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Native-like Spider Silk Produced in Metabolically Engineered Bacterium
Microscopic picture of 285 kilodalton recombinant spider silk fiber
Researchers have long envied spiders’ ability to manufacture silk that is light-weighted while as strong and tough as steel or Kevlar. Indeed, finer than human hair, five times stronger by weight than steel, and three times tougher than the top quality man-made fiber Kevlar, spider dragline silk is an ideal material for numerous applications. Suggested industrial applications have ranged from parachute cords and protective clothing to composite materials in aircrafts. Also, many biomedical applications are envisioned due to its biocompatibility and biodegradability.
Unfortunately, natural dragline silk cannot be conveniently obtained by farming spiders because they are highly territorial and aggressive. To develop a more sustainable process, can scientists mass-produce artificial silk while maintaining the amazing properties of native silk? That is something Sang Yup Lee at the Korea Advanced Institute of Science and Technology (KAIST) in Daejeon, the Republic of Korea, and his collaborators, Professor Young Hwan Park at Seoul National University and Professor David Kaplan at Tufts University, wanted to figure out. Their method is very similar to what spiders essentially do: first, expression of recombinant silk proteins; second, making the soluble silk proteins into water-insoluble fibers through spinning.
For the successful expression of high molecular weight spider silk protein, Professor Lee and his colleagues pieced together the silk gene from chemically synthesized oligonucleotides, and then inserted it into the expression host (in this case, an industrially safe bacterium Escherichia coli which is normally found in our gut). Initially, the bacterium refused to the challenging task of producing high molecular weight spider silk protein due to the unique characteristics of the protein, such as extremely large size, repetitive nature of the protein structure, and biased abundance of a particular amino acid glycine. “To make E. coli synthesize this ultra high molecular weight (as big as 285 kilodalton) spider silk protein having highly repetitive amino acid sequence, we helped E. coli overcome the difficulties by systems metabolic engineering,” says Sang Yup Lee, Distinguished Professor of KAIST, who led this project. His team boosted the pool of glycyl-tRNA, the major building block of spider silk protein synthesis. “We could obtain appreciable expression of the 285 kilodalton spider silk protein, which is the largest recombinant silk protein ever produced in E. coli. That was really incredible.” says Dr. Xia.
But this was only step one. The KAIST team performed high-cell-density cultures for mass production of the recombinant spider silk protein. Then, the team developed a simple, easy to scale-up purification process for the recombinant spider silk protein. The purified spider silk protein could be spun into beautiful silk fiber. To study the mechanical properties of the artificial spider silk, the researchers determined tenacity, elongation, and Young’s modulus, the three critical mechanical parameters that represent a fiber’s strength, extensibility, and stiffness. Importantly, the artificial fiber displayed the tenacity, elongation, and Young’s modulus of 508 MPa, 15%, and 21 GPa, respectively, which are comparable to those of the native spider silk.
“We have offered an overall platform for mass production of native-like spider dragline silk. This platform would enable us to have broader industrial and biomedical applications for spider silk. Moreover, many other silk-like biomaterials such as elastin, collagen, byssus, resilin, and other repetitive proteins have similar features to spider silk protein. Thus, our platform should also be useful for their efficient bio-based production and applications,” concludes Professor Lee.
This work is published on July 26 in the Proceedings of the National Academy of Sciences (PNAS) online.
2010.07.28 View 16777 -
Professor Thompson
Professor Mary Kathryn Thompson of Civil and Environmental Engineering Department wrote her regular column on correlation between art and engineering, “Engineers, Artists Not on Opposite Ends.” The column was published by the Korea Herald on July 23, 2010. For reading, please click the link below.
http://www.koreaherald.com/opinion/Detail.jsp?newsMLId=20100722000548
2010.07.23 View 9555 -
The thermal fluctuation and elasticity of cell membranes, lipid vesicles, interacting with pore-forming peptides were reported by a research team at KAIST.
