Thursday, December 19, 2013

New magnetic behaviour in nanoparticles discovered

Schematic representation of the antiferromagnetic coupling
between a magnetic Fe3O4 soft core and a magnetic
Mn3O4 hard shell. The image of an electronic high-resolution
transmission microscope, superimposed on a map of electronic
energy loss spectroscopy (EELS), reveals the high quality of the
interface with a coherent increase between the two phases.
The phenomenon, observed by researchers from the UAB and the ICN2, could lead to important technological applications, such as smaller sized digital memories.

Electronic devices such as mobile phones and tablets spur on a scientific race to find smaller and smaller information processing and storage elements. One of the challenges in this race is to reproduce certain magnetic effects at nanometre scale.

An international collaboration of scientists led by researchers from the Universitat Autònoma de Barcelona Department of Physics and the Institut Catala de Nanociencia i Nanotecnologia, and with the participation of the Universitat de Barcelona, has been able to reproduce in particles measuring 10 to 20 nanometres a magnetic phenomenon of great importance in magnetic devices: the antiferromagnetic coupling between layers.

This phenomenon appears when coupling layers of materials with different magnetic properties, which allows controlling the magnetic behaviour of the whole device. This property has very important technological applications. For example, it forms an important part of data reading systems found in hard drives and in the MRAM memories of computers and mobile devices.

Researchers have managed for the first time to reproduce this phenomenon in nanoscopic materials, measuring a mere few tens of atoms in diameter. They managed to do this by using iron-oxide particles surrounded by a thin layer of manganese-oxide and vice versa: manganese-oxide particles covered by a layer of iron-oxide. The discovery provides an unprecedented control of the magnetic behaviour of nanoparticles, since it permits controlling and easily adjusting their properties without having to manipulate their shape or composition, solely by controlling the temperature and the magnetic fields surrounding it.

“We've been able to reproduce a magnetic behaviour not previously observed in nanoparticles, and this paves the way for miniaturisation up to limits which seemed impossible for magnetic storage and other more sophisticated applications such as spin filters, magnetic codifiers and multi-level recording”, explain Josep Nogués, ICREA research professor, and Maria Dolors Baró, professor of Applied Physics.

The research, published today in Nature Communications, included the participation of professors Maria Dolors Baró and Santiago Suriñach from the Department of Physics of the UAB; ICREA research professor Josep Nogués, from the Department of Physics of the UAB and ICN2; researchers from the Department of Inorganic Chemistry and from the Department of Electronics at the University of Barcelona (UB); researchers from the Complutense University of Madrid; the Università degli Studi di Firenze, Italy; the St. Petersburg Nuclear Physics Institute, Russia; the Stockholm University, Sweden; the NCSR in Greece; the Oak Ridge National Laboratory, USA; the Miami University, Ohio, USA; and the Argonne National Laboratory, USA.


Source: http://www.uab.es/servlet/Satellite/latest-news/news-detail/new-magnetic-behaviour-in-nanoparticles-discovered-1096476786473.html?noticiaid=1345665021035

