Wednesday, March 9, 2011

New method for infectious diseases research

 Infectious diseases researchers at Umea University in Sweden are studying the surface properties of bacteria together with materials scientists. Studies of the outermost parts of the cell walls of bacteria yield new information about the chemical composition of structures that are important for the capacity of bacteria to infect organisms. The findings are now being reported in the Journal of Biological Chemistry.


When bacteria infect a host organism, they usually attach to tissue cells. Infectious diseases scientists at Umea University are studying structural details of the outermost layer of bacterial cells in order to find new substances that can prevent bacterial infections. In collaboration with materials researchers at the Department of Chemistry, they describe new methods that facilitate and speed up their studies.


Chemist Madeleine Ramstedt is pursuing research on a material with new properties that prevent bacteria from attaching to its surface. The new material would be optimal for equipment in health care, where biofilms of bacteria can be a source of infection. In her research, Madeleine Ramstedt uses spectroscopic methods, among others, that she is now making available to her colleagues in the research consortium Umea Centre for Microbial Research, UCMR.


Microbiologists Sun Nyunt Wai, Ryoma Nakao, and Bernt Eric Uhlin, together with chemists Jean-Fran├žois Boily and Madeleine Ramstedt, were investigating whether new physiochemical analysis methods could also be used for microbial studies. The scientists combined so-called cryo-x-ray photoelectron spectroscopy with multivariate analysis. This analysis yields specific patterns of intensity curves depending on the chemical composition of the surface of the material being studied.


"We've succeeded also in analyzing the cell surfaces of bacteria with our x-ray spectroscopy. We found strong patterns that we could clearly relate to different compositions in lipids, sugar, protein, and the polymer peptidoglycan in the cell wall of the bacterium that can affect the capacity of a bacterium to infect an organism," explains Madeleine Ramstedt. "The method makes it possible to analyze the outermost layer, about 10 nanometers from the surface."


"Our method is relatively simple in comparison with other methods in which the extraction of various cell components is needed. This means that with our method the surface of the bacteria can be examined under more natural conditions in an intact bacterial cell."


X-ray photoelectron spectroscopy has previously been used to study bacteria, but only to a limited extent. The Umea scientists have managed to optimize the method. "We shock freeze the bacteria and keep them frozen throughout the analysis. This allows us to assume that they do not change during the examination. Now it's possible to compare the cell walls in similar bacteria that have been treated in different ways or that have changed, for example by developing resistance. With our method we can now compare structures in cell walls in pathogenic bacteria with those of non-pathogenic bacteria, all on a larger scale. Hopefully this new method of analysis will yield more rapid results and provide infectious diseases researchers with new clues for finding new antibiotics," says Madeleine Ramstedt.


UCMR is one of Umea University's strong research environments. The centre is an interdisciplinary research consortium that brings together a number of research teams in microbial research with participation from chemistry, medical and clinical microbiology, molecular biology, physics, and bioinformatics.


Story Source:


The above story is reprinted (with editorial adaptations) from materials provided by Umea universitet, via AlphaGalileo.

Journal Reference:

M. Ramstedt, R. Nakao, S. N. Wai, B. E. Uhlin, J.-F. Boily. Monitoring surface chemistry changes in the bacterial cell wall - multivariate analysis of Cryo-X-ray photoelectron spectroscopy data. Journal of Biological Chemistry, 2011; DOI: 10.1074/jbc.M110.209536

Delving into manganite conductivity

 Chemical compounds called manganites have been studied for many years since the discovery of colossal magnetoresistance, a property that promises important applications in the fields of magnetic sensors, magnetic random access memories and spintronic devices. However, understanding -- and ultimately controlling -- this effect remains a challenge, because much about manganite physics is still not known. A research team lead by Maria Baldini from Stanford University and Carnegie Geophysical Laboratory scientists Viktor Struzhkin and Alexander Goncharov has made an important breakthrough in our understanding of the mysterious ways manganites respond when subjected to intense pressure.


