Terahertz wave activates filamentation of actin: A novel possibility of manipulating cellular functions Read more at: https://phys.org/news/2018-08-terahertz-filamentation-actin-possibility-cellular.html#jCp

Credit: Tohoku University

https://phys.org/news/2018-08-terahertz-filamentation-actin-possibility-cellular.html

A team of researchers has discovered that terahertz (THz) wave irradiation activates the filamentation of actin protein. Drs. Shota Yamazaki and Masahiko Harata (Graduate School of Agricultural Science, Tohoku University); Dr. Yuichi Ogawa (Graduate School of Agriculture, Kyoto University); Dr. Hiromichi Hoshina (THz imaging and the sensing team at RIKEN); and Dr. Toshitaka Idehara (FIR-UF at University of Fukui) have made this important discovery, which offers a new possibility for the manipulation of cellular functions.

Actin forms filaments through its polymerization in cells, and functions as a major component of cellular architecture. Actin plays a central role in various cellular functions, including wound healing and the metastasis of cancer cells. In addition, a portion of actin exists in the cell nucleus and regulates gene regulation. For example, actin is required for gene reprograming, which is required for establishing iPS (induced pluripotent) cells. In this research, the polymerization reaction of purified actin protein was monitored under irradiation of THz wave, and it was found that the THz wave activates the filamentation of actin.Due to the recent development of high power THz (1012 Hz) wave sources, many researchers have begun to explore its application for material manipulation. One of the advantages of THz wave irradiation is its lower photon energy as compared to visible light. Therefore, THz wave prevents the ionization of molecules. THz wave enables "soft" manipulation of macromolecules such as proteins, enabling changes to their higher-order structure without damaging the samples.

Actin governs various functions of cells. Therefore, a variety of drugs have been developed for controlling actin filamentation, and applications of these drugs for medical purposes have been explored. However, these drugs are inefficient in their delivery into, and clearance from, cells. THz irradiation is a non-invasive method and could overcome these identified problems in drugs. THz wave is expected to become a novel tool for the manipulation of cellular functions through modifying actin filamentation. This research team is now trying to understand the basic mechanism of the THz assisting filamentation to extend this technology to various proteins so that THz irradiation can be widely applied to various biological technologies.

OT-SpectroscopyNOW blog-Phosphorene: Two-dimensional Raman

 Phosphorene: Two-dimensional Raman

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http://www.spectroscopynow.com/raman/details/highlight/14de3301024/Last-Months-Most-Accessed-Feature-Phosphorene-Two-dimensional-Raman.html

Flat out phosphorus

Raman spectroscopy and transmission electron microscopy have been used by an international team to investigate the phosphorus analogue of graphene, the two-dimensional phosphane, known as phosphorene.

Phosphorene has potential applications in a new class of semiconducting transistor for that perennial aspiration, the ever faster and more powerful computer of the future. Unfortunately, while phosphorene can conduct electrons its ability to do so is anisotropic, meaning it depends on which way you orient it relative to the system as to whether it does so or not. Thus, a quick and simple way to determine the orientation of the material was needed for experimental setups and now, a team comprising researchers from the Massachusetts Institute of Technology, the Rensselaer Polytechnic Institute (RPI) in Troy, New York state, Tohoku University in Japan, Oak Ridge National Laboratory, Tennessee and the University of Pennsylvania, has done just that. There approach accurately determines orientation by examining the interaction between light and electrons within phosphorene or other thin layers of black phosphorus.

Calculated approach

Materials scientists have been studying phosphorene intently since it was first isolated in 2014. RPI's Vincent Meunier and his team confirmed the structure of phosphorene that same year. "This is a really interesting material because, depending on which direction you do things, you have completely different properties," explains Meunier, a phenomenon that might of course be exploited in devices. "But because it's such a new material, it's essential that we begin to understand and predict its intrinsic properties."

Meunier and colleagues have now built on the theoretical modelling and prediction of the properties of phosphorene using Rensselaer's supercomputer in the Center for Computational Innovations (CCI). On the basis of their calculations, they have home in on certain features of this novel material that will ultimately help physicists and materials scientists better understand it and thence technologists make use of those properties.

Writing in the journal ACS Nano Letters, the team initially set out to refine an existing technique for determining the orientation of the crystal using Raman spectroscopy. The team were reviewing their Raman data and spotted a few unexplained inconsistencies. So, they next turned to obtaining images of the orientation of their crystalline samples using Transmission Electron Microscopy (TEM), and lined these up with the "images" gleaned from the Raman results. As a topographic technique, TEM offers a definitive determination of the orientation of a crystal, but takes a lot more effort than recording a Raman spectrum. Nevertheless, the comparison revealed that electron-phonon interactions alone did not account for the orientation of the crystal. And the reason why led the way to yet another anisotropy of phosphorene - that of interactions between photons of light and electrons in the crystal.

Intrinsic anisotropy

The Raman spectrum should be intrinsic to the material and thus show the anisotropy of phosphorene. "But, it turns out that if you shine the light in different directions, you get different results, because the interaction between the light and the electrons in the material - the electron-photon interaction - is also anisotropic, but in a non-commensurate way," explains Meunier. The team suspected that phosphorene was anisotropic with respect to electron-photon interactions, but hadn't quite anticipated the significance of the property. "Usually electron-photon anisotropy doesn’t make such a big difference, but here, because we have such a particular chemistry on the surface and such a strong anisotropy, it's one of those materials where it makes a huge difference," Meunier adds.

Fundamentally, the discovery reveals a limitation in what current interpretation of Raman spectra can achieve in studying these materials. "It turns out that it's not so easy to use Raman vibrations to find out the direction of the crystal," Meunier explains. "But, and this is the beautiful thing, what we found is that the electron-photon interaction (which can be measured by recording the amount of light absorbed) - the interaction between the electrons and the laser - is a good predictor of the direction. Now you can really predict how the material will behave as a function of excitement with an outside stimulus."

Meunier worked with Mildred Dresselhaus of the Massachusetts Institute of Technology, as well as colleagues at Tohoku University in Japan, Oak Ridge National Laboratory, Tennessee and the University of Pennsylvania.

PC steel wires on concrete and steel bridges now visible with terahertz waves

Credit: Tohoku University

http://phys.org/news/2015-12-pc-steel-wires-concrete-bridges.html#jCp

Researchers at Tohoku University have found a way to make covered or hidden PC steel wires visible, by developing a new terahertz wave light source featuring both light and radio-wave characteristics

This new technology will be especially useful in the safety inspection of extradosed and other types of bridges that use PC steel wires hidden inside external cables covered by resin jackets.

External cables are important structural elements for dispersing loads in extradosed bridges and they have extremely high levels of safety with regard to corrosion. This is due to the fact that they are protectively covered in polyethylene resin or similar resins. (see fig. 1 and 2)

Destructive inspections, in which the outer coating is removed from the cable, run the risk of water and other forms of moisture penetrating the wires and causing corrosion after the inspection has been completed.

The technology developed by Professor Yutaka Oyama and his team at the Graduate School of Engineering, is a unique optical measurement system comprising a digital device terahertz light source and a laser terahertz light source with high penetrative capabilities for polyethylene resin and similar resins.

Fig.1 (above): Schematic structure and cross sectional view of PC steel cable. Steel cable is fully sealed by polyethylene. Fig.2: This sealed structure is similar to that of insulated electric conductive cable with Cu or Al bundled wires. …more

This enables non-destructive imaging of the inside of PC steel wire to be carried out without removing the external resin cover by making use of the terahertz wave characteristics that efficiently reflect metal surfaces within the resin. (see fig. 3 and 4)

The team also found that contrary to the radioactive rays conventionally used for non-destructive detection purposes, the new terahertz waves have no adverse effects on the human body.

Part of the results of this research was first announced at the 2015 CLEO (Conference on Lasers and Electro-Optics) Pacific Rim Conference held in Busan, South Korea, in August.

Fig.3 (above): Photograph of 60mm diameter PC steel cable for bridge construction and cross sectional structure. Fig.4: THz imaging of PC steel cable corresponding to the sealed and unsealed parts of the cable. Polyethylene outer mold was partially removed. Credit: Tohoku University

 Explore further: NEC demonstrates Terahertz camera for effective fire scene imaging

Penta-graphene, a new structural variant of carbon, discovered

The newly discovered material, called penta-graphene, is a single layer of carbon pentagons that resembles the Cairo tiling, and that appears to be dynamically, thermally and mechanically stable. Credit: Virginia Commonwealth University

 http://phys.org/news/2015-02-penta-graphene-variant-carbon.html#jCp

by Brian Mcneill

Researchers at Virginia Commonwealth University and universities in China and Japan have discovered a new structural variant of carbon called "penta-graphene" - a very thin sheet of pure carbon that has a unique structure inspired by a pentagonal pattern of tiles found paving the streets of Cairo.
The newly discovered material, called penta-graphene, is a single layer of carbonpentagons that resembles the Cairo tiling, and that appears to be dynamically, thermally and mechanically stable.

"The three last important forms of carbon that have been discovered were fullerene, the nanotube and graphene. Each one of them has unique structure. Penta-graphene will belong in that category," said the paper's senior author, Puru Jena, Ph.D., distinguished professor in the Department of Physics in VCU's College of Humanities and Sciences.

The researchers' paper, "Penta-Graphene: A New Carbon Allotrope," will appear in the journal Proceedings of the National Academy of Sciences, and is based on research that was launched at Peking University and VCU.

Qian Wang, Ph.D., a professor at Peking University and an adjunct professor at VCU, was dining in a restaurant in Beijing with her husband when she noticed artwork on the wall depicting pentagon tiles from the streets of Cairo.