A research team from KAIST, consisted of Sung-Min Choi, Professor of Nuclear and Quantum Engineering Department, and Ji-Hwan Lee, a doctoral student in the Department, published a paper on the “thermal fluctuation and elasticity of lipid vesicles interacting with pore-forming peptides.” The paper was carried by Physical Review Letters, an internationally renowned peer-review journal on physics on July 16, 2010.
Cell membranes, which consist of lipid bilayers, play important roles in cells as barriers to maintain concentrations and matrices to host membrane proteins. During cellular processes such as cell fission and fusion, the cell membranes undergo various morphological changes governed by the interplay between protein and lipid membranes. There have been many theoretical and experimental approaches to understand cellular processes driven by protein-lipid membrane interactions. However, it is not fully established how the membrane elastic properties, which play an important role in membrane deformation, are affected by the protein-membrane interactions.
Antimicrobial peptides are one of the most common examples of proteins that modify membrane morphology. While the pore-forming mechanisms of antimicrobial peptides in lipid bilayers have been widely investigated, there have been only a few attempts to understand the mechanisms in terms of membrane elastic properties. In particular, the effects of pore formation on the membrane fluctuation and elastic properties, which provide key information to understand the mechanism of antimicrobial peptide activity, have not been reported yet. The research team reports the thermal fluctuation and elasticity of lipid vesicles interacting with pore-forming peptides, which were measured by neutron spin-echo spectroscopy.
The results of this study are expected to pay an important role in understanding the elastic behavior and morphological changes of cell membranes induced by protein-membrane interactions, and may provide new insights for developing new theoretical models for membrane fluctuations which include the membrane mediated interaction between protein patches.
(a) (b)
Figure
(a) Schematics for bound melittin and pores in lipid bilayers
(b) P NMR signal ratio (with/without Mn2+) of DOPC LUV-melittin vs P/L at 30˚C. The dashed line is a guide for eyes.
2010.07.23 View 11248 -
The 8th International Conference on Metabolic Engineering was held on June 13-18, 2010 in Jeju Island, South Korea.
From left to right, top row: Distinguished Professor and the conference chair Sang Yup Lee, Sang-Hyup Kim - Secretary to the President of Korea, Dr. Jay Keasling, Dr. Greg Stephanopoulos. Left to right, bottom row: Dr. William Provine, Dr. Terry Papoutsakis, Dr, Jens Nielsen, Dr. Lars Nielsen.
The importance of industrial biotechnology that produces chemicals and materials from renewable biomass is increasing due to climate change and the dearth of natural resources. Industrial biotechnology refers to a technology that allows sustainable bio-based production of chemicals and materials that could enrich human"s lives using microorganisms. This is where metabolic engineering comes into play for successful application of microorganisms, in which they are engineered in our intended way for improved production capability.
The 8th International Conference on Metabolic Engineering, the longest running conference of its kind, was held on June 13-18, 2010 at the International Convention Center in Jeju Island, South Korea. Distinguished Professor Sang Yup Lee of KAIST, Dean of College of Life Science and Bioengineering and Co-Director of Institute for the BioCentury, chaired the conference with the main theme of "metabolic engineering for green growth."
With 300 delegates selected by the committee, papers on production of biofuels, chemicals, biopolymers, and pharmaceutics and the development of fundamental metabolic engineering techniques were presented at the conference along with examples of successful commercialization of products developed by several global companies.
Sang Hyup Kim, Secretary to the President of Korea, gave an opening plenary lecture entitled "Korean green growth initiative," to inform experts from around the globe of the leadership on green growth in Korea. Young Hoon Park, President of Korea Research Institute of Bioscience and Biotechnology (KRIBB, Korea) delivered his congratulatory address.
Sang Hyup Kim said, "Hosting an international conference in Korea on metabolic engineering, which forms a core technology necessary for the development of environmentally friendly processes for producing chemicals and biofuels from renewable biomass, is very meaningful as green growth is a big issue around the globe. This is a great chance to show the excellence of Korea"s green growth associated technology to experts in metabolic engineering and industrial biotechnology."
A total of 47 invited lectures in this conference included recent and important topics, for instance, "Synthetic biology for synthetic fuels" by Dr. Jay Keasling from the Joint BioEnergy Institute (USA), "Microbial oil production from renewable feedstocks" by Dr. Greg Stephanopoulos from MIT (USA), "Yeast as a platform cell factory for production of fuels and chemicals" by Dr. Jens Nielsen from Chalmers University (Sweden), "Mammalian synthetic biology - from tools to therapies" by Dr. Martin Fussengger from ETH (Switzerland), "Building, modeling, and applications of metabolic and transcriptional regulatory networks at a genome-scale" by Dr. Bernhard Palsson from the University of California - San Diego (USA), "Genome analysis and engineering Eschericha coli for sucrose utilization" by Dr. Lars Nielsen from the University of Queensland (Australia), "Artificial microorganisms by synthetic biology" by Dr. Daniel Gibson from JCVI (USA), and "Metabolomics and its applications" by Dr. Masaru Tomita from Keio University (Japan). From Korea, Dr. Jin Hwan Park from the research group of Dr. Sang Yup Lee at KAIST presented "Systems metabolic engineering of Escherichia coli for amino acid production," and Dr. Ji Hyun Kim from KRIBB presented "Genome sequencing and omics systems analysis of the protein cell factory of Escherichia coli".
Global companies involved in biorefinery presented their recent research outcomes with emphasis on commercialized technologies. They included "Metabolic and process engineering for commercial outcomes" by Dr. William Provine from DuPont (USA), "Direct production of 1,4-butanediol from renewable feedstocks" by Dr. Mark Burk from Genomatica (USA), "Development of an economically sustainable bioprocess for the production of bio 1,2-propanediol" by Dr. Francis Voelker from Metabolic Explorer (France), "Biotechnology to the bottom-line: low pH lactic acid production at industrial scale" by Dr. Pirkko Suominen from Cargill (USA), "Bioisoprene™: traditional monomer, traditional chemistry, sustainable source" by Dr. Gregg Whited from Danisco (USA) and "Efficient production of pharmaceuticals by engineered fungi" by Dr. Roel Bovenberg from DSM (Netherlands).
This biennial conference also presented the International Metabolic Engineering Award (expanded version of the previous Merck Metabolic Engineering Award) to the best metabolic engineer in the world. The 2010 International Metabolic Engineering Award went to Dr. E. Terry Papoutsakis from the University of Delaware (USA) who has contributed to the production of biobutanol through the metabolic engineering of Clostridia in the last three decades, and he gave an award lecture. Dr. Sang Yup Lee, the current chair of the upcoming conference, was the previous recipient of this award at the last metabolic engineering conference in 2008.
In addition to the invited lectures, a total of 156 carefully selected poster papers were chosen for presentation, and awards were presented to the best posters after rigorous review by the committee members. Such awards included "The 2010 Metabolic Engineering Best Poster Award" and the "2010 Young Metabolic Engineer Award" from the Metabolic Engineering conference, and prestigious international journal awards, including "Wiley Biotechnology Journal Best Poster Award", "Wiley Biotechnology and Bioengineering Best Poster Award" and "Elsevier Metabolic Engineering Best Paper Award." Dr. Catherine Goodman, a senior editor of Nature Chemical Biology, also presented the "Nature Chemical Biology Best Poster Award on Metabolic Engineering."
Regarding this conference, Dr. Sang Yup Lee, the conference chair, said, "This conference is the best international conference in the field of metabolic engineering, which is held every two years, and Korea is the first Asian country to host it. All the experts and students spend time together from early breakfast to late poster sessions, which is a distinct feature of this conference. Although the number of delegates had typically been limited to 200, around 300 delegates were selected this year to accept more attendees from many people who have been interested in metabolic engineering. Also, it is very fitting that "green growth" is the main topic of this conference because Korea is playing a key role in this field. I"m grateful to the Lotte Scholarship Foundation, COFCO, GS Caltex, Bioneer, US DOE, US NSF, Daesang, CJ Cheiljedang, Genomatica and DuPont who provided us with generous financial support that allowed the successful organization of this conference."
The conference was organized by the Systems Biology Research Project Team supported by the Ministry of Eduction, Science and Technology (MEST), Microbial Frontier Research Project Group, World Class University Project Group at KAIST, Institute for the BioCentury at KAIST, Korean Society for Biotechnology and Bioengineering, and the Engineering Conference International (ECI) of the United States.
Inquiries: Professor Sang Yup Lee (+82-42-350-3930), industrialbio@gmail.com
2010.06.25 View 17869 -
The 6th president of KAIST passed away on May 7, 2010.
Dr. Sang-Soo Lee was the first president of Korea Advanced Institute of Science (KAIS) and the 6th president of KAIST, who died of a chronic disease at the age of 85. The KAIS was the matrix of KAIST today. Graduated from the physics department of Seoul National University in 1949, he later received a doctoral degree in optics from Imperial College of Science and Technology, University of London.
Dr. Lee has greatly contributed to the development of science and technology in Korea in the capacity of a policy administrator, educator, scientist, researcher, and engineer. He held numerous prestigious offices including President of Korea Atomic Energy Research Institute in 1967, of KAIS in 172, and of KAIST in 1989. Dr. Lee also worked as a professor at the physics department of KAIST for 20 years from 1972-1992.
The Society of Photographic Instrumentation Engineers (SPIE), an international society for optics and photonics, was founded in 1955 to advance light-based technologies. Dr. Sang-Soo Lee was a member of the SPIE that issued a news release expressing its sincere condolences to his death. The following is the full text of the news release: http://spie.org/x40527.xml
In memoriam: Sang Soo Lee
10 May 2010
Sang Soo Lee, known as the "Father of Optics" in Korea passed away on May 7, 2010, in Korea. He was 84.
Lee received a B.S. in Physics from Seoul National University in Korea and a Ph.D. from Imperial College of Science and Technology, University of London, UK. Receiving the first Ph.D. in Optics in Korea, Dr. Lee devoted his life to lay the foundation for optical science and engineering for more than four decades as an educator, researcher, and administrator in science policy.
"He was one of the architects of the extraordinary and rapid emergence of Korea as a world leader in science and technology, or perhaps with the rich history of contributions centuries ago, re-emergence would be more appropriate." said Eugene G. Arthurs, SPIE Executive Director.
During his teaching career, Dr. Lee mentored 50 doctoral and more than 100 masters" degree candidates. in the areas of laser physics, wave optics, and quantum optics. Many of his former students have become leaders in academia, government-funded research institutes, and industry both in Korea and abroad. He published more than 250 technical papers and authored five textbooks, including "Wave Optics", "Geometrical Optics", "Quantum Optics", and "Laser Speckles and Holography".
Lee was the first president of the Korea Advanced Institute of Science and Technology (KAIST), and the first president to establish a new government funded graduate school. He played a pivotal role in founding the Optical Society of Korea (OSK) in 1989 and served as its first president.
Lee was an active member of the international scientific community. In addition to his pioneering scholastic achievements at KAIST, he served as the Vice President of the International Commission for Optics (ICO), a Council Member of the Third World Academy of Sciences, and a Council Member of UN University, serving as an ambassador for the optics community, which showed a significant example of how a developing country like Korea can serve international optics community.
Dr. Lee was a Fellow of the International Society for Optical Engineering (SPIE), the Optical Society of America (OSA), and the Korean Physical Society (KPS). He was the recipient of many awards and honors, including the National Order of Civil Merit that is the Presidential Medal of Honor from the Republic of Korea (2000), the Songgok Academic Achievement Prize, the Presidential Award for Science, and the Medal of Honor for Distinguished Scientific Achievement in Korea. In 2006, he was awarded OSA"s Esther Hoffman Beller Medal.