Liquid Crystal 'Flowers' That Can Be Used as Lenses

A team of material scientists, chemical engineers and physicists from the University of Pennsylvania has made another advance in their effort to use liquid crystals as a medium for assembling structures.
In their earlier studies, the team produced patterns of “defects,” useful disruptions in the repeating patterns found in liquid crystals, in nanoscale grids and rings. The new study adds a more complex pattern out of an even simpler template: a three-dimensional array in the shape of a flower.      
And because the petals of this “flower” are made of transparent liquid crystal and radiate out in a circle from a central point, the ensemble resembles a compound eye and can thus be used as a lens.  
The team consists of Randall Kamien, professor in the School of Arts and Sciences’ Department of Physics and Astronomy; Kathleen Stebe, the School of Engineering and Applied Science’s deputy dean for research and professor in Chemical and Biomolecular Engineering and Shu Yang, professor in Engineering’s departments of Materials Science and Engineering and Chemical and Biomolecular Engineering. Members of their labs also contributed to the new study, including lead author Daniel Beller, Mohamed Gharbi and Apiradee Honglawan.    
Their work was published in Physical Review X.   
The researchers’ ongoing work with liquid crystals is an example of a growing field of nanotechnology known as “directed assembly,” in which scientists and engineers aim to manufacture structures on the smallest scales without having to individually manipulate each component. Rather, they set out precisely defined starting conditions and let the physics and chemistry that govern those components do the rest.  
The starting conditions in the researchers previous experiments were templates consisting of tiny posts. In one of their studies, they showed that changing the size, shape or spacing of these posts would result in corresponding changes in the patterns of defects on the surface of the liquid crystal resting on top of them. In another experiment, they showed they could make a “hula hoop” of defects around individual posts, which would then act as a second template for a ring of defects at the surface.
In their latest work, the researchers used a much simpler cue.    
“Before we were growing these liquid crystals on something like a trellis, a template with precisely ordered features,” Kamien said. “Here, we’re just planting a seed.”
The seed, in this case, were silica beads — essentially, polished grains of sand. Planted at the top of a pool of liquid crystal flower-like patterns of defects grow around each bead.
The key difference between the template in this experiment and ones in the research team’s earlier work was the shape of the interface between the template and the liquid crystal.
In their experiment that generated grid patterns of defects, those patterns stemmed from cues generated by the templates’ microposts. Domains of elastic energy originated on the flat tops and edges of these posts and travelled up the liquid crystal’s layers, culminating in defects. Using a bead instead of a post, as the researchers did in their latest experiment, makes it so that the interface is no longer flat.             
“Not only is the interface at an angle, it’s an angle that keeps changing,” Kamien said. “The way the liquid crystal responds to that is that it makes these petal-like shapes at smaller and smaller sizes, trying to match the angle of the bead until everything is flat.”
Surface tension on the bead also makes it so these petals are arranged in a tiered, convex fashion. And because the liquid crystal can interact with light, the entire assembly can function as a lens, focusing light to a point underneath the bead.
“It’s like an insect’s compound eye, or the mirrors on the biggest telescopes,” said Kamien. “As we learn more about these systems, we’re going to be able to make these kinds of lenses to order and use them to direct light.”
This type of directed assembly could be useful in making optical switches and in other applications.
The research was supported by the National Science Foundation, Penn’s Materials Science Research and Engineering Center and the Simons Foundation.

Wednesday, December 18, 2013

New method for the mass production of boron/nitrogen co-doped graphene nanoplatelets

This is a schematic representation for the formation of BCN-graphene via solvothermal reaction between carbon tetrachloride (CCl4) boron tribromide (BBr3) and nitrogen (N2) in the presence of potassium (K). Photograph is of the autoclave after the reaction, showing the formation of BCN-graphene (black) and potassium halide (KCl and KBr, white).

Image: UNIST



Ulsan National Institute of Science and Technology (UNIST) announced a method for the mass production of boron/nitrogen co-doped graphene nanoplatelets, which led to the fabrication of a graphene-based field-effect transistor (FET) with semiconducting nature. This opens up opportunities for practical use in electronic devices.

The Ulsan National Institute of Science and Technology (UNIST) research team led by Prof. Jong-Beom Baek have discovered an efficient method for the mass production of boron/nitrogen co-doped graphene nanoplatelets (BCN-graphene) via a simple solvothermal reaction of BBr3/CCl4/N2 in the presence of potassium. This work was published in "Angewandte Chemie International Edition" as a VIP ("Very Important Paper".

Since graphene was experimentally discovered in 2004, it has been the focus of vigorous applied research due to its outstanding properties such as high specific surface area, good thermal and electrical conductivities, and many more properties.

However, its Achilles heel is a vanishing band-gap for semiconductor application. As a result, it is not suitable for logic applications, because devices cannot be switched off. Therefore, graphene must be modified to produce a band-gap, if it is to be used in electronic devices.

Various methods of making graphene-based field effect transistors (FETs) have been exploited, including doping graphene, tailoring graphene-like a nanoribbon, and using boron nitride as a support. Among the methods of controlling the band-gap of graphene, doping methods show the most promisinge in terms of industrial scale feasibility.

Although world leading researchers have tried to add boron into graphitic framework to open its band-gap for semiconductor applications, there has not been any notable success yet. Since the atomic size of boron (85 pm) is larger than that of carbon (77 pm), it is difficult to accommodate boron into the graphitic network structure.

A new synthetic protocol developed by a research team from UNIST, a leading Korean university, has revealed that boron/nitrogen co-doping is only feasible when carbon tetrachloride (CCl4 ) is treated with boron tribromide (BBr3 ) and nitrogen (N2) gas.

In order to help boron-doping into graphene structure, the research team used nitrogen (70 pm), which is a bit smaller than carbon and boron. The idea was very simple, but the result was surprising. Pairing two nitrogen atoms and two boron atoms can compensate for the atomic size mismatch. Thus, boron and nitrogen pairs can be easily introduced into the graphitic network. The resultant BCN-graphene generates a band-gap for FETs.

"Although the performance of the FET is not in the ranges of commercial silicon-based semiconductors, this initiative work should be the proof of a new concept and a great leap forward for studying graphene with band-gap opening," said Prof. Jong-Beom Baek.