At ambient conditions, manganites have insulating properties, meaning they do not conduct electric charges. When pressure of about 340,000 atmospheres is applied, these compounds change from an insulating state to a metallic state, which easily conducts charges. Scientists have long debated about the trigger for this change in conductivity.


The research team's new evidence, published online Feb. 11 in Physical Review Letters, shows that for the manganite LaMnO3, this insulator-to-metal transition is strongly linked to a phenomenon called the Jahn-Teller effect. This effect actually causes a unique distortion of the compound's structure. The team's measurements were carried out at the Geophysical Laboratory.


Counter to expectations, the Jahn-Teller distortion is observed until LaMnO3 is in a non-conductive insulating state. Therefore, it is reasonable to believe that the switch from insulator to metal occurs when the distortion is suppressed, settling a longstanding debate about the nature of manganite insulating state. The formation of inhomogeneous domains -- some with and some without distortion -- was also observed. This evidence suggests that the manganite becomes metallic when the breakdown of undistorted to distorted molecules hits a critical threshold in favor of the undistorted.


"Separation into domains may be a ubiquitous phenomenon at high pressure and opens up the possibility of inducing colossal magnetoresistance by applying pressure" said Baldini, who was with Stanford at the time the research was conducted, but has now joined Carnegie as a research scientist.


Some of the researchers were supported by various grants from the Department of Energy, Office of Science and National Nuclear Security Administration. Some of the experiments were supported by DOE and Carnegie Canada.


Story Source:


The above story is reprinted (with editorial adaptations ) from materials provided by Carnegie Institution.

Journal Reference:

M. Baldini, V. Struzhkin, A. Goncharov, P. Postorino, W. Mao. Persistence of Jahn-Teller Distortion up to the Insulator to Metal Transition in LaMnO3. Physical Review Letters, 2011; 106 (6) DOI: 10.1103/PhysRevLett.106.066402

Cements that self-repair cracks and store latent heat energy?

 Cement (and derivatives thereof) is one of the materials most commonly used in construction, given its good performance at low cost. Over recent years, one part of scientific and technological research is aimed at incorporating additional functions into these materials. Specifically, Doctor Idurre Kaltzakorta studied the possibility of adding capacities to the cement such as self-repair of cracks as well as storing latent heat energy.


Her PhD thesis, undertaken at Tecnalia's Construction Unit, was presented at the University of the Basque Country (UPV/EHU) and entitled: Synthesis of silica microcapsules encapsulating different organic compounds for addition in the cement paste.


As the title of her research suggests, Dr Kaltzakorta created silica (it is, for instance, the base of glass) microcapsules with organic material inside, the idea being to provide the cement with new functions. She opted for two types of organic materials, each corresponding to one of the two added features mentioned above. Thus, on the one hand, the microcapsules were filled with various epoxy resins (used in the manufacture of adhesives), to provide the cement with the capacity for the self-repair of cracks. On the other, phase change materials were encapsulated. These are materials which absorb or free a great quantity of heat on the phase of the material changing (from solid to liquid or liquid to gas and vice-versa), and enable the storage of latent heat energy in the cement material.


Sol-gel and emulsion


Ms Kaltzakorta studied the synthesis of the encapsulated material, opting for synthesising microcapsules by combining sol-gel chemistry with emulsion technology. This route enabled the encapsulation of organic material, difficult with other routes, under mild temperature and pressure conditions.


Once the microcapsules were obtained, the thesis analysed the effect of the addition of these to the cement matrix, to verify the viability of the technique. With this in mind, Ms Kaltzakorta used a number of techniques with which the features of the new cement material could be studied, techniques such as X-ray tomography, scanning electron microscopy, mechanical testing and differential scanning calorimetry.


In conclusion, the thesis shows the viability of the development of a new generation of cements capable of the self-repair of cracks as well as storing latent heat energy, based on the application of silica microcapsules with various organic materials. In fact, the research for developing the new cement with the capacity for self-sealing of cracks has given rise to a patent. Moreover, according to Ms Kaltzakorta, the proposal presented in this thesis is a commitment to sustainability. On the one hand, getting the cement material to self-repair increases the useful life of the structures. On the other, using a material capable of regulating the temperature within the buildings will enhance their energy efficiency.


