes to music editing, using these presets can be very handy.

The ‘Modus’ section gives you the option of figuring out the kind of output (mono, joint stereo, stereo and dual channels) and sample frequency – both of which can be adjusted directly through the preset.

Finally, choose a destination folder to save the newly-edited files to, and you’re done. Hit the ‘Start Process’ in the top toolbar and let the program do the rest. Quick, easy and very handy!

Rating: 3.5/5
Download: www.inspire-soft.net/?nav=soft_mp3qualitymodifier
Direct Download: www.inspire-soft.net/files/MP3QualityModifier1.0.zip
Size: 315.63KB

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