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Lee, Hyosun,Nedrygailov, Ievgen I.,Lee, Young Keun,Lee, Changhwan,Choi, Hongkyw,Choi, Jin Sik,Choi, Choon-Gi,Park, Jeong Young American Chemical Society 2016 NANO LETTERS Vol.16 No.3
<P>Direct detection of hot electrons generated by exothermic surface reactions on nanocatalysts is an effective strategy to obtain insight into electronic excitation during chemical reactions. For this purpose, we fabricated a novel catalytic nanodiode based on a Schottky junction between a single layer of graphene and an n-type TiO2 layer that enables the detection of hot electron flows produced by hydrogen oxidation on Pt nanoparticles. By making a comparative analysis of data obtained from measuring the hot electron current (chemicurrent) and turnover frequency, we demonstrate that graphene's unique electronic structure and extraordinary material properties, including its atomically thin nature and ballistic electron transport, allow improved conductivity at the interface between the catalytic Pt nanoparticles and the support. Thereby, graphene-based nanodiodes offer an effective and facile way to approach the study of chemical energy conversion mechanisms in composite catalysts with carbon-based supports.</P>
Lee, Changsun,Shim, Sehwan,Jang, Hyosun,Myung, Hyunwook,Lee, Janet,Bae, Chang-Hwan,Myung, Jae Kyung,Kim, Min-Jung,Lee, Seung Bum,Jang, Won-Suk,Lee, Sun-Joo,Kim, Hwi-Yool,Lee, Seung-Sook,Park, Sunhoo Elsevier 2017 cytotherapy Vol.19 No.9
<P>Background aims. Mesenchymal stromal cells (MSCs) are a promising agent for treating impaired wound healing, and their therapeutic potential may be enhanced by employing extracellular matrix scaffolds as cell culture scaffolds or transplant cell carriers. Here, we evaluated the effect of human umbilical cord blood derived (hUCB)-MSCs and a porcine small intestinal submucosa (SIS)-derived extracellular matrix scaffold in a combined radiation-wound mouse model of impaired wound healing. Methods. hUCB-MSCs and SIS hydrogel composite was applied to the excisional wound of whole-body irradiated mice. Assessment of wound closing and histological evaluation were performed in vivo. We also cultured hUCB-MSCs on SIS gel and examined the angiogenic effect of conditioned medium on irradiated human umbilical vein endothelial cells (HUVECs) in vitro. Results. hUCB-MSCs and SIS hydrogel composite treatment enhanced wound healing and angiogenesis in the wound site of mice. Conditioned medium from hUCB-MSCs cultured on SIS hydrogel promoted the chemotaxis of irradiated HUVECs more than their proliferation. The secretion of angiogenic growth factors hepatocyte growth factor, vascular endothelial growth factor-A and angiopoietin-1 from hUCB-MSCs was significantly increased by SIS hydrogel, with HGF being the predominant angiogenic factor Of irradiated HUVECs. Conclusions. Our results suggest that the wound healing effect of hUCB-MSCs is enhanced by SIS hydrogel via a paracrine factor-mediated recruitment of vascular endothelial cells in a combined radiation-wound mouse model.</P>
Lee, Jaegyeong,Lee, Hyosun,Nayab, Saira,Yoon, Keun Byoung Elsevier 2019 Polyhedron Vol.158 No.-