Story Source:


The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Basque Research.

A mix of tiny gold and viral particles, and the DNA ties that bind them

Scientists have created a diamond-like lattice composed of gold nanoparticles and viral particles, woven together and held in place by strands of DNA. The structure -- a distinctive mix of hard, metallic nanoparticles and organic viral pieces known as capsids, linked by the very stuff of life, DNA -- marks a remarkable step in scientists' ability to combine an assortment of materials to create infinitesimal devices.


The research, done by scientists at the University of Rochester Medical Center, Scripps Research Institute, and Massachusetts Institute of Technology, was published recently in Nature Materials.


While people commonly think of DNA as a blueprint for life, the team used DNA instead as a tool to guide the precise positioning of tiny particles just one-millionth of a centimeter across, using DNA to chaperone the particles.


Central to the work is the unique attraction of each of DNA's four chemical bases to just one other base. The scientists created specific pieces of DNA and then attached them to gold nanoparticles and viral particles, choosing the sequences and positioning them exactly to force the particles to arrange themselves into a crystal lattice.


When scientists mixed the particles, out of the brew emerged a sodium thallium crystal lattice. The device "self assembled" or literally built itself.


The research adds some welcome flexibility to the toolkit that scientists have available to create nano-sized devices.


"Organic materials interact in ways very different from metal nanoparticles. The fact that we were able to make such different materials work together and be compatible in a single structure demonstrates some new opportunities for building nano-sized devices," said Sung Yong Park, Ph.D., a research assistant professor of Biostatistics and Computational Biology at Rochester.


Park and M.G Finn, Ph.D., of Scripps Research Institute are corresponding authors of the paper.


Such a crystal lattice is potentially a central ingredient to a device known as a photonic crystal, which can manipulate light very precisely, blocking certain colors or wavelengths of light while letting other colors pass. While 3-D photonic crystals exist that can bend light at longer wavelengths, such as the infrared, this lattice is capable of manipulating visible light. Scientists foresee many applications for such crystals, such as optical computing and telecommunications, but manufacturing and durability remain serious challenges.


It was three years ago that Park, as part of a larger team of colleagues at Northwestern University, first produced a crystal lattice with a similar method, using DNA to link gold nanospheres. The new work is the first to combine particles with such different properties -- hard gold nanoparticles and more flexible organic particles.


Within the new structure, there are actually two distinct forces at work, Park said. The gold particles and the viral particles repel each other, but their deterrence is countered by the attraction between the strategically placed complementary strands of DNA. Both phenomena play a role in creating the rigid crystal lattice. It's a little bit like how countering forces keep our curtains up: A spring in a curtain rod pushes the rod to lengthen, while brackets on the window frame counter that force, creating a taut, rigid device.


Other authors of the paper include Abigail Lytton-Jean, Ph.D., of MIT, Daniel Anderson, Ph.D., of Harvard and MIT, and Petr Cigler, Ph.D., formerly of Scripps Research Institute and now at the Academy of Sciences of the Czech Republic. Park's work was supported by the National Institute of Allergy and Infectious Diseases.


Story Source:


The above story is reprinted (with editorial adaptations) from materials provided by University of Rochester Medical Center.

Journal Reference:

Petr Cigler, Abigail K. R. Lytton-Jean, Daniel G. Anderson, M. G. Finn, Sung Yong Park. DNA-controlled assembly of a NaTl lattice structure from gold nanoparticles and protein nanoparticles. Nature Materials, 2010; 9 (11): 918 DOI: 10.1038/nmat2877

DNA engine observed in real-time traveling along base pair track

 In a complex feat of nanoengineering, a team of scientists at Kyoto University and the University of Oxford have succeeded in creating a programable molecular transport system, the workings of which can be observed in real time. The results, appearing in the latest issue of Nature Nanotechnology, open the door to the development of advanced drug delivery methods and molecular manufacturing systems.