"I believe this work is one of the biggest advancements in considering the viability of a simple synthetic approach," said Ph.D. candidate Sun-Min Jung, the first author of this article.

Prof. Baek explains the next step: "Now, the remaining challenge is fine-tuning a band-gap to improve the on/off current ratio for real device applications."

 
Information about the research

Other researchers in the team include Profs. Joon Hak Oh, Noejung Park, HuYoung Jeong and 6 graduate students.

The research work was funded by the National Research Foundation (NRF) of Korea, and the US Air Force Office of Scientific Research through the Asian Office of Aerospace R&D (AFOSR-AOARD).


Homepage of Jong-Beom Baek : http://jbbaek.unist.ac.kr


Cells from the eye are inkjet printed for the first time

Close-up of retinal cells in a jet
IOP Publising, Biofabrication
A group of researchers from the UK have used inkjet printing technology to successfully print cells taken from the eye for the very first time.

The breakthrough, which has been detailed in a paper published today, 18 December, in IOP Publishing’s journal Biofabrication, could lead to the production of artificial tissue grafts made from the variety of cells found in the human retina and may aid in the search to cure blindness.
At the moment the results are preliminary and provide proof-of-principle that an inkjet printer can be used to print two types of cells from the retina of adult rats―ganglion cells and glial cells. This is the first time the technology has been used successfully to print mature central nervous system cells and the results showed that printed cells remained healthy and retained their ability to survive and grow in culture.
Co-authors of the study Professor Keith Martin and Dr Barbara Lorber, from the John van Geest Centre for Brain Repair, University of Cambridge, said: “The loss of nerve cells in the retina is a feature of many blinding eye diseases. The retina is an exquisitely organised structure where the precise arrangement of cells in relation to one another is critical for effective visual function”.
“Our study has shown, for the first time, that cells derived from the mature central nervous system, the eye, can be printed using a piezoelectric inkjet printer. Although our results are preliminary and much more work is still required, the aim is to develop this technology for use in retinal repair in the future.”
Printed glia cells
IOP Publising,
Biofabrication

The ability to arrange cells into highly defined patterns and structures has recently elevated the use of 3D printing in the biomedical sciences to create cell-based structures for use in regenerative medicine.
In their study, the researchers used a piezoelectric inkjet printer device that ejected the cells through a sub-millimetre diameter nozzle when a specific electrical pulse was applied. They also used high speed video technology to record the printing process with high resolution and optimised their procedures accordingly.
“In order for a fluid to print well from an inkjet print head, its properties, such as viscosity and surface tension, need to conform to a fairly narrow range of values. Adding cells to the fluid complicates its properties significantly,” commented Dr Wen-Kai Hsiao, another member of the team based at the Inkjet Research Centre in Cambridge.
Once printed, a number of tests were performed on each type of cell to see how many of the cells survived the process and how it affected their ability to survive and grow.
The cells derived from the retina of the rats were retinal ganglion cells, which transmit information from the eye to certain parts of the brain, and glial cells, which provide support and protection for neurons.
“We plan to extend this study to print other cells of the retina and to investigate if light-sensitive photoreceptors can be successfully printed using inkjet technology. In addition, we would like to further develop our printing process to be suitable for commercial, multi-nozzle print heads,” Professor Martin concluded.
The research was undertaken by Dr. Barbara Lorber, also at the John van Geest Centre for Brain Repair, in collaboration with Dr. Wen-Kai Hsiao and Prof. Ian Hutchings from the Inkjet Research Centre, University of Cambridge. The work was funded by Fight for Sight, the van Geest Foundation and the EPSRC.
From Wednesday 18 December, the paper can be downloaded fromhttp://iopscience.iop.org/1758-5090/6/1/015001/article

Mysteries of the Unseen World


Ready to Go

Photograph courtesy Riccardo Antonelli, Pisa University, Pisa, Italy
Winner: The Natural World — August/September
The pollen spores of a cutleaf geranium (Geranium dissectum) jut out, as if eager to fulfill their mission.
Image Details
Instrument used: Quanta SEM Family
Magnification: 500x
Horizontal Field Width: 298 μm
Vacuum: Low vacuum
Voltage: 12.50 kV
Spot: 4.0
Working Distance: 5.1 mm
Detector: LFD (Low vacuum)


FEI is a world leader in the production of electron microscopes (think: seeing things at the nano-scale) and is partnering with Nat Geo Entertainment on the upcoming film, Mysteries of the Unseen World

Every year FEI holds a photo contest to find out what folks in the field are doing with their amazing microscopes, and to give scientists and researchers the chance to share their exploration of the sub-microscopic world. The winners of the 2012 FEI Image Contest are below. These are the best images from four categories: Around the House, The Natural World, The Human Body, and Other Relevant Science. 

