Jan. 10, 2013 — An industrial revolution on a minute scale is taking place in laboratories at The University of Manchester with the development of a highly complex machine that mimics how molecules are made in nature.

Professor Leigh’s molecular machine is based on the ribosome. It features a functionalized nanometre-sized ring that moves along a molecular track, picking up building blocks located on the path and connecting them together in a specific order to synthesize the desired new molecule. First the ring is threaded onto a molecular strand using copper ions to direct the assembly process. Then a “reactive arm” is attached to the rest of the machine and it starts to operate. The ring moves up and down the strand until its path is blocked by a bulky group. The reactive arm then detaches the obstruction from the track and passes it to another site on the machine, regenerating the active site on the arm. The ring is then free to move further along the strand until its path is obstructed by the next building block. This, in turn, is removed and passed to the elongation site on the ring, thus building up a new molecular structure on the ring. Once all the building blocks are removed from the track, the ring de-threads and the synthesis is over. (Credit: Miriam Wilson)

Writing in Nature Materials, the scientists, working with colleagues from Aix-Marseille University, have created a device which potentially can see one molecule though a simple optical system and can analyse its components within minutes. This uses plasmonics -- the study of vibrations of electrons in different materials.

The breakthrough could allow for rapid and more accurate drug testing for professional athletes as it could detect the presence of even trace amounts of a substance.

It could also be used at airports or other high-security locations to prevent would-be terrorists from concealing explosives or traffickers from smuggling drugs. Another possible use could be detecting viruses people might be suffering from.

Graphene, isolated for the first time at The University of Manchester in 2004, has the potential to revolutionise diverse applications from smartphones and ultrafast broadband to drug delivery and computer chips.

It has the potential to replace existing materials, such as silicon, but University of Manchester researchers believe it could truly find its place with new devices and materials yet to be invented.

The researchers, lead by Dr Sasha Grigorenko, suggested a new type of sensing devices: artificial materials with topological darkness. The devices show extremely high response to an attachment of just one relatively small molecule. This high sensitivity relies on topological properties of light phase.

To test their devices, researches covered them with graphene. They then introduced hydrogen onto the graphene, which allowed them to calibrate their devices with far superior sensitivity than with any other material.

Testing for toxins or drugs could be done using a simple blood test, with highly-accurate results in minutes. The researchers found that the sensitivity of their devices is three orders of magnitude better than that of existing models.

The academics, from the School of Physics and Astronomy, hope the research will show the practical applications from an emerging area of research -- singular optics.

Dr Grigorenko said: "The whole idea of this device is to see single molecules, and really see them, under a simple optical system, say a microscope.

"The singular optics which utilise the unusual phase properties of light is a big and emerging field of research, and we have shown how it can have practical applications which could be of great benefit.

"Graphene was one of the best materials we could have used to measure the sensitivity of these molecules. It is so easy to put the hydrogen on to it in controlled way.

"We are only starting to scratch the surface of what this research might tell us but it could have profound implications for drug detection, security and viruses."

Professor Andre Geim and Professor Kostya Novoselov won the Nobel prize for Physics in 2010 for their groundbreaking work on graphene.

source:sciencedaily.

A team of researchers including Peter Ungar, Distinguished Professor of anthropology at the University of Arkansas, reports its findings June 27 in the journal Nature.

Almost 2 million years ago, an elderly female and young male of the species Australopithecus sediba fell into a sinkhole, where their remains were quickly buried in sediment. In 2010, anthropologist Lee Berger of the Institute for Human Evolution at the University of the Witwatersrand in Johannesburg, South Africa, and his colleagues described the remains of this newly characterized creature. Now a team of scientists has studied the teeth of these specimens, which proved to have unique properties because of how the hominins died.

"We have a very unusual type of preservation," Ungar said. "The state of the teeth was pristine." Since the two individuals were buried underground and quickly encased in sediment, parts of the teeth were even preserved with a pocket of air surrounding them. Because of this, the researchers were able to perform dental microwear analyses of the tooth surfaces and high-resolution isotope studies of the tooth enamel on these well-preserved teeth. In addition, because the teeth had not been exposed to the elements since death, they also harbored another thing not discovered before in early hominins -- areas of preserved tartar buildup around the edges of the teeth. In this plaque, the scientists found phytoliths, bodies of silica from plants eaten almost 2 million years ago by these early hominids.

"It's the first time we've been able to look at these three things in one or two specimens," Ungar said.