Resembling a monorail train, the system relies on the self-assembly properties of DNA origami and consists of a 100 nm track together with a motor and fuel. Using atomic force microscopy (AFM), the research team was able to observe in real time as this motor traveled the full length of the track at a constant average speed of around 0.1 nm/s.


"The track and motor interact to generate forward motion in the motor," explained Dr. Masayuki Endo of Kyoto University's Institute for Integrated Cell-Material Sciences (iCeMS). "By varying the distance between the rail 'ties,' for example, we can adjust the speed of this motion."


The research team, including lead author Dr. Shelley Wickham at Oxford, anticipates that these results will have broad implications for future development of programable molecular assembly lines leading to the creation of synthetic ribosomes.


"DNA origami techniques allow us to build nano- and meso-sized structures with great precision," elaborated iCeMS Prof. Hiroshi Sugiyama. "We already envision more complex track geometries of greater length and even including junctions. Autonomous, molecular manufacturing robots are a possible outcome."


The article was published online in the February 6, 2011 issue of Nature Nanotechnology.


Funding for this research was provided by the Engineering and Physical Sciences Research Council (EP/G037930/1), the Clarendon Fund, the Oxford-Australia Scholarship Fund, the CREST program of the Japan Science and Technology Agency (JST), and the Japanese Ministry of Education, Culture, Sports, Science and Technology (MEXT).


Story Source:


The above story is reprinted (with editorial adaptations ) from materials provided by Institute for Integrated Cell-Material Sciences, Kyoto University, via EurekAlert!, a service of AAAS.

Journal Reference:

Shelley F. J. Wickham, Masayuki Endo, Yousuke Katsuda, Kumi Hidaka, Jonathan Bath, Hiroshi Sugiyama, Andrew J. Turberfield. Direct observation of stepwise movement of a synthetic molecular transporter. Nature Nanotechnology, 2011; DOI: 10.1038/nnano.2010.284

How voltage breaks down plastic: Creasing to cratering

A Duke University team has seen for the first time how soft polymers, such as wire insulation, can break down under exposure to electrical current.


Researchers have known for decades that polymers, such those insulating wires, may break down due to deformation of the polymers. But the process had never been seen.


In a series of experiments, Duke University engineers have documented at the microscopic level how plastic deforms to breakdown as it is subjected to ever-increasing electric voltage. Polymers can be found almost everywhere, most commonly as an insulator for electrical wires, cables and capacitors.


The findings by the Duke engineers could help in developing new materials to improve the durability and efficiency of any polymer that must come into contact with electrical currents, as well as in the emerging field of energy harvesting.


"We have long known that these polymers will eventually break down, or fail, when subjected to an increasing electrical voltage," said Xuanhe Zhao, assistant professor of mechanical engineering and materials science at Duke's Pratt School of Engineering. He is the senior scientist in the series of experiments performed by a graduate student Qiming Wang and published online in the Physical Review Letters. "Now we can actually watch the process as it happens in real time."


The innovation the Duke team developed was attaching the soft polymer to another rigid polymer layer, or protective substrate, which enabled observation of the deformation process without incurring the breakdown. They then subjected this polymer-substrate unit to various electrical voltages and observed the effects under a microscope.


"As bread dough rises in a bowl, the top surface of the dough may fold in upon itself to form creases due to compressive stresses developing in the dough," Zhao said, "Surprisingly, this phenomenon may be related to failures of electrical polymers that are widely used in energy-related applications."


"When the voltage reached a critical point, the compressive stress induced a pattern of creases, or folds, on the polymer," Zhao. "If the voltage is increased further, the creases evolved into craters or divots in the polymer as the electrical stress pulls the creases open. Polymers usually break down electrically immediately after the creasing, which can cause failures of insulating cables and organic capacitors."


The substrate the researchers developed for the experiments not only allowed for the visualization of the creasing-to-cratering phenomenon, it could also be the foundation of a new approach to improving the ability of wires to carry electricity.


The research was supported by startup funds provided by Pratt.


Story Source:


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