2010.05.19 View 12806 -
Professor Eun-Seong Kim and his research staff observed the phenomena of hysteresis and relaxation dynamics from supersolid Helium
Professor Eun-Seong Kim and his research staff observed the phenomena of hysteresis and relaxation dynamics from supersolid Helium.
Their research paper was published in Nature Physics for the issue of April 2010.
If we take Helium 4 and cool it down at temperatures below 2.176 Kelivin, liquid helium 4 undergoes a phase transition and becomes superfluid with a zero viscosity. The superfluidity was observed in solid helium through an experiment performed by researchers of Pennsylvania State University in 2004. One of the researchers then was Professor Eun-Seong Kim in the Department of Physics, KAIST.
Professor Kim and his research staff, Hyung-Soon Choi, Ph.D., recently published their research results in Nature Physics (April 2010), a highly esteemed journal in the field, on the phenomena of hysteresis and relaxation dynamics observed in supersolid Helium.
For the paper, please download the attached .pdf file.
Nature Physics link: http://www.nature.com
2010.04.13 View 11988 -
New drug targeting method for microbial pathogens developed using in silico cell
A ripple effect is expected on the new antibacterial discovery using “in silico” cells
Featured as a journal cover paper of Molecular BioSystems
A research team of Distinguished Professor Sang Yup Lee at KAIST recently constructed an in silico cell of a microbial pathogen that is resistant to antibiotics and developed a new drug targeting method that could effectively disrupt the pathogen"s growth using the in silico cell.
Hyun Uk Kim, a graduate research assistant at the Department of Chemical and Biomolecular Engineering, KAIST, conducted this study as a part of his thesis research, and the study was featured as a journal cover paper in the February issue of Molecular BioSystems this year, published by The Royal Society of Chemistry based in Europe.
It was relatively easy to treat infectious microbes using antibiotics in the past. However, the overdose of antibiotics has caused pathogens to increase their resistance to various antibiotics, and it has become more difficult to cure infectious diseases these days.
A representative microbial pathogen is Acinetobacter baumannaii. Originally isolated from soils and water, this microorganism did not have resistance to antibiotics, and hence it was easy to eradicate them if infected. However, within a decade, this miroorganism has transformed into a dreadful super-bacterium resistant to antibiotics and caused many casualties among the U.S. and French soldiers who were injured from the recent Iraqi war and infected with Acinetobacter baumannaii.
Professor Lee’s group constructed an in silico cell of this A. baumannii by computationally collecting, integrating, and analyzing the biological information of the bacterium, scattered over various databases and literatures, in order to study this organism"s genomic features and system-wide metabolic characteristics. Furthermore, they employed this in silico cell for integrative approaches, including several network analysis and analysis of essential reactions and metabolites, to predict drug targets that effectively disrupt the pathogen"s growth. Final drug targets are the ones that selectively kill pathogens without harming human body.
Here, essential reactions refer to enzymatic reactions required for normal metabolic functioning in organisms, while essential metabolites indicate chemical compounds required in the metabolism for proper functioning, and their removal brings about the effect of simultaneously disrupting their associated enzymes that interact with them.
This study attempted to predict highly reliable drug targets by systematically scanning biological components, including metabolic genes, enzymatic reactions, that constitute an in silico cell in a short period of time.
This research achievement is highly regarded as it, for the first time, systematically scanned essential metabolites for the effective drug targets using the concept of systems biology, and paved the way for a new antibacterial discovery. This study is also expected to contribute to elucidating the infectious mechanism caused by pathogens.
"Although tons of genomic information is poured in at this moment, application research that efficiently converts this preliminary information into actually useful information is still lagged behind. In this regard, this study is meaningful in that medically useful information is generated from the genomic information of Acinetobacter baumannii," says Professor Lee. "In particular, development of this organism"s in silico cell allows generation of new knowledge regarding essential genes and enzymatic reactions under specific conditions," he added.
