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High-modulus and strength carbon nanotube fibers using molecular cross-linking
Park, Ok-Kyung,Choi, Hoikil,Jeong, Hanbin,Jung, Yeonsu,Yu, Jaesang,Lee, Jae Kwan,Hwang, Jun Yeon,Kim, Seung Min,Jeong, Youngjin,Park, Chong Rae,Endo, Morinobu,Ku, Bon-Cheol Elsevier 2017 Carbon Vol.118 No.-
<P>We present a systematic and simple approach to produce high-strength carbon nanotube fibers (CNTFs) with electrical conductivity in the high performance range (> 1000 S/cm). We studied several critical parameters to improve the mechanical properties of CNTFs by aryl cross-linking reaction. Both the molecular dynamics (MD) simulations and experimental results showed that the mechanical properties strongly depended on the degree of cross-linking, length of cross-linkers, and CNT diameter. The monobenzene (MB) covalent bonding between CNTF with double-walled CNTs (DWCNTs) showed the highest load transfer, resulting in significantly enhanced specific tensile strength (3.7 N/tex) and Young's modulus (210 N/tex) which are superior to the strongest commercial carbon fiber (3.6 N/tex and 180 N/tex), respectively. Furthermore, the mechanical properties of aryl cross-linked CNTF exhibited no significant change in strength with sample size of CNTFs, showing uniformity of strength with increasing degree of cross-linking. The electrical conductivity of the MB cross-linked CNTFs was similar to 1400 S/cm, which is higher than the best value of commercial carbon fibers (715 S/cm). These results demonstrate that aromatic linker between CNTFs can significantly enhance mechanical properties without significant loss of electrical conductivity. These molecular engineering with MD simulations provide an important route to design and develop ultra-high-performance fibers. (C) 2017 Elsevier Ltd. All rights reserved.</P>
분무패턴 분석을 이용한 가솔린 직접 분사식 인젝터의 개별 분무플럼 분무각 측정 방법에 대한 연구
박정현 ( Jeonghyun Park ),조한빈 ( Hanbin Cho ),박수한 ( Suhan Park ) 한국분무공학회지 2020 한국액체미립화학회지 Vol.25 No.2
The purpose of this study is to propose and compare methods for measuring individual spray cone angles using spray cross-section images. In direct injection gasoline engines, it was believed that the distribution of air-fuel mixture in the combustion chamber directly affected combustion performance and emission formation. However, since gasoline direct injection (GDI) injectors have a small injection angle, interference between individual spray plumes occurs. Therefore, GDI injectors have only measured the spray angle of the entire spray. To overcome these limitations, three methods of indirectly measuring the spray cone angles of individual spray plume were presented and compared by forming sheet beams using Nd:YAG laser and acquiring spray cross-section images. Each method currently has advantages and disadvantages, and research to apply the method suitable for various GDI injectors needs to be continued.
Park, Hye-Kyung,Jeong, Hanbin,Ko, Eunhwa,Lee, Geumwoo,Lee, Ji-Eun,Lee, Sang Kwang,Lee, An-Jung,Im, Jin Young,Hu, Sung,Kim, Seong Heon,Lee, Ji Hoon,Lee, Changwook,Kang, Soosung,Kang, Byoung Heon American Chemical Society 2017 Journal of medicinal chemistry Vol.60 No.17
<P>Although Hsp90 inhibitors can inhibit multiple tumorigenic pathways in cancer cells, their anticancer activity has been disappointingly modest. However, by forcing Hsp90 inhibitors into the mitochondria with mitochondrial delivery vehicles, they were converted into potent drugs targeting the mitochondrial Hsp90 paralog TRAP1. Here, to improve mitochondrial drug accumulation without using the mitochondrial delivery vehicle, we increased freely available drug concentrations in the cytoplasm by reducing the binding of the drugs to the abundant cytoplasmic Hsp90. After analyzing X-ray cocrystal structures, the purine ring of the Hsp90 inhibitor 2 (BIIB021) was modified to pyrazolopyrimidine scaffolds. One pyrazolopyrimidine, 12b (DN401), bound better to TRAP1 than to Hsp90, inactivated the mitochondrial TRAP1 in vivo, and it exhibited potent anticancer activity. Therefore, the rationale and feasible guidelines for developing 12b can potentially be exploited to design a potent TRAP1 inhibitor.</P>
Jeong, Hanbin,Park, Jumi,Jun, Youngsoo,Lee, Changwook National Academy of Sciences 2017 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.114 No.45
<P>The endoplasmic reticulum (ER)-mitochondria encounter structure (ERMES) comprises mitochondrial distribution and morphology 12 (Mdm12), maintenance of mitochondrial morphology 1 (Mmm1), Mdm34, and Mdm10 and mediates physical membrane contact sites and nonvesicular lipid trafficking between the ER and mitochondria in yeast. Herein, we report two crystal structures of the synaptotagmin-like mitochondrial lipid-binding protein (SMP) domain of Mmm1 and the Mdm12-Mmm1 complex at 2.8 angstrom and 3.8 angstrom resolution, respectively. Mmm1 adopts a dimeric SMP structure augmented with two extra structural elements at the N and C termini that are involved in tight self-association and phospholipid coordination. Mmm1 binds two phospholipids inside the hydrophobic cavity, and the phosphate ion of the distal phospholipid is specifically recognized through extensive H-bonds. A positively charged concave surface on the SMP domain not only mediates ER membrane docking but also results in preferential binding to glycerophospholipids such as phosphatidylcholine (PC), phosphatidic acid (PA), phosphatidylglycerol (PG), and phosphatidylserine (PS), some of which are substrates for lipid-modifying enzymes in mitochondria. The Mdm12-Mmm1 structure reveals two Mdm12s binding to the SMP domains of the Mmm1 dimer in a pairwise head-to-tail manner. Direct association of Mmm1 and Mdm12 generates a 210-angstrom-long continuous hydrophobic tunnel that facilitates phospholipid transport. The Mdm12-Mmm1 complex binds all glycerophospholipids except for phosphatidylethanolamine (PE) in vitro.</P>
Mechanistic insight into the nucleus–vacuole junction based on the Vac8p–Nvj1p crystal structure
Jeong, Hanbin,Park, Jumi,Kim, Hye-In,Lee, Miriam,Ko, Young-Joon,Lee, Sanghwa,Jun, Youngsoo,Lee, Changwook National Academy of Sciences 2017 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.114 No.23
<P>Formation of the nucleus-vacuole junction (NVJ) is mediated by direct interaction between the vacuolar protein Vac8p and the outer nuclear endoplasmic reticulum membrane protein Nvj1p. Herein we report the crystal structure of Vac8p bound to Nvj1p at 2.4-angstrom resolution. Vac8p comprises a flexibly connected N-terminal H1 helix followed by 12 armadillo repeats (ARMs) that form a right-handed superhelical structure. The extended 80-angstrom-long loop of Nvj1p specifically binds the highly conserved inner groove formed from ARM1-12 of Vac8p. Disruption of the Nvj1p-Vac8p interaction results in the loss of tight NVJs, which impairs piecemeal microautophagy of the nucleus in Saccharomyