Nature
-
Broadband and Ultrathin Polarization Manipulators Developed
Professor Bumki Min from the Department of Mechanical Engineering at KAIST has developed a technology that can manipulate a polarized light in broadband operation with the use of a metamaterial.
It is expected that this technology will lead to the development of broadband optical devices that can be applied to broadband communication and display.
When an object or its structure is analyzed by using a polarized light such as a laser, the results are generally affected by the polarized state of the light. Therefore, in an optics laboratory, the light is polarized by various methods.
In such cases, researchers employ wave plates or photoactive materials. However, the performance of these devices depend vastly on wavelength, and so they are not suitable to be used as a polarizer, especially in broadband.
There were many attempts to make artificial materials that are very photoactive by using metamaterials which have a strong resonance. Nonetheless, because the materials had an unavoidable dispersion in the resonance frequency, they were not adequate for broadband operation.
Professor Min’s research team arranged and connected helical metamaterials that are smaller than the wavelength of light. They verified theoretically and experimentally that polarized light can be constantly rotated regardless of the wavelength by super-thin materials that have thickness less than one-tenth of the wavelength of the light. The experiment which confirmed the theory was conducted in the microwave band.
Broadband polarized rotational 3D metamaterials were found to rotate the polarized microwave within the range of 0.1 GHz to 40 GHz by 45 degrees regardless of its frequency. This nondispersive property is quite unnatural because it is difficult to find a material that does not change in a wide band.
In addition, the research team materialized the broadband nondispersive polarized rotational property by designing the metamaterial in a way that it has chirality, which determines the number of rotations proportional to the wavelength.
Professor Min said, “As the technology is able to manipulate ultrathin polarization of light in broadband, it will lead to the creation of ultra-shallow broadband optical devices.”
Sponsored by the Ministry of Science, ICT and Future Planning of the Republic of Korea and the National Research Foundation of Korea, this research was led by a PhD candidate, Hyun-Sung Park, under the guidance of Professor Min. The research findings were published online in the November 17th issue of Nature Communications.
Figure 1 – Broadband and Ultrathin Polarization Manipulators Produced by 3D Printer
Figure 2 – Concept of Broadband and Ultrathin Polarization Manipulators
2014.12.03 View 8558 -
Structure of Neuron-Connecting Synaptic Adhesion Molecules Discovered
A research team has found the three-dimensional structure of synaptic adhesion molecules, which orchestrate synaptogenesis. The research findings also propose the mechanism of synapses in its initial formation. Some brain diseases such as obsessive compulsive disorder (OCD) or bipolar disorders arise from a malfunction of synapses. The team expects the findings to be applied in investigating pathogenesis and developing medicines for such diseases.
The research was conducted by a Master’s candidate Kee Hun Kim, Professor Ji Won Um from Yonsei University, and Professor Beom Seok Park from Eulji University under the guidance of Professor Homin Kim from the Graduate School of Medical Science and Engineering, KAIST, and Professor Jaewon Ko from Yonsei University. Sponsored by the Ministry of Science, ICT and Future Planning and the National Research Foundation of Korea, the research findings were published online in the November 14th issue of Nature Communications.
A protein that exists in the neuronal transmembrane, Slitrk, interacts with the presynaptic leukocyte common antigen-related receptor protein tyrosine phosphatases (LAR-RPTPs) and forms a protein complex. It is involved in the development of synapses in the initial stage, and balances excitatory and inhibitory signals of neurons.
It is known that a disorder in those two proteins cause a malfunction of synapses, resulting in neuropsychosis such as autism, epilepsy, OCD, and bipolar disorders. However, because the structure as well as synaptogenic function of these proteins were not understood, the development of cures could not progress.
The research team discovered the three-dimensional structure of two synaptic adhesion molecules like Slitrk and LAR-RPTPs and identified the regions of interaction through protein crystallography and transmission electron microscopy (TEM). Furthermore, they found that the formation of the synapse is induced after the combination of two synaptic adhesion molecules develops a cluster.