"I told my husband, "Come, see! This is a pattern composed only of pentagons,'" she said. "I took a picture and sent it to one of my students, and said, 'I think we can make this. It might be stable. But you must check it carefully.' He did, and it turned out that this structure is so beautiful yet also very simple."

Most forms of carbon are made of hexagonal building blocks, sometimes interspersed with pentagons. Penta-graphene would be a unique two-dimensional carbon allotrope composed exclusively of pentagons.

Along with Jena and Wang, the paper's authors include Shunhong Zhang, Ph.D candidate, from Peking University; Jian Zhou, Ph.D., a postdoctoral researcher at VCU; Xiaoshuang Chen, Ph.D., from the Chinese Academy of Science in Shanghai; and Yoshiyuki Kawazoe, Ph.D., from Tohoku University in Sendai, Japan.

The researchers simulated the synthesis of penta-graphene using computer modelling. The results suggest that the material might outperform graphene in certain applications, as it would be mechanically stable, possess very high strength, and be capable of withstanding temperatures of up to 1,000 degrees Kelvin.

"You know the saying, diamonds are forever? That's because it takes a lot of energy to convert diamond back into graphite," Jena said. "This will be similar."

Penta-graphene has several interesting and unusual properties, Jena said. For example, penta-graphene is a semiconductor, whereas graphene is a conductor of electricity.

"When you take graphene and roll it up, you make what is called a carbon nanotubewhich can be metallic or semiconducting," Jena said. "Penta-graphene, when you roll it up, will also make a nanotube, but it is always semiconducting."

The way the material stretches is also highly unusual, the researchers said.

"If you stretch graphene, it will expand along the direction it is stretched, but contract along the perpendicular direction." Wang said. "However, if you stretch penta-graphene, it will expand in both directions."

The material's mechanical strength, derived from a rare property known as Negative Poisson's Ratio, may hold especially interesting applications for technology, the researchers said.

Penta-graphene's properties suggest that it may have applications in electronics, biomedicine, nanotechnology and more.

The next step, Jena said, is for scientists to synthesize penta-graphene.

"Once you make it, it [will be] very stable. So the question becomes, how do you make it? In this paper, we have some ideas. Right now, the project is theoretical. It's based on computer modelling, but we believe in this prediction quite strongly. And once you make it, it will open up an entirely new branch of carbon science. Two-dimensional carbon made completely of pentagons has never been known."

 Explore further: Researchers make magnetic graphene

More information: Proceedings of the National Academy of Sciences,www.pnas.org/content/early/2015/01/27/1416591112

Journal reference: Proceedings of the National Academy of Sciences  

Provided by Virginia Commonwealth University  

Bottom-Up Self Assembly of Graphene Holds Promise for Spintronics

                                    Image: Patrick Han
http://spectrum.ieee.org/nanoclast/semiconductors/materials/bottomup-self-assembly-of-graphene-holds-promise-for-spintronic-applications
By Dexter Johnson 

Not all graphene is alike. The way in which graphene is produced determines in large measure how it can be applied. The aim, of course, has been to produce the best quality graphene in large quantities.

However, these bulk production methods come at a price, which usually involves compromising those astounding electronic properties that make graphene so attractive in the first place.

Now researchers at the University of California Los Angeles (UCLA) and Tohoku University in Japan may have found a way around these limitations by abandoning “top-down” manufacturing techniques like lithography for a bottom-up approach in which the graphene nanoribbons self assemble exactly into the desired form.

The researchers were looking for a way to produce graphene nanoribbons that have the zigzag edges that give the material a strong magnetic property, making it attractive for spintronics. Spintronics exploits the way in which the spin of particles respond to magnetic fields so that the spin is either parallel or antiparallel to the magnetic field. These two possibilities make it useful for creating a digital signal that can be used in computing.

“To make devices out of graphene, we need to control its geometric and electronic structures,” said Paul Weiss of UCLA in a press release. “Making zigzag edges does both of these simultaneously, as there are some special properties of graphene nanoribbons with zigzag edges. Having these in hand will enable us to test theoretical predictions about them, such as magnetic properties.”

The typical lithographic method for producing graphene nanoribbons with these zigzag edges resulted in too many defects in the final product for the material to be useful.

In the research, which was published in the journal ACS Nano, the team exploited the properties of a copper substrate to alter the way the graphene precursor molecules reacted to each other as they assembled into graphene nanoribbons. With this method, the researchers were able to control the length, edge configuration, and location of the nanoribbons on the substrate.

This isn’t the first time that graphene nanoribbons were produced by self-assembly, but in earlier efforts the end results were bundles of ribbons that needed to go through another process to untangle them and position them in a device.

“Previous strategies in bottom-up molecular assemblies used inert substrates, such as gold or silver, to give molecules a lot of freedom to diffuse and react on the surface,” said Patrick Han of Tohoku University in the press release. “But this also means that the way these molecules assemble is completely determined by the intermolecular forces and by the molecular chemistry. Our method opens the possibility for self-assembling single-graphene devices at desired locations, because of the length and the direction control.”