Check out the photos first and see if you can guess what you are seeing, then look at the caption to find out what you are really seeing! A whole new world is open to us thanks to FEI and other cutting-edge technology creators, as you will see in Mysteries of the Unseen World.

Algae to crude oil: Million-year natural process takes minutes in the lab

Process simplifies transformation of algae to oil, water and usable byproducts

Engineers have created a continuous chemical process that produces useful crude oil minutes after they pour in harvested algae — a verdant green paste with the consistency of pea soup.
The research by engineers at the Department of Energy's Pacific Northwest National Laboratory was reported recently in the journalAlgal Research. A biofuels company, Utah-based Genifuel Corp., has licensed the technology and is working with an industrial partner to build a pilot plant using the technology.
In the PNNL process, a slurry of wet algae is pumped into the front end of a chemical reactor. Once the system is up and running, out comes crude oil in less than an hour, along with water and a byproduct stream of material containing phosphorus that can be recycled to grow more algae.
With additional conventional refining, the crude algae oil is converted into aviation fuel, gasoline or diesel fuel. And the waste water is processed further, yielding burnable gas and substances like potassium and nitrogen, which, along with the cleansed water, can also be recycled to grow more algae.
While algae has long been considered a potential source of biofuel, and several companies have produced algae-based fuels on a research scale, the fuel is projected to be expensive. The PNNL technology harnesses algae's energy potential efficiently and incorporates a number of methods to reduce the cost of producing algae fuel.
"Cost is the big roadblock for algae-based fuel," said Douglas Elliott, the laboratory fellow who led the PNNL team's research. "We believe that the process we've created will help make algae biofuels much more economical."
PNNL scientists and engineers simplified the production of crude oil from algae by combining several chemical steps into one continuous process. The most important cost-saving step is that the process works with wet algae. Most current processes require the algae to be dried — a process that takes a lot of energy and is expensive. The new process works with an algae slurry that contains as much as 80 to 90 percent water.
"Not having to dry the algae is a big win in this process; that cuts the cost a great deal," said Elliott. "Then there are bonuses, like being able to extract usable gas from the water and then recycle the remaining water and nutrients to help grow more algae, which further reduces costs."
While a few other groups have tested similar processes to create biofuel from wet algae, most of that work is done one batch at a time. The PNNL system runs continuously, processing about 1.5 liters of algae slurry in the research reactor per hour. While that doesn't seem like much, it's much closer to the type of continuous system required for large-scale commercial production.
The PNNL system also eliminates another step required in today's most common algae-processing method: the need for complex processing with solvents like hexane to extract the energy-rich oils from the rest of the algae. Instead, the PNNL team works with the whole algae, subjecting it to very hot water under high pressure to tear apart the substance, converting most of the biomass into liquid and gas fuels.
The system runs at around 350 degrees Celsius (662 degrees Fahrenheit) at a pressure of around 3,000 PSI, combining processes known as hydrothermal liquefaction and catalytic hydrothermal gasification. Elliott says such a high-pressure system is not easy or cheap to build, which is one drawback to the technology, though the cost savings on the back end more than makes up for the investment.
"It's a bit like using a pressure cooker, only the pressures and temperatures we use are much higher," said Elliott. "In a sense, we are duplicating the process in the Earth that converted algae into oil over the course of millions of years. We're just doing it much, much faster."
The products of the process are:
  • Crude oil, which can be converted to aviation fuel, gasoline or diesel fuel. In the team's experiments, generally more than 50 percent of the algae's carbon is converted to energy in crude oil — sometimes as much as 70 percent.
  • Clean water, which can be re-used to grow more algae.
  • Fuel gas, which can be burned to make electricity or cleaned to make natural gas for vehicle fuel in the form of compressed natural gas.
  • Nutrients such as nitrogen, phosphorus, and potassium — the key nutrients for growing algae.
Elliott has worked on hydrothermal technology for nearly 40 years, applying it to a variety of substances, including wood chips and other substances. Because of the mix of earthy materials in his laboratory, and the constant chemical processing, he jokes that his laboratory sometimes smells "like a mix of dirty socks, rotten eggs and wood smoke" — an accurate assessment.
Genifuel Corp. has worked closely with Elliott's team since 2008, licensing the technology and working initially with PNNL through DOE's Technology Assistance Program to assess the technology.
"This has really been a fruitful collaboration for both Genifuel and PNNL," said James Oyler, president of Genifuel. "The hydrothermal liquefaction process that PNNL developed for biomass makes the conversion of algae to biofuel much more economical. Genifuel has been a partner to improve the technology and make it feasible for use in a commercial system.
"It's a formidable challenge, to make a biofuel that is cost-competitive with established petroleum-based fuels," Oyler added. "This is a huge step in the right direction."
The recent work is part of DOE's National Alliance for Advanced Biofuels & Bioproducts, or NAABB. This project was funded with American Recovery and Reinvestment Act funds by DOE's Office of Energy Efficiency and Renewable Energy. Both PNNL and Genifuel have been partners in the NAABB program.
In addition to Elliott, authors of the paper include Todd R. Hart, Andrew J. Schmidt, Gary G. Neuenschwander, Leslie J. Rotness, Mariefel V. Olarte, Alan H. Zacher, Karl O. Albrecht, Richard T. Hallen and Johnathan E. Holladay, all at PNNL.
Reference: Douglas C. Elliott, Todd R. Hart, Andrew J. Schmidt, Gary G. Neuenschwander, Leslie J. Rotness, Mariefel V. Olarte, Alan H. Zacher, Karl O. Albrecht, Richard T. Hallen and Johnathan E. Holladay, Process development for hydrothermal liquefaction of algae feedstocks in a continuous-flow reactor, Algal Research, Sept. 29, 2013, DOI: 10.1016/j.algal.2013.08.005.