<P><B>Abstract</B></P> <P>The reaction of <B>[CdBr<SUB>2</SUB>·4H<SUB>2</SUB>O]</B> with <I>N</I> <SUP>1</SUP>,<I>N</I> <SUP>1</SUP>-dimethyl-<I>N</I> <SUP>2</SUP>-(pyridin-2-ylmethylene)ethane-1,2-diamine) (<B>L<SUB>A</SUB> </B>), 2-methoxy-<I>N</I>-(pyridin-2-ylmethylene)ethanamine (<B>L<SUB>B</SUB> </B>), 2-(piperidin-1-yl)-<I>N</I>-(pyridin-2-ylmethylene)ethanamine (<B>L<SUB>C</SUB> </B>), 2-morpholino-<I>N</I>-(pyridin-2-ylmethylene)ethanamine (<B>L<SUB>D</SUB> </B>), <I>N</I> <SUP>1</SUP>,<I>N</I> <SUP>1</SUP>-dimethyl-<I>N</I> <SUP>3</SUP>-(pyridin-2-ylmethylene)propane-1,3-diamine (<B>L<SUB>E</SUB> </B>) and 3-methoxy-<I>N</I>-(pyridin-2-ylmethylene)propan-1-amine (<B>L<SUB>F</SUB> </B>) in methanol produced the tridentate <B>[(<I>NN</I>′<I>X</I>)CdBr<SUB>2</SUB>]</B> complexes, namely <B>[L<SUB>A</SUB>CdBr<SUB>2</SUB>]</B>, <B>[L<SUB>B</SUB>CdBr<SUB>2</SUB>]</B>, <B>[L<SUB>C</SUB>CdBr<SUB>2</SUB>]</B>, <B>[L<SUB>D</SUB>CdBr<SUB>2</SUB>]</B>, <B>[L<SUB>E</SUB>CdBr<SUB>2</SUB>]</B> and <B>[L<SUB>F</SUB>CdBr<SUB>2</SUB>]</B>, respectively. The molecular structures of the Cd(II) complexes revealed that the cadmium atom in <B>[L<SUB>n</SUB>CdBr<SUB>2</SUB>]</B> (L<SUB>n</SUB> = L<SUB>A</SUB>, L<SUB>C</SUB>-L<SUB>E</SUB>) has a distorted square pyramidal geometry involving two nitrogen atoms and one nitrogen or oxygen atom of the <I>N,N</I>′<I>,X</I>-tridentate ligands and two bromo ligands. The dimethyl derivatives, generated <I>in situ</I>, <B>[L<SUB>n</SUB>CdMe<SUB>2</SUB>]</B> (L<SUB>A</SUB>-L<SUB>F</SUB>) initiated the polymerisation of <I>rac</I>-Lactide (<I>rac</I>-LA) and yielded heterotactic PLA. Notably, the substituent attached to ligand architecture affects the activities towards the <I>rac</I>-LA polymerisation, whereas the stereoselectivities remained unchanged. Moderate activities towards the polymerisation of methylmethacrylate (MMA) polymerisation in the presence of modified methylaluminoxane (MMAO) at 60 °C were observed for <B>[L<SUB>n</SUB>CdBr<SUB>2</SUB>]</B> (L<SUB>A</SUB>-L<SUB>F</SUB>). The preliminary results showed that these complexes yielded syndio-rich poly(methylmethacrylate) (PMMA) ([<I>rr</I>] = 0.66).</P> <P><B>Graphical abstract</B></P> <P>Cadmium(II) complexes <B>[L<SUB>n</SUB>CdCl<SUB>2</SUB>]</B> (L<SUB>n</SUB> = L<SUB>A</SUB>-L<SUB>F</SUB>) bearing <I>N</I>,<I>N</I>′,<I>X</I>-substituted 2-iminomethylpyridine ligands have been synthesized and characterized. The dimethyl derivatives, generated <I>in situ</I> from the synthesised complexes, polymerized the stereoselective ROP of <I>rac</I>-LA and yielded heterotactic PLA. Further, the Cd(II) complexes initiate MMA polymerisation in the presence of MMAO, yielding syndio-enriched PMMA. The substituents attached to the <I>X</I>-donor atom of the iminomethylpyridine ligands affected the catalytic activity, whereas the stereoselectivity remained unchanged.</P> <P>[DISPLAY OMISSION]</P>
Enhanced Surface Plasmon Effect of Ag/TiO<sub>2</sub> Nanodiodes on Internal Photoemission
Lee, Hyosun,Lee, Young Keun,Hwang, Euyheon,Park, Jeong Young American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.11
<P>Over the last several decades, innovative light-harvesting devices have evolved to achieve high-efficiency solar energy transfer. Understanding the mechanism of plasmon resonance is very desirable to overcome the conventional efficiency limits of photovoltaics. The influence of localized surface plasmon resonance on hot electron flow at a metal–semiconductor interface was observed with a Schottky diode composed of a thin silver layer on TiO<SUB>2</SUB>; subsequent X-ray photoelectron spectroscopy characterized how oxygen in the Ag/TiO<SUB>2</SUB> nanodiode influenced the Schottky barrier height. Photoexcited electrons generate photocurrent when