Using the isotope analysis, the dental microwear analysis and the phytolith analysis, the researchers closed in on the diet of these two individuals, and what they found differs from other early human ancestors from that period. The microwear on the teeth showed more pits and complexity than most other australopiths before it. Like the microwear, the isotopes also showed that the animals were consuming mostly parts of trees, shrubs or herbs rather than grasses.

The phytoliths gave an even clearer picture of what the animals were consuming, including bark, leaves, sedges, grasses, fruit and palm.

"We get a sense of an animal that looked like it was taking advantage of forest resources," Ungar said. This kind of food consumption differs from what had been seen in evidence from other australopiths. "They come out looking like giraffes in terms of their tooth chemistry. A lot of the other creatures there were not eating such forest resources." "These findings tell us a really nice story about these two individuals," Ungar said. "It's fascinating that we found something that went into the mouth of these creatures that was still in the mouth of these creatures."

Ungar conducted the microwear analysis. Amanda Henry of the Max Planck Institute in Leipzig, Germany; Marion Bamford of the University of Witwatersrand; and Lloyd Rossouw of the National Museum Bloemfontein in South Africa conducted the analysis of the phytoliths. Benjamin Passey of Johns Hopkins University; Matt Sponheimer and Paul Sandberg of the University of Colorado at Boulder; and Darryl de Ruiter of Texas A&M conducted the isotope analysis. Lee Berger of the University of Witwatersrand oversaw the project.

ource:sciencedaily.

Jan. 3, 2013 — Plasmonic gold nanoparticles make pinpoint heating on demand possible. Now Rice University researchers have found a way to selectively heat diverse nanoparticles that could advance their use in medicine and industry.

Different types of nanoparticles – in this case, shells, rods and solid spheres – mixed together can be activated individually with pulsed laser light at different wavelengths, according to researchers at Rice University. The tuned particles’ plasmonic response, enhanced by nanobubbles that form at the surface, can be narrowed to a few nanometers under a spectroscope and are easily distinguishable from each other. (Credit: Lapotko Group/Rice University)

Rice scientists led by Dmitri Lapotko and Ekaterina Lukianova-Hleb showed common gold nanoparticles, known since the 19th century as gold colloids, heat up at near-infrared wavelengths as narrow as a few nanometers when hit by very short pulses of laser light. The surprising effect reported in Advanced Materials appears to be related to nonstationary optical excitation of plasmonic nanoparticles. Plasmons are free electrons on the surface of metals that become excited by the input of energy, typically from light. Moving plasmons can transform optical energy into heat.

"The key idea with gold nanoparticles and plasmonics in general is to convert energy," Lapotko said. "There are two aspects to this: One is how efficiently you can convert energy, and here gold nanoparticles are world champions. Their optical absorbance is about a million times higher than any other molecules in nature.

"The second aspect is how precisely one can use laser radiation to make this photothermal conversion happen," he said. Particles traditionally respond to wide spectra of light, and not much of it is in the valuable near-infrared region. Near-infrared light is invisible to water and, more critically for biological applications, to tissue.

"This was the problem," Lapotko said. "All nanoparticles, beginning with solid gold colloids and moving to more sophisticated, engineered gold nanoshells, nanorods, cages and stars, have very wide spectra, typically about 100 nanometers, which means we were allowed to use only one type of nanoparticle at a time. If we tried to use different types, their spectra overlapped and we did not benefit from the high tunability of lasers."

The discovery allows controlled laser pulses to tune the absorbance spectrum of plain gold colloids, Lapotko said. "This novel approach is counter to the established paradigm that assumes optical properties of nanoparticles are pre-set during their fabrication and stay constant during their optical excitation," he said.

The Rice lab showed basic colloidal gold nanoparticles could be efficiently activated by a short laser pulse at 780 nanometers, with an 88-fold amplification of the photothermal effect seen with a continuous laser. The researchers repeated their experiment with nanoparticle clusters in water, in living cancer cells and in animals, with the same or better results: they showed spectral peaks two nanometers wide. Such narrow photothermal spectra had never been seen for metal nanoparticles, either singularly or in clusters.

The effect appears to depend on vapor nanobubbles that form when the particles heat liquid in their immediate environment. The nanobubbles grow and burst in an instant. "Instead of using the nanoparticle as a heat sink with a continuous, stationary laser, we're creating a transient, nonstationary situation in which the particle interacts with the incident laser in a totally different way," Lapotko said. He said the effect is repeatable and works with laser pulses shorter than 100 picoseconds.

Even better, an experiment with mixed nanorods and nanoshells found they responded to laser pulses with strong, distinct signals at wavelengths 10 nanometers apart. That means two or more types of nanoparticles in the same location can be selectively activated on demand.