Tuesday, December 17, 2013

Duke engineers make strides toward artificial cartilage

Composite material closest yet to properties of the real thing


A Duke research team has developed a better recipe for synthetic replacement cartilage in joints.

Combining two innovative technologies they each helped develop, lead authors Farshid Guilak, a professor of orthopedic surgery and biomedical engineering, and Xuanhe Zhao, assistant professor of mechanical engineering and materials science, found a way to create artificial replacement tissue that mimics both the strength and suppleness of native cartilage. Their results appear Dec. 17 in the journal Advanced Functional Materials.


Tiny interwoven fibers make up the three-dimensional 
fabric "scaffold" into which a strong, pliable hydrogel is 
integrated and injected with stem cells, forming a 
framework for growing cartilage. This image appears 
on the cover of the Dec. 17, 2013, issue of Advanced 
Functional Materials.
Credit: courtesy of Frank Moutos and Farshid Guilak
Articular cartilage is the tissue on the ends of bones where they meet at joints in the body – including in the knees, shoulders and hips. It can erode over time or be damaged by injury or overuse, causing pain and lack of mobility. While replacing the tissue could bring relief to millions, replicating the properties of native cartilage -- which is strong and load-bearing, yet smooth and cushiony -- has proven a challenge.

In 2007 Guilak and his team developed a three-dimensional fabric "scaffold" into which stem cells could be injected and successfully "grown" into articular cartilage tissue. Constructed of minuscule woven fibers, each of the scaffold's seven layers is about as thick as a human hair. The finished product is about 1 millimeter thick.

Since then, the challenge has been to develop the right medium to fill the empty spaces of the scaffold -- one that can sustain compressive loads, provide a lubricating surface and potentially support the growth of stem cells on the scaffold. Materials supple enough to simulate native cartilage have been too squishy and fragile to grow in a joint and withstand loading. "Think Jell-O," says Guilak. Stronger substances, on the other hand, haven't been smooth and flexible enough.

That's where the partnership with Zhao comes in.


 This is a closer look at the scaffolding integrated with Xuanhe Zhao's hydrogel. The composite material, formed through a process comparable to pouring concrete over a steel framework, may be a serviceable synthetic replacement for the load-bearing cartilage found between bones.
Credit: courtesy of I-Chien Liao, Frank Moutos, Brad Estes
Zhao proposed a theory for the design of durable hydrogels (water-based polymer gels) and in 2012 collaborated with a team from Harvard University to develop an exceptionally strong yet pliable interpenetrating-network hydrogel.
"It's extremely tough, flexible and formable, yet highly lubricating," Zhao says. "It has all the mechanical properties of native cartilage and can withstand wear and tear without fracturing."

He and Guilak began working together to integrate the hydrogel into the fabric of the 3-D woven scaffolds in a process Zhao compares to pouring concrete over a steel framework.

In their experiments, the researchers compared the resulting composite material to other combinations of Guilak's scaffolding embedded with previously studied hydrogels. The tests showed that Zhao's invention was tougher than the competition with a lower coefficient of friction. And though the resulting material did not quite meet the standards of natural cartilage, it easily outperformed all other known potential artificial replacements across the board, including the hydrogel and scaffolding by themselves.

"From a mechanical standpoint, this technology remedies the issues that other types of synthetic cartilage have had," says Zhao, founder of Duke's Soft Active Materials (SAMs) Laboratory. "It's a very promising candidate for artificial cartilage in the future."
The team's next step will likely be to implant small patches of the synthetic cartilage in animal models, according to Guilak and Zhao.

Their work was supported in part by National Institutes of Health grants AG15768, AR50245, AR48182, AR48852, the Arthritis Foundation, the Collaborative Research Center, AO Foundation, Davos, Switzerland and the NSF (CMMI-1253495, CMMI-1200515, and DMR-1121107).

"Composite Three-Dimensional Woven Scaffolds with Interpenetrating Network Hydrogels to Create Functional Synthetic Articular Cartilage," Liao, I.-C., Moutos, F. T., Estes, B. T., Zhao, X. and Guilak, F. Adv. Funct. Mater., 2013. doi: 10.1002/adfm.201300483

Source: http://today.duke.edu/2013/12/artcart

"Nanobiopsy" allows scientists to operate on living cells

Scientists have developed a device that can take a "biopsy" of a living cell, sampling minute volumes of its contents without killing it.
Much research on molecular biology is carried out on populations of cells, giving an average result that ignores the fact that every cell is different. Techniques for studying single cells usually destroy them, making it impossible to look at changes over time.
The new tool, called a nanobiopsy, uses a robotic glass nanopipette to pierce the cell membrane and extract a volume of around 50 femtolitres – 0.00000000000005 litres, around one per cent of the cell’s contents.
It will allow scientists to take samples repeatedly, to study the progression of disease at a molecular level in an individual cell. It can also be used to deliver material into cells, opening up ways to reprogram diseased cells.
“This is like doing surgery on individual cells,” said Dr Paolo Actis, from the Department of Medicine at Imperial College London, who developed the technology with colleagues at the University of California, Santa Cruz.
“This technology will be extremely useful for research in many areas. You could use it to dynamically study how cancer cells are different from healthy cells, or look at how brain cells are affected by Alzheimer’s disease. The possibilities are immense.”
To get inside the cell, the nanopipette is plunged downwards about one micrometre to pierce the cell membrane. Applying a voltage across the tip makes fluid flow into the pipette. When the pipette is removed from the cell, the membrane remains intact and the cell retains its shape.
The device is based on a scanning ion conductance microscope, which uses a robotic nanopipette, about 100 nanometres in diameter, to scan the surface of cells. The nanopipette is filled with an electrolyte solution and the ion current is measured inside the tip. When the pipette gets close to a cell membrane, the ion current decreases. This measurement is used to guide the tip across the surface of a sample at a constant distance, producing a picture of the surface.
In an initial study published in the journal ACS Nano, the researchers used the nanobiopsy technique to extract and sequence messenger RNA, molecules carrying genetic code transcribed from DNA in the cell’s nucleus. This allowed them to see which genes were being expressed in the cell.
They were also able to extract whole mitochondria – the power units of the cell. Mitochondria contain their own DNA, and the researchers discovered that the genomes of different mitochondria in the same cell are different.
They are now working on adapting the technology to incorporate sensors on the pipette tip that can instantly measure different molecules.
The research was funded by the US National Cancer Institute and National Institutes of Health.

Alzheimer-substance may be the nanomaterial of tomorrow

It causes brain diseases like Alzheimer’s, Parkinson’s and Creutzfeldt-Jakob’s disease. It is also hard and rigid as steel. Now research at Chalmers University of Technology shows that the amyloid protein carries unique characteristics that may lead to the development of new composite materials for nano processors and data storage of tomorrow and even make objects invisible.

Piotr Hanczyc, PhD student at the department of Chemical and Biological Engineering, shows in an article in Nature Photonics, that the amyloid, a very dense aggregate of protein that causes brain diseases like Alzheimer's and Parkinson's, carries unique characteristics. Unlike well-functioning protein the amyloid reacts upon multi photon laser irradiation. This laser may in the future possibly be used for detection of amyloids inside a human brain. This discovery is in itself a breakthrough.

- But you can also create these aggregates in an artificial way in a laboratory and in combination with other materials create unique characteristics, Piotr Hanczyc says.

The amyloid aggregates are as hard and rigid as steel. The difference is that steel is much heavier and has defined material properties whereas amyloids can be tuned for desired purpose. By attaching a material’s molecules to the dense amyloid its characteristics change. This has been known for more than ten years and is already used by scientists.

- What hasn’t been known is that the amyloids react to multi-photon irradiation and this opens up new possibilities to also change the nature of the material attached to the amyloids, Piotr Hanczyc says.

The amyloids are shaped like discs densely piled upon each other.  When a material gets merged with these discs its molecules end up so densely and regularly that they can communicate and exchange information. This means totally new possibilities to change a material’s characteristics. 

Multi-photon tests on materials tied to amyloids are yet to be performed, but Piotr sees an opportunity for cooperation with Chalmers material science researchers interested for example in solar cell technology. 