This study was supported by the Korean Systems Biology Project of the Ministry of Education, Science and Technology, and the patent for the development of in silico cells of microbial pathogens and drug targeting methods has been filed.
[Picture 1 Cells in silico]
[Picture 2 A process of generating drug targets without harming human body while effectively disrupting the growth of a pathogen, after predicting metabolites from in silico cells]
2010.04.05 View 14671 -
New Text Book on Chemistry Published by KAIST Professor and Student
A chemistry textbook written in English and Korean will aid Korean students to learn General Chemistry in a global academic setting.
Korean students majoring in chemistry and looking for an opportunity to study abroad will have a new, handy textbook that presents them with a practical introduction to an English speaking lecture on general chemistry.
Aiming for advanced Korean high school and college/university students, the inter-language textbook is written by two incumbent professors teaching chemistry at a university in Korea and the US. The book will help Korean students prepare for a classroom where various topics of general chemistry are presented and discussed in English. Clear, collated sections of English and Korean text provide the student with sufficient explanation of the rudimentary topics and concepts.
Composed of 15 chapters on the core subjects of General Chemistry, i.e., Stoichiometry and Chemical Reactions, Thermochemistry, Atomic Structure, and Bonding, the textbook includes essential English vocabulary and usage sections for each chapter; it also contains a pre-reading study guide on the subject that prepares the student for listening to a lecture. This section includes view-graph type slides, audio files, and follow-up questions the student can use to prepare for an English-speaking course. The various accompanying audio files are prepared to expose the student to English scientific dialogue and serve as examples for instruction at Korean secondary and tertiary schools.
The book was coauthored by Korean and American scientists: A father and son, who have taught chemistry at an American and Korean university, wrote the book. Professor Melvyn R. Churchill at the State University of New York at Buffalo and Professor David G. Churchill at KAIST prepared all of the technical English text which was adapted from General Chemistry course lecture notes; the text was further shaped by original perspectives arising from many student interactions and questions.
This English text was translated into Korean by Professor Kwanhee Lee from the Department of Life and Food Science at Handong Global University, who coauthored a previous preparatory book for Korean students in a different subject. He also supplied an important introductory section which serves as a general guide to the classroom student. Kibong Kim, a doctoral student in the Department of Chemistry at KAIST, helped in preparing the book as well.
“This has been definitely a collaborative undertaking with an international academic crew and it underscores that the Korean internationalization in science is mainstream. Professors and a Korean student created a new book for Korean consumption and benefit,” Professor David G. Churchill says.
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Bibliography: “How to Prepare for General Chemistry Taught in English” by David George Churchill, Melvyn Rowen Churchill, Kwanhee Lee & Kibong Kim, Darakwon Publishing, Paju, Republic of Korea, 2010, 400 pp, ISBN 978-89-5995-730-9 (1 Audio CD included)
2010.04.02 View 13518
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Photonic crystals allow the fabrication of miniaturized spectrometers
By Courtesy of Nanowerk
Photonic crystals allow the fabrication of miniaturized spectrometers
(Nanowerk Spotlight) Spectrometers are used in materials analysis by measuring the absorption of light by a surface or chemical substance. These instruments measure properties of light over a specific portion of the electromagnetic spectrum. In conventional spectrometers, a diffraction grating splits the light source into several beams with different propagation directions according to the wavelength of the light. Thus, to achieve sufficient spatial separation for intensity measurements at a small slit, a long light path – i.e., a large instrument – is required.
However, for lab-on-a-chip or microTAS (total analysis system) applications, the spectrometer must be integrated into a sub-centimeter scale device to produce a stand-alone platform. To achieve this, researchers at the Korea Advanced Institute of Science and Technology (KAIST) propose a new paradigm in which the spectrometer is based on an array of photonic crystals with different bandgaps.