Professor Kim said, “The research findings will serve as a basis of understanding the pathogenesis of brain diseases which arises from a malfunction of synaptic adhesion molecules. In particular, this is a good example in which collaboration between structural biology and neurobiology has led to a fruitful result.” Professor Ko commented that “this will give new directions to synaptic formation-related-researches by revealing the molecular mechanism of synaptic adhesion molecules.”
Figure 1: Overview of the PTPd Ig1–3/Slitrk1 LRR1 complex.
Figure 2: Representative negative-stained electron microscopy images of Slitrk1 Full ectodomain (yellow arrows indicate the horseshoe-shaped LRR domains). The typical horseshoe-shaped structures and the randomness of the relative positions of each LRR domain can be observed from the two-dimensional class averages displayed in the orange box.
Figure 3: Model of the two-step presynaptic differentiation process mediated by the biding of Slitrks to LAR-RPTPs and subsequent lateral assembly of trans-synaptic LAR-RPTPs/Slitrik complexes.
2014.11.28 View 9039 -
Professor YongKeun Park Produces Undergraduate Students with International Achievements
Three undergraduate students under the supervision of Professor YongKeun Park from the Department of Physics, KAIST, have published papers in globally renowned academic journals.
The most recent publication was made by YoungJu Jo, a senior in physics. Jo’s paper entitled “Angle-resolved light scattering of individual rod-shaped bacteria based on Fourier transform light scattering” was published in the May 28th edition of Scientific Reports.
Analyzing bacteria is a very important task in the field of health and food hygiene, but using the conventional biochemical methods of analysis takes days. However, observation with Jo’s newly developed method using light scattering analyzes bacteria within a matter of seconds.
SangYeon Cho from the Department of Chemistry also published papers in Cell (2012) and Nature (2013), respectively, under the guidance of Professor Park. SangYeon Cho’s outstanding research achievements were recognized by Harvard and MIT. He was accepted with a full scholarship to Harvard-MIT Health Sciences and Technology Graduate School. He will begin his graduate studies at Harvard-MIT this September.
Last March, SeoEun Lee from the Department of Biology was the recipient of the Best Paper Award by the Optical Society of Korea. She plans to pursue a doctoral degree at the College of Physicians and Surgeons, Columbia University in New York.
Professor Park said, “Undergraduate students, who are learning a variety of subjects concurrently, are at the most creative time of their lives. KAIST has offered many opportunities to undergraduate students to partake in various research programs.”
- Picture (a) and (b): Rod-shaped bacteria’s phase image and light-scattering patterns
- Picture (c): Quantitative analysis to illustrate the extraction of information from bacteria
2014.06.03 View 8854 -
KAIST Top in the Nature Publishing Index 2013 Asia-Pacific
The Nature Publishing Index 2013 Asia-Pacific has been released today. The index is a supplement to Nature, which measures the output of research articles from nations and institutes published in the 18 Nature-branded primary research journals over the calendar year.
A press release from the Nature Publishing Group follows below:
South Korea regains scientific impetus
PRESS RELEASE FROM NATURE PUBLISHING GROUP
Embargoed until 03.00 KST on Thursday 27 March 2014
South Korea ranks fourth for scientific research output in the region, according to the Nature Publishing Index 2013 Asia-Pacific released today.
In 2013, the nation significantly increased its NPI output following a slight drop in 2012.
Named a possible ‘one to watch’ by the supplement editors, with high levels of investment in science and technology announced by both government and private enterprise, its NPI output is growing faster than China’s.
The Korea Advanced Institute of Science and Technology has risen two places to take top spot above Seoul National University, which has retained second place. Pohang University of Science and Technology has leapt from eighth to third, with a more-than-threefold increase in corrected count, adjusted for the proportional contribution of collaborative institutions.
Last year’s number one, Yonsei University, could not maintain its exceptional 2012 NPI output and has dropped to seventh spot.
It is now just above a newcomer, the Institute for Basic Science (IBS), funded as part of the government’s increased investment in basic science. IBS plans to open 50 research centres by 2017 and will no doubt provide increasing contributions in the next few years.
To see the latest results for the region, and the Nature Publishing Index Global Top 100, visit the Index website at
www.natureasia.com/en/publishing-index.
