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MFAML: a standard data structure for representing and exchanging metabolic flux models
Yun, Hongseok,Lee, Dong-Yup,Jeong, Joonwoo,Lee, Seunghyun,Lee, Sang Yup Oxford University Press 2005 Bioinformatics Vol.21 No.15
<P><B>Summary:</B> MFAML is a standard data structure designed for the formal representation and effective exchange of metabolic flux models. It allows for the explicit description of stationary states of a metabolic system by defining environmental/genetic conditions of the system, e.g. flux measurements, balancing constraints and physiological objectives as well as basic information on metabolites and reactions. In addition, a library of MFAML comprising a model parser and a converter provides an open framework for establishing the pipeline from metabolic modeling to metabolic flux analysis.</P><P><B>Availability:</B> MFAML (version 1) is fully described and available at http://mbel.kaist.ac.kr/mfaml/</P><P><B>Contact:</B>leesy@kaist.ac.kr</P>
Yun, Yang Sik,Park, Hongseok,Yun, Danim,Song, Chyan Kyung,Kim, Tae Yong,Lee, Kyung Rok,Kim, Younhwa,Han, Jeong Woo,Yi, Jongheop The Royal Society of Chemistry 2018 Chemical communications Vol.54 No.52
<P>Catalytic activity was efficiently tuned <I>via</I> manipulating the electronic state of a catalyst, induced by a facile doping method in a metal/graphene system. The strategy was proven to be applicable to not only transition metal but also noble metal catalysts in CO hydrogenation and 4-nitrophenol reduction.</P>
Hongseok Yun(윤홍석),권승호,김범준 한국고분자학회 2021 한국고분자학회 학술대회 연구논문 초록집 Vol.46 No.2
We present the light-driven active shapeshifting of block copolymer (BCP) particles. The key strategy is the design of azobenzene-grafted Au nanoparticles (Au@Azo NPs) as light-responsive surfactants through photoisomerization of azobenzene ligands. In this way, visible light induced formation of onion-like spherical polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) BCP particles due to the non-polar nature of trans-Azo ligands, while the UV-induced isomerization to polar cis-Azo isomers caused transformation of the spheres to ellipsoidal BCP particles. This light-driven shape change was fully reversible over multiple cycles of irradiation with UV/Vis light. The shape evolution process was captured using a cryogenic electron microscope. Finally, light-dependent fluorescence of these hybrid BCP particles was successfully demonstrated, translating the change in particle shape into an optical signal.
Symmetry Transitions of Polymer-Grafted Nanoparticles: Grafting Density Effect
Yun, Hongseok,Yu, Ji Woong,Lee, Young Jun,Kim, Jin-Seong,Park, Chan Ho,Nam, Chongyong,Han, Junghun,Heo, Tae-Young,Choi, Soo-Hyung,Lee, Doh C.,Lee, Won Bo,Stein, Gila E.,Kim, Bumjoon J. American Chemical Society 2019 Chemistry of materials Vol.31 No.14
<P>We examined the packing structure of polystyrene-coated gold nanoparticles (Au@PS) as a function of grafting density. A series of Au@PS nanoparticles with grafting densities in the range of 0.51-1.94 chains nm<SUP>-2</SUP> were prepared by a ligand exchange process using thiol-terminated PS and then self-assembled at a liquid-air interface. We observed a transition from disordered to body-centered cubic (bcc) to face-centered cubic (fcc) arrangements with increasing grafting density, even though the ligand length-to-core radius ratio (λ) was as high as 3.0, a condition that typically favors nonclose-packed bcc symmetry in the self-assembly of hard nanoparticles. To explain this phenomenon, we define λ<SUB>eff</SUB> to include the concentrated polymer brush regime as part of the “hard core”, which predicts that the softness of Au@PS nanoparticles is reduced from 1.53 to 0.14 in a theta solvent as the grafting density increases from 0.51 to 1.94 chains nm<SUP>-2</SUP>. This new definition of λ can also predict the effective radii of nanoparticles using the established optimal packing model. The experimental findings are supported by a combination of coarse-grained molecular dynamics simulation and adaptive common neighbor analysis, which show that changes in grafting density can drive the observed transitions in nanoparticle packing. These studies provide new insights for controlling the self-assembled symmetries of polymer-coated nanocrystals using a simple ligand exchange process to tune particle softness.</P> [FIG OMISSION]</BR>
Yun, Yang Sik,Lee, Minzae,Sung, Jongbaek,Yun, Danim,Kim, Tae Yong,Park, Hongseok,Lee, Kyung Rok,Song, Chyan Kyung,Kim, Younhwa,Lee, Joongwon,Seo, Young-Jong,Song, In Kyu,Yi, Jongheop Elsevier 2018 Applied Catalysis B Vol.237 No.-
<P><B>Abstract</B></P> <P>Ce-incorporated MoVTeNbO catalysts were developed to enhance ethylene productivity of oxidative dehydrogenation of ethane (ODHE) to ethylene. Structural characterizations (XRD, TEM, STEM, Raman, and UV–vis DRS) and DFT calculations revealed that Ce atoms were incorporated into MoVTeNbO framework with maintaining its unique structure (<I>M1</I> phase), which is active phase for ODHE. The reducibility of the catalysts was enhanced and both V<SUP>5+</SUP> and the lattice oxygen species available to ODHE reaction were enriched by incorporation of Ce, confirmed by TPR, XPS, and pulse injection method, respectively. These improved properties enhanced the conversion of ethane while maintaining their excellent selectivity to ethylene for MoVTeNbCeO catalysts. It is noteworthy that 56.2% of ethane conversion and 95.4% of ethylene selectivity were retained for 200 h over MoVTeNbCeO-0.1 catalyst. Ethylene productivity was calculated to be 1.11 kgC<SUB>2</SUB>H<SUB>4</SUB>/kg<SUB>cat</SUB> h. The developed catalyst exhibits substantial level of ethylene productivity and stability having the possibility with low production of CO<SUB>x</SUB> to make a step forward for industrialization of oxidative dehydrogenation of ethane.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ce incorporated MoVTeNbO catalyst is synthesized by hydrothermal method. </LI> <LI> Various characterizations and DFT calculations prove incorporation of Ce. </LI> <LI> Incorporated Ce induces enrichments in fraction of V<SUP>5+</SUP> and lattice oxygen capacity. </LI> <LI> Enhanced catalytic activity was observed by incorporated Ce than catalyst without Ce. </LI> <LI> MoVTeNbCeO-0.1 shows excellent ethylene productivity and selectivity with stability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>