"Because photonic crystals refelct light of different wavelengths selectively depending on their bandgaps, we can generate reflected light spanning the entire wavelength range for analysis at different spatial positions using patterned photonic crystals," Seung-Man Yang, Director of the National Creative Research Initiative Center for Intergrated Optofluidic Systems and Professor of the Department of Chemical & Biomolecular Engineering at KAIST, tells Nanowerk. "Therefore, when the light source impinges on the patterned photonic crytals, we can construct the spectrum using the reflection intensity profile from the constituent photonic crystals."
Photonic crystals – also known as photonic band gap material – are similar to semiconductors, only that the electrons are replaced by photons (i.e. light). By creating periodic structures out of materials with contrast in their dielectric constants, it becomes possible to guide the flow of light through the photonic crystals in a way similar to how electrons are directed through doped regions of semiconductors. The photonic band gap (that forbids propagation of a certain frequency range of light) gives rise to distinct optical phenomena and enables one to control light with amazing facility and produce effects that are impossible with conventional optics.
To demonstrate this new concept based on patterned photonic crystals, Yang and his group used non-close-packed colloidal crystals of silica particles dispersed in photocurable resin. Due to the repulsive interparticle potential, monodisperse silica particles spontaneously crystallize into non-close-packed face-centered cubic (fcc) structures at volume fractions above 0.1. Therefore, the particle volume fraction determines both the lattice constant and the bandgap position.
a) Optical image of an ETPTA film containing porous photonic crystal stripe patterns with 20 different bandgaps. b) Reflectance spectra from the 20 strips. c) Optical microscope image of the middle region with the parallel stripe pattern (denoted as white-dotted box in a). d) Cross-sectional SEM images of first, sixth, eleventh and seventeenth strips. The scale bars in a, c and d are 1 cm, 2mm and 2 µm, respectively. (reprinted with permission from Wiley-VCH Verlag)
Reporting their findings in a recent issue of Advanced Materials ("Integration of Colloidal Photonic Crystals toward Miniaturized Spectrometers"), the KAIST team has demonstrated the integration of colloidal photonic crystals with 20 different bandgaps into freestanding films (prepared by soft lithography), and their application as a spectrometer.
Yang explains that the team was able to precisely control the photonic bandgap by varying the particle size and volume fration.
"The prepared colloidal composite structures showed high physical rigidity and chemical resistivity" he says. "The composite structure is suitable for spectroscopic use due to the small full widths at half maximum (FWHMs) of the reflectance spectra, which mean that there is little overlap of the reflectance spectra of neighboring photonic crystal strips."
"On the other hand" says Yang, "porous photonic crystals showed large FWHMs and high reflectivities, which should prove useful in many practical photonic applications that require high optical performance and physical rigidity as well as simple and inexpensive preparation."
In addition to fabricating miniaturized spectrometers, which can for instance be integrated into small lab-on-a-chip devices, these integrated photonic crystals can be potentially used for tunable band reflection mirrors, optical switches, and tunable lasing cavities. Moreover, patterned photonic crystals with RGB colors are well-suited for use in reflection-mode microdisplay devices.
Yang points out that, although the spectrometric resolution can be reduced by employing the smaller bandgap interval and photonic bandwidth, there is a limitation. "Now, we are studying photonic crystals with continuous modulation of bandgap position. We expect that the photonic crystals can reduce the resolution to 0.01 nm."
By Michael Berger. Copyright 2010 Nanowerk
2010.03.17 View 13098
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Opening Ceremony Held on February 3, 2010 for Intellectual Property Training Center
KAIST Opened Training Center for Young Entrepreneurs
Commissioner Jung-Sik Koh of Korean Intellectual Property Office (KIPO) and KAIST faculty members including Soon-Hong Jang, Vice President of Operations and Kwang-Hyung Lee, Dean of Academic Affairs Office, joined an opening ceremony held on February 3rd, 2010 to launch a training center for the next generation entrepreneurs who will lead the intellectual property (IP) industry in Korea.
The training center was built in cooperation with KIPO to educate and support young entrepreneurs and prepare them to become tomorrow’s IP business leaders like Bill Gates of Microsoft and Google’s founders, Larry Page and Sergey Brin.