The data posted on the website is updated every week with a moving window of 12 months of data.
2014.03.27 View 5750 -
Professor Sang-Ouk Kim Publishes Review Article in the Journal of "Nature Materials"
Nature Materials, a
peer-reviewed scientific journal published by Nature Publishing Group, covers a
range of topics within materials science from materials engineering and
structural materials. The
journal invited Professor Sang-Ouk Kim of Materials Science and Engineering at
KAIST to contribute to the April issue of 2014. Professor Kim,
together with his doctoral student, Ju-Young Kim, wrote a review article in the
“News and Views” section of the journal, which was entitled “Liquid Crystals:
Electric Fields Line Up Graphene Oxide.” The
News and Views is a peer-reviewed section where an academic authority in a particular
field reviews and evaluates papers published in the journal. In
the article, Professor Kim reviewed a paper written by Jang-Kun Song et al. and
highlighted important research outcomes such as the efficient electric field switching
of graphene oxide (GO) liquid-crystals in low-concentration dispersions and the
demonstration of a prototype of a GO liquid-crystal display. This technology
could lead the development of a flexible display. Professor
Kim is an eminent scholar who has reported for the first time in the world on
the solvent-based graphene oxide liquid crystals formation in 2011. For the article, please go to: http://www.kaist.ac.kr/_prog/download.php?filename=Nature_Materials_Professor_Sang-Ouk_Kim_Apr_2014.pdf
2014.03.26 View 7384 -
A research paper by Professor Myung-Chul Choi reviewed in Science (February 28, 2014)
A research paper entitled “Transformation of taxol-stabilized microtubules into inverted tubulin tubules triggered by a tubulin conformation switch” was published in
Nature Materials
this year, dated January 19, 2014.
Professor Myung-Chul Choi and Dr. Chae-Yeon Song from the Department of Bio and Brain Engineering at KAIST co-authored the paper together with researchers from the University of California in Santa Barbara and the Hebrew University of Jerusalem.
Science,
dated February 28, 2014, has recently reviewed the paper in its section called "Perspectives."
2014.03.13 View 7157 -
Spillover Phenomenon Identified Using Model Catalyst System
Researchers at KAIST have identified spillover phenomenon, which has remained controversial since its discovery in the early 1960s.
KAIST Department of Chemical and Biomolecular Engineering’s Professor Min-Gi Choi and his team has explained the "spillover phenomenon," using their own model catalyst system where platinum is selectively located within the amorphous aluminosilicate.
The research results were published on the 25th February online edition of Nature Communications.
Spillover refers to a phenomenon that occurs when hydrogen atoms that have been activated on the surface of metals, such as platinum, move to the surface of the catalyst. It was predicted that this phenomenon can be used to design a catalyst with high activity and stability, and thus has been actively studied over the last 50 years.
However, many cases of the known catalysts involved competing reactions on the exposed metal surface, which made it impossible to directly identify the presence and formation mechanism of spillover.
The catalysts developed by the researchers at KAIST used platinum nanoparticles covered with aluminosilicate. This only allowed the hydrogen molecules to pass through and has effectively blocked the competing reactions, enabling the research team to study the spillover phenomenon.
Through various catalyst structure and reactivity analysis, as well as computer modeling, the team has discovered that Brönsted acid sites present on the aluminosilicate plays a crucial role in spillover phenomenon.
In addition, the spillover-based hydrogenation catalyst proposed by the research team showed very high hydrogenation and dehydrogenation activity. The ability of the catalyst to significantly inhibit unwanted hydrogenolysis reaction during the petrochemical processes also suggested a large industrial potential.
Professor Min-Gi Choi said, “This particular catalyst, which can trigger the reaction only by spillover phenomenon, can be properly designed to exceed the capacity of the conventional metal catalysts. The future goal is to make a catalyst with much higher activity and selectivity.”
The research was conducted through funds subsidized by SK Innovation and Ministry of Science, ICT and Future Planning.
The senior research fellow of SK Innovation Seung-Hun Oh said, “SK Innovation will continue to develop a new commercial catalyst based on the technology from this research.”