"The nanoparticles we used were nothing fancy; they were used in the 19th century by Michael Faraday, and it was believed they could do nothing in the near-infrared," he said. "That was the major motivation for people to invent nanorods, nanoshells and the other shapes. Here, we prove these inexpensive particles can behave quite well in near-infrared." He said the discovery opens the possibility that many metal nanoparticles could be used in biomedical and industrial applications where spectral selectivity and tuning would provide "unprecedented" precision.

"This is still more a phenomenon rather than a firmly established mechanism, with a nice theoretical basis," Lapotko said. "But when fully clarified, it could become a universal tool."

Co-authors of the paper are Alexey Volkov, a research scientist at the University of Virginia, and Xiangwei Wu, an associate professor in the Department of Head and Neck Surgery at the University of Texas MD Anderson Cancer Center. Lapotko is a faculty fellow in biochemistry and cell biology, and Lukianova-Hleb is a research scientist at Rice.

The National Institutes of Health supported the research.

Rice scientists led by Dmitri Lapotko and Ekaterina Lukianova-Hleb showed common gold nanoparticles, known since the 19th century as gold colloids, heat up at near-infrared wavelengths as narrow as a few nanometers when hit by very short pulses of laser light. The surprising effect reported in Advanced Materials appears to be related to nonstationary optical excitation of plasmonic nanoparticles. Plasmons are free electrons on the surface of metals that become excited by the input of energy, typically from light. Moving plasmons can transform optical energy into heat.

"The key idea with gold nanoparticles and plasmonics in general is to convert energy," Lapotko said. "There are two aspects to this: One is how efficiently you can convert energy, and here gold nanoparticles are world champions. Their optical absorbance is about a million times higher than any other molecules in nature.

"The second aspect is how precisely one can use laser radiation to make this photothermal conversion happen," he said. Particles traditionally respond to wide spectra of light, and not much of it is in the valuable near-infrared region. Near-infrared light is invisible to water and, more critically for biological applications, to tissue.

"This was the problem," Lapotko said. "All nanoparticles, beginning with solid gold colloids and moving to more sophisticated, engineered gold nanoshells, nanorods, cages and stars, have very wide spectra, typically about 100 nanometers, which means we were allowed to use only one type of nanoparticle at a time. If we tried to use different types, their spectra overlapped and we did not benefit from the high tunability of lasers."

The discovery allows controlled laser pulses to tune the absorbance spectrum of plain gold colloids, Lapotko said. "This novel approach is counter to the established paradigm that assumes optical properties of nanoparticles are pre-set during their fabrication and stay constant during their optical excitation," he said.

The Rice lab showed basic colloidal gold nanoparticles could be efficiently activated by a short laser pulse at 780 nanometers, with an 88-fold amplification of the photothermal effect seen with a continuous laser. The researchers repeated their experiment with nanoparticle clusters in water, in living cancer cells and in animals, with the same or better results: they showed spectral peaks two nanometers wide. Such narrow photothermal spectra had never been seen for metal nanoparticles, either singularly or in clusters.

The effect appears to depend on vapor nanobubbles that form when the particles heat liquid in their immediate environment. The nanobubbles grow and burst in an instant. "Instead of using the nanoparticle as a heat sink with a continuous, stationary laser, we're creating a transient, nonstationary situation in which the particle interacts with the incident laser in a totally different way," Lapotko said. He said the effect is repeatable and works with laser pulses shorter than 100 picoseconds.

Even better, an experiment with mixed nanorods and nanoshells found they responded to laser pulses with strong, distinct signals at wavelengths 10 nanometers apart. That means two or more types of nanoparticles in the same location can be selectively activated on demand.

"The nanoparticles we used were nothing fancy; they were used in the 19th century by Michael Faraday, and it was believed they could do nothing in the near-infrared," he said. "That was the major motivation for people to invent nanorods, nanoshells and the other shapes. Here, we prove these inexpensive particles can behave quite well in near-infrared." He said the discovery opens the possibility that many metal nanoparticles could be used in biomedical and industrial applications where spectral selectivity and tuning would provide "unprecedented" precision.

"This is still more a phenomenon rather than a firmly established mechanism, with a nice theoretical basis," Lapotko said. "But when fully clarified, it could become a universal tool."

Co-authors of the paper are Alexey Volkov, a research scientist at the University of Virginia, and Xiangwei Wu, an associate professor in the Department of Head and Neck Surgery at the University of Texas MD Anderson Cancer Center. Lapotko is a faculty fellow in biochemistry and cell biology, and Lukianova-Hleb is a research scientist at Rice.

The National Institutes of Health supported the research.

source:sciencedaily