Going through a vigorous selection process, a total of 101 students (51 for intermediate and 50 for advanced level) were chosen last December for an orientation program that will begin February 3rd and continue through February 5th. In addition to the training center at KAIST, KIPO supported to launch another training center at the Pohang University of Science and Technology (POSTECH), which has been up and running since January 27th, 2010.
2010.02.04 View 12560 -
Prof. Lee"s Team Succeeds in Producing Plastics Without Use of Fossil Fuels
A team of scientists led by Prof. Sang-Yup Lee of the Department of Biological Sciences at KAIST have succeeded in producing the polymers used for everyday plastics through bioengineering, rather than through the use of fossil fuel based chemicals, the university authorities said on Tuesday (Nov. 24).
This groundbreaking research, which may now allow for the production of environmentally conscious plastics, has been published in two papers in the journal Biotechnology and Bioengineering.
Polymers are molecules found in everyday life in the form of plastics and rubbers. The team consisted of scientists from KAIST and Korean chemical company LG Chem focused their research on polylactic acid (PLA), a bio-based polymer which holds the key to producing plastics through natural and renewable resources.
"The polyesters and other polymers we use everyday are mostly derived from fossil oils made through the refinery or chemical process," said Lee. "The idea of producing polymers from renewable biomass has attracted much attention due to the increasing concerns of environmental problems and the limited nature of fossil resources. PLA is considered a good alternative to petroleum based plastics as it is both biodegradable and has a low toxicity to humans."
Until now PLA has been produced in a two-step fermentation and chemical process of polymerization, which is both complex and expensive. Now, through the use of a metabolically engineered strain of E.coli, the team has developed a one-stage process which produces polylactic acid and its copolymers through direct fermentation. This makes the renewable production of PLA and lactate-containing copolymers cheaper and more commercially viable.
"By developing a strategy which combines metabolic engineering and enzyme engineering, we"ve developed an efficient bio-based one-step production process for PLA and its copolymers," said Lee. "This means that a developed E. coli strain is now capable of efficiently producing unnatural polymers, through a one-step fermentation process,"
This combined approach of systems-level metabolic engineering and enzyme engineering now allows for the production of polymer and polyester based products through direct microbial fermentation of renewable resources.
"Global warming and other environmental problems are urging us to develop sustainable processes based on renewable resources," concluded Lee. "This new strategy should be generally useful for developing other engineered organisms capable of producing various unnatural polymers by direct fermentation from renewable resources".
2009.11.30 View 13914 -
Prof. Sang-Yup Lee Founding Member of Board of Editors of mBop
Prof. Sang-Yup Lee of the Department of Chemical and Biomolecular Engineering at KAIST has been appointed as one of the founding board of editors of the mBio which will be launched next year, the university reported on Friday (Nov. 20).
mBio is the American Society for Microbiology"s first all-online, open access journal which will be launched in next May. According to the mBio website, the journal"s scope "will reflect the enormity of the microbial world, a highly interconnected biosphere where microbes interact with living and non-living matter to produce outcomes that range from symbiosis to pathogenesis, energy acquisition and conversion, climate change, geologic change, food and drug production, and even animal behavioral change."
Prof. Lee, LG Chem Chair Professor, is currently the Dean of the College of Life Science and Bioengineering and director of the Center for Systems and Synthetic Biotechnology. He received his B.S. in Chemical Engineering from Seoul National Univeristy in Korea and his M.S. and Ph.D. in Chemical Engineering from Northwestern University.
As of September 2009, he has published 298 journal papers and has more than 440 patents either registered or applied. Also, he has published 47 books/book chapters, "Systems Biology and Biotechnology of Escherichia Coli" being the latest.
His research interests are systems biology and biotechnology, industrial biotechnology, metabolic engineering, synthetic biology and nanobiotechnology. In particular, he has pioneered systems metabolic engineering, which integrates systems biology with metabolic engineering, for the development of micropoganisms possessing superior properties for industrial applications.
2009.11.20 View 11642