Juh-Wan Lim and Hye-Yeong Shin led the research as joint first authors under supervision of Professor Min-Gi Choi and computer modeling works were conducted by KAIST EEWS (environment, energy, water, and sustainability) graduate school’s Professor Hyeong-Jun Kim.
2014.03.03 View 7530 -
A Molecular Switch Controlling Self-Assembly of Protein Nanotubes Discovered
International collaborative research among South Korea, United States, and Israel research institutionsThe key to the treatment of cancer and brain disease mechanism The molecular switch that controls the self-assembly structure of the protein nanotubes, which plays crucial role in cell division and intracellular transport of materials, has been discovered. KAIST Bio and Brain Engineering Department’s Professor Myeong-Cheol Choi and Professor Chae-Yeon Song conducted the research, in collaboration with the University of California in Santa Barbara, U.S., and Hebrew University in Israel. The findings of the research were published in Nature Materials on the 19th. Microtubules are tube shaped and composed of protein that plays a key role in cell division, cytoskeleton, and intercellular material transport and is only 25nm in diameter (1/100,000 thickness of a human hair). Conventionally, cancer treatment focused on disrupting the formation of microtubules to suppress the division of cancer cells. In addition Alzheimer’s is known to be caused by the diminishing of structural integrity of microtubules responsible for intercellular material transport which leads to failure in signal transfer. The research team utilized synchrotron x-ray scattering and transmission electron microscope to analyze the self assemble structure of protein nanotubes to subnanometer accuracy. As a result, the microtubules were found to assemble into 25nm thickness tubules by stacking protein blocks 4 x 5 x 8nm in dimension. In the process, the research team discovered the molecular switch that controls the shape of these protein blocks. In addition the research team was successful in creating a new protein tube structure. Professor Choi commented that they were successful in introducing a new paradigm that suggests the possibility of controlling the complex biological functions of human’s biological system with the simple use of physical principles. He commented further that it is anticipated that the findings will allow for the application of bio nanotubes in engineering and that this is a small step in finding the mechanism behind cancer treatment and neural diseases.
2014.02.03 View 8195 -
Mechanism in regulation of cancer-related key enzyme, ATM, for DNA damage and repair revealed
Professor Kwang-Wook Choi
A research team led by Professor Kwang-Wook Choi and Dr. Seong-Tae Hong from the Department of Biological Sciences at KAIST has successfully investigated the operational mechanism of the protein Ataxia Telangiectasia Mutated (ATM), an essential protein to the function of a crucial key enzyme that repairs the damaged DNA which stores biometric information. The results were published on December 19th Nature Communications online edition.
All organisms, including humans, constantly strive to protect the information within their DNA from damages posed by a number of factors, such as carbonized materials in our daily food intake, radioactive materials such as radon emitting from the cement of buildings or ultraviolet of the sunlight, which could be a trigger for cancer.
In order to keep the DNA information safe, the organisms are always carrying out complex and sophisticated DNA repair work, which involves the crucial DNA damage repair protein ATM. Consequently, a faulty ATM leads to higher risks of cancer.
Until now, academia predicted that the Translationally Controlled Tumor Protein (TCTP) will play an important role in regulating the function of ATM. However, since most of main research regarding TCTP has only been conducted in cultured cells, it was unable to identify exactly what mechanisms TCTP employs to control ATM.
The KAIST research team identified that TCTP can combine with ATM or increase the enzymatic activity of ATM. In addition, Drosophilia, one of the most widely used model organisms for molecular genetics, has been used to identify that TCTP and ATM play a very important role in repairing the DNA damaged by radiation. This information has allowed the researchers to establish TCTP’s essential function in maintaining the DNA information in cell cultures and even in higher organisms, and to provide specific and important clues to the regulation of ATM by TCTP.
Professor Kwang-Wook Choi said, “Our research is a good example that basic research using Drosophilia can make important contributions to understanding the process of diseases, such as cancer, and to developing adequate treatment.”
The research has been funded by the Ministry of Science, ICT and Future Planning, Republic of Korea, and the National Research Foundation of Korea.