they have enough energy to travel over the Schottky barrier formed at the metal–semiconductor interface. We observed that the photocurrent could be enhanced by optically excited surface plasmons. When the surface plasmons are excited on the corrugated Ag metal surface, they decay into energetic hot electron–hole pairs, contributing to the total photocurrent. The abnormal resonance peaks observed in the incident photons to current conversion efficiency can be attributed to surface plasmon effects. We observed that photocurrent enhancement due to surface plasmons was closely related to the corrugation (or roughness) of the metal surface. While the photocurrent measured on Ag/TiO<SUB>2</SUB> exhibits surface plasmon peaks, the photocurrent on Au/TiO<SUB>2</SUB> does not show any peaks even at the Au surface plasmon energy frequency presumably because of the smoothness of the gold film. We modified the thickness and morphology of a continuous Ag layer using electron beam evaporation deposition and heating under gas conditions and found that morphological changes and the thickness of the Ag film are key factors in controlling the internal photoemission efficiency.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-11/jp409894b/production/images/medium/jp-2013-09894b_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp409894b'>ACS Electronic Supporting Info</A></P>
Sinomonas terrae sp. nov., Isolated from an Agricultural Soil
( Hyosun Lee ),( Ji Yeon Han ),( Dong-uk Kim ) 한국미생물생명공학회 2023 Journal of microbiology and biotechnology Vol.33 No.7
While searching for the bacteria which are responsible for degradation of pesticide in soybean field soil, a novel bacterial strain, designated 5-5T, was isolated. The cells of the strain were Gramstaining- positive, aerobic and non-motile rods. Growth occurred at 10-42℃ (optimum, 30℃), pH 5.5- 9.0 (optimum, pH 7.0-7.5), and 0-2% (w/v) NaCl (optimum, 1%). The predominant fatty acids were C<sub>15:0</sub> anteiso, C<sub>17:0</sub> anteiso, and summed feature 8 (C<sub>18:1</sub> ω7c and/or C<sub>18:1</sub> ω6c). The predominant menaquinone was MK-9 (H<sub>2</sub>). Diphosphatidylglycerol, glycolipids, phosphatidylinositol, and phosphatidylglycerol were the major polar lipids. Phylogenetic analysis of 16S rRNA gene sequences indicated that strain 5-5<sup>T</sup> is a member of the genus Sinomonas and its closest relative is Sinomonas humi MUSC 117<sup>T</sup>, sharing a genetic similarity of 98.4%. The draft genome of strain 5-5<sup>T</sup> was 4,727,205 bp long with an N50 contig of 4,464,284 bp. Genomic DNA G+C content of strain 5-5<sup>T</sup> was 68.0 mol%. The average nucleotide identity (ANI) values between strain 5-5<sup>T</sup> and its closest strains S. humi MUSC 117<sup>T</sup> and S. susongensis A31<sup>T</sup> were 87.0, and 84.3 % respectively. In silico DNA-DNA hybridization values between strain 5-5<sup>T</sup> and its closest strains S. humi MUSC 117<sup>T</sup> and S. susongensis A31<sup>T</sup> were 32.5% and 27.9% respectively. Based on the ANI and in silico DNA-DNA hybridization analyses, the 5- 5<sup>T</sup> strain was considered as novel species belonging to the genus Sinomonas. On the basis of the results from phenotypic, genotypic and chemotaxonomic analyses, strain 5-5<sup>T</sup> represents a novel species of the genus Sinomonas, for which the name Sinomonas terrae sp. nov. is proposed. The type strain is 5-5<sup>T</sup> (=KCTC 49650<sup>T</sup>=NBRC 115790<sup>T</sup>).