And though it may still be science fiction, he also considers that one day scientists may use the material properties of amyloid fibrils in the research of invisible metamaterials.

- An object’s ability to reflect light could be altered so that what’s behind it gets reflected instead of the object itself, in principle changing the index of light refraction, kind of like when light hits the surface of water, Piotr Hanczyc says. 

Nanoparticles and their orbital positions

Physicists have developed a “planet-satellite model” to precisely connect and arrange nanoparticles in three-dimensional structures. Inspired by the photosystems of plants and algae, these artificial nanoassemblies might in the future serve to collect and convert energy.

If the scientists‘ nanoparticles were a million times larger, the laboratory would look like an arts and crafts room at Christmas time: gold, silver and colorful shiny spheres in different sizes and filaments in various lengths. For at the center of the nanoscale “planet-satellite model” there is a gold particle which is orbited by other nanoparticles made of silver, cadmium selenide or organic dyes.
As if by magic, cleverly designed DNA strands connect the satellites with the central planet in a very precise manner. The technique behind this, called “DNA origami”, is a specialty of physics professor Tim Liedl (LMU Munich) and his team. Together with the group of Professor Jochen Feldmann (also LMU Munich) they introduced and analyzed this novel assembly scheme. Both groups are part of the cluster of excellence Nanosystems Initiative Munich (NIM).
Large or small, near or far
A distinctive feature of the new method is the modular assembly system which allows the scientists to modify all aspects of the structure very easily and in a controlled manner: the size of the central nanoparticle, the types and sizes of the “satellites” and the distance between planet and satellite particle. The approach also enables the physicists to adapt and optimize their system for other purposes.
Photonic systems
Metals, semiconductors or fluorescent organic molecules serve as satellites. Thus, like the antenna molecules in natural photosystems, such satellite elements might in future be organized to collect light energy and transfer it to a catalytic reaction center where it is converted into another form of energy. For the time being, however, the model allows the scientists to investigate basic physical effects such as the so-called quenching process, which refers to the changing fluorescence intensity of a dye molecule as a function of the distance to the central gold nanoparticle.
“The modular assembly principle and the high yield we obtained in the production of the planet-satellite systems were the crucial factors for reliably investigating this well-known effect with the new methods,” explains Robert Schreiber, lead author of the study.
A whole new cosmos
In addition, the scientists succeeded in joining individual planet-satellite units together into larger arrays, while maintaining the combinatorial freedom. This way, it might be possible to develop complex and functional three-dimensional nanosystems, which could be used as Raman spectroscopy platforms, as plasmonic energy funnels or as nanoporous materials for catalytic applications.

Ultrafast heating of water - This pot boils faster than you can watch it

A single terahertz flash can heat the water cloud to
600 degrees centigrade, while leaving all water
molecules intact. Credit: Oriol Vendrell/DESY 


Novel method opens new paths for experiments with heated samples of biological relevance

Scientists from the Hamburg Center for Free-Electron Laser Science have devised a novel way to boil water in less than a trillionth of a second. The theoretical concept, which has not yet been demonstrated in practice, could heat a small amount of water by as much as 600 degrees Celsius in just half a picosecond (a trillionth of a second). 

That is much less than the proverbial blink of an eye: one picosecond is to a second what one second is to almost 32 millennia. 

This would make the technique the fastest water-heating method on earth.
The novel concept opens up interesting new ways for experiments with heated samples of chemical or biological relevance, as the inventors report in this week's issue of the scientific journal Angewandte Chemie - International Edition (Nr. 51, 16 December). "Water is the single most important medium in which chemical and biological processes take place," explains DESY scientist Dr. Oriol Vendrell from the Center for Free-Electron Laser Science CFEL, a cooperation of DESY, the University of Hamburg and the German Max Planck Society. "Water is not just a passive solvent, but plays an important role in the dynamics of biological and chemical processes by stabilising certain chemical compounds and enabling specific reactions."

All it takes for superfast water heating is a concentrated flash of terahertz radiation. Terahertz radiation consists of electromagnetic waves with a frequency between radio waves and infrared. Terahertz flashes can be generated with devices called free-electron lasers that send accelerated electrons on a well defined slalom course. The particles emit electromagnetic waves in each bend that add up to an intense laser like pulse. The terahertz pulse changes the strength of the interaction between water molecules in a very short time, which immediately start to vibrate violently.

The scientists calculated the interaction of the terahertz flash with bulk water. The simulations were performed at the Supercomputer Center Jülich and used a total of 200,000 hours of processor time by massively parallel computing. On a single processor machine this would correspond to about 20 years of computation. "We have calculated that it should be possible to heat up the liquid to about 600 degrees Celsius within just half a picosecond, obtaining a transiently hot and structureless environment still at the density of the liquid, leaving all water molecules intact," explains Vendrell.

The novel method can only heat about one nanolitre (billionth of a litre) in one go. This may sound small, but is large enough for most experiments. For comparison, ink-jet printers fire droplets that are as small as one picolitre, which is a thousand times less than a nanolitre.

"The idea is to heat-up the 'solvent' so that many molecules start the desired chemical process at the same time and then watch the reaction evolve," explains Vendrell, who worked out the super heater with co-authors Pankaj Kr. Mishra and Prof. Robin Santra, also of CFEL. Although the hot mini-cloud will fly apart in less than a millisecond (a thousandth of a second), it lasts long enough to unravel everything of interest in thermal reactions such as the combination of small organic molecules to form new substances. The team currently investigates how the intense pulse of terahertz radiation affects different types of molecules dissolved in water, from inorganic to biological systems.

The reaction progress can be probed with ultrashort X-ray flashes like they will be produced by the 3.4-kilometre-long X-ray free-electron laser European XFEL, which currently is being built between the DESY campus in Hamburg and the neighbouring town of Schenefeld. When completed, the European XFEL will be able to generate 27,000 intense X-ray laser flashes per second, which can for example be used to record the different stages of chemical reactions.

One advantage of the heating method is that the terahertz pulse can be very well synchronised with the X-ray flashes to start the experiment and then probe the reaction after a well defined time. "The transient and hot environment achieved by the terahertz pulse could have interesting properties, like a matrix to study activated chemical processes," says Vendrell. "This will be the subject of further investigations."

Virus grows tube to insert DNA during infection then sheds it

Researchers have discovered a tube-shaped structure that
forms temporarily in a certain type of virus to deliver its
DNA during the infection process and then dissolves after
its job is completed. The virus is pictured here infecting an
E. coli cell. The tube attaches to the cell's inner and outer
membranes, bridging the "periplasmic space" in between.
(Purdue University image/Lei Sun)
Researchers have discovered a tube-shaped structure that forms temporarily in a certain type of virus to deliver its DNA during the infection process and then dissolves after its job is completed.
The researchers discovered the mechanism in the phiX174 virus, which attacks E. coli bacteria. The virus, called a bacteriophage because it infects bacteria, is in a class of viruses that do not contain an obvious tail section for the transfer of its DNA into host cells.
"But, lo and behold, it appears to make its own tail," said Michael Rossmann, Purdue University's Hanley Distinguished Professor of Biological Sciences. "It doesn't carry its tail around with it, but when it is about to infect the host it makes a tail."
Researchers were surprised to discover the short-lived tail.
"This structure was completely unexpected," said Bentley A. Fane, a professor in the BIO5 Institute at the University of Arizona. "No one had seen it before because it quickly emerges and then disappears afterward, so it's very ephemeral."
Although this behavior had not been seen before, another phage called T7 has a short tail that becomes longer when it is time to infect the host, said Purdue postdoctoral research associate Lei Sun, lead author of a research paper to appear online in the journal Nature on Dec. 15.
The paper's other authors are University of Arizona research technician Lindsey N. Young; Purdue postdoctoral research associate Xinzheng Zhang and former Purdue research associate Sergei P. Boudko; Purdue assistant research scientist Andrei Fokine; Purdue graduate student Erica Zbornik; Aaron P. Roznowski, a University of Arizona graduate student; Ian Molineux, a professor of molecular genetics and microbiology at the University of Texas at Austin; Rossmann; and Fane.
Researchers at the BIO5 institute mutated the virus so that it could not form the tube. The mutated viruses were unable to infect host cells, Fane said.
The virus's outer shell, or capsid, is made of four proteins, labeled H, J, F and G. The structures of all but the H protein had been determined previously. The new findings show that the H protein assembles into a tube-shaped structure. The E. coli cells have a double membrane, and the researchers discovered that the two ends of the virus's H-protein tube attach to the host cell's inner and outer membranes.
Images created with a technique called cryoelectron tomography show this attachment. The H-protein tube was shown to consist of 10 "alpha-helical" molecules coiled around each other. Findings also showed that the inside of the tube contains a lining of amino acids that could be ideal for the transfer of DNA into the host.
"This may be a general property found in viral-DNA conduits and could be critical for efficient genome translocation into the host," Rossmann said.
Like many other viruses, the shape of the phiX174 capsid has icosahedral symmetry, a roughly spherical shape containing 20 triangular faces.
The research has been funded by the National Science Foundation, U.S. Department of Energy, and the U.S. Department of Agriculture.