Figure 1. When the amount of TCTP protein is reduced, cells of the Drosophila's eye are abnormally deformed by radiation. Scale bars = 200mm
Figure 2. When the amount of TCTP protein is reduced, the chromosomes of Drosophilia are easily broken by radiation. Scale bars = 10 mm.
Figure 3. When gene expressions of TCTP and ATM are reduced, large defects occur in the normal development of the eye. (Left: normal Drosophilia's eye, right: development-deficient eye)
Figure 4. ATM marks the position of the broken DNA, with TCTP helping to facilitate this reaction. DNA (blue line) within the cell nucleus is coiled around the histone protein (green cylinder). When DNA is broken, ATM protein attaches a phosphate group (P). Multiple DNA repair protein recognizes the phosphate as a signal that requires repair and gathers at the site.
2014.01.07 View 9399 -
Ultra-High Strength Metamaterial Developed Using Graphene
New metamaterial has been developed, exhibiting hundreds of times greater strength than pure metals.
Professor Seung Min, Han and Yoo Sung, Jeong (Graduate School of Energy, Environment, Water, and Sustainability (EEWS)) and Professor Seok Woo, Jeon (Department of Material Science and Engineering) have developed a composite nanomaterial. The nanomaterial consists of graphene inserted in copper and nickel and exhibits strengths 500 times and 180 times, respectively, greater than that of pure metals. The result of the research was published on the July 2nd online edition in Nature Communications journal.
Graphene displays strengths 200 times greater than that of steel, is stretchable, and is flexible. The U.S. Army Armaments Research, Development and Engineering Center developed a graphene-metal nanomaterial but failed to drastically improve the strength of the material.
To maximize the strength increased by the addition of graphene, the KAIST research team created a layered structure of metal and graphene. Using CVD (Chemical Vapor Deposition), the team grew a single layer of graphene on a metal deposited substrate and then deposited another metal layer. They repeated this process to produce a metal-graphene multilayer composite material, utilizing a single layer of graphene. Micro-compression tests within Transmission Electronic Microscope and Molecular Dynamics simulations effectively showed the strength enhancing effect and the dislocation movement in grain boundaries of graphene on an atomic level.
The mechanical characteristics of the graphene layer within the metal-graphene composite material successfully blocked the dislocations and cracks from external damage from traveling inwards. Therefore the composite material displayed strength beyond conventional metal-metal multilayer materials. The copper-graphene multilayer material with an interplanar distance of 70nm exhibited 500 times greater (1.5GPa) strength than pure copper. Nickel-graphene multilayer material with an interplanar distance of 100nm showed 180 times greater (4.0GPa) strength than pure nickel.
It was found that there is a clear relationship between the interplanar distance and the strength of the multilayer material. A smaller interplanar distance made the dislocation movement more difficult and therefore increased the strength of the material. Professor Han, who led the research, commented, “the result is astounding as 0.00004% in weight of graphene increased the strength of the materials by hundreds of times” and “improvements based on this success, especially mass production with roll-to-roll process or metal sintering process in the production of ultra-high strength, lightweight parts for automobile and spacecraft, may become possible.” In addition, Professor Han mentioned that “the new material can be applied to coating materials for nuclear reactor construction or other structural materials requiring high reliability.”
The research project received support from National Research Foundation, Global Frontier Program, KAIST EEWS-KINC Program and KISTI Supercomputer and was a collaborative effort with KISTI (Korea Institute of Science and Technology Information), KBSI (Korea Basic Science Institute), Stanford University, and Columbia University.
A schematic diagram shows the structure of metal-graphene multi-layers. The metal-graphene multi-layered composite materials, containing a single-layered graphene, block the dislocation movement of graphene layers, resulting in a greater strength in the materials.
2013.08.23 View 11035 -
Technology Developed to Control Light Scattering Using Holography
Published on May 29th Nature Scientific Reports online
Recently, a popular article demonstrated that an opaque glass becomes transparent as transparent tape is applied to the glass. The scientific principle is that light is less scattered as the rough surface of the opaque glass is filled by transparent tape, thereby making things behind the opaque glass look clearer.
Professor Yong-Keun Park from KAIST’s Department of Physics, in a joint research with MIT Spectroscopy Lab, has developed a technology to easily control light scattering using holography. Their results are published on Nature’s Scientific Reports May 29th online edition.
This technology allows us to see things behind visual obstructions such as cloud and smoke, or even human skin that is highly scattering, optically thick materials. The research team applied the holography technology that records both the direction and intensity of light, and controlled light scattering of obstacles lied between an observer and a target image. The team was able to retrieve the original image by recording the information of scattered light and reflecting the light precisely to the other side.This phenomenon is known as “phase conjugation” in physics. Professor Park’s team applied phase conjugation and digital holography to observe two-dimensional image behind a highly scattering wall. “This technology will be utilized in many fields of physics, optics, nanotechnology, medical science, and even military science,” said Professor Park. “This is different from what is commonly known as penetrating camera or invisible clothes.” He nevertheless drew the line at over-interpreting the technology, “Currently, the significance is on the development of the technology itself that allows us to accurately control the scattering of light."
Figure I. Observed Images
Figure II. Light Scattering Control
2013.07.19 View 6359 -
Neurotransmitter protein structure and operation principle identified
Professor Tae-Young Yoon
- Real-time measurement of structural change of bio-membrane fusion protein
- A new clue to degenerative brain diseases research
KAIST Physics Department’s Professor Tae-Young Yoon has successfully identified the hidden structure and operation mechanism of the SNARE protein, which has a central role in transporting neurotransmitters between neurons, using magnetic nanotweezers. SNARE protein’s cell membrane fusion function is closely related to degenerative brain diseases or neurological disorders such as Alzheimer’s. Hence, this research may provide a clue to the disease’s prevention and treatment.
Neurotransmission occurs when vesicles containing neurotransmitters fuse with cell membranes in neuron synapses. The SNARE protein is a cell-membrane fusion protein with a core role of releasing neurotransmitters. The academia speculated the SNARE protein would regulate the exchange of neurotransmitters, but its precise function and structure has been unknown. Professor Yoon’s research team developed an experimental technique using nanotweezers to measure physical changes to nanometer level by pulling and releasing each protein with force of 1 pN (piconewton). The research identified the existence of hidden SNARE protein"s intermediate structure. The process of withstanding and maintaining repulsive forces between bio-membranes in the hidden intermediate structure of SNARE to regulate the exchange of neurotransmitters has also been identified.
Professor Yoon’s research team developed an experimental technique using magnetic nanotweezers to measure physical changes of proteins to nanometer level by pulling and releasing each protein with force of 1 pN. The research identified the existence of hidden SNARE protein"s intermediate structure and its formation. The process of withstanding and maintaining repulsive forces between bio-membranes in the hidden intermediate structure of SNARE to regulate the exchange of neurotransmitters has also been discovered.
Professor Yoon said, “Ground breaking research results have been produced. A simple experimental technique of applying the smallest possible forces to proteins (with tweezers) to see their hidden structure and formation process can produce the same result as real observation has been developed.” He continued, “This technique will be very important in researching biological object with physical experimental technique. It will be a vital foundation to consilient research of different academia in the future.”
This research was a joint project of Physics Department’s Professor Tae-Young Yoon, KAIST, and Biomedical Engineering Institute’s Professor Yeon-Kyun Shin at KIST. KAIST Physics Department’s Professor Yong-Hoon Cho, Ph.D. candidate Do-Yong Lee and KIAS Computational Sciences Department’s Professor Chang-Bong Hyun participated. The research was published on Nature Communications on April 16th.
a) Neurotransmission occurs when vesicles containing neurotransmitters fuse with cell membranes in neuron synapses. A SNARE protein is a cell-membrane fusion protein with a core role of releasing neurotransmitters.
b) A schematic diagram using magnetic nanotweezers to measure protein structure changes on molecular level. The nanotweezers exert an exquisite pull and release of each protein with a force of 1 pN to measure physical changes to nanometer level in real-time to observe the hidden intermediate structure and operation principles of bio-membrane fusion protein.
2013.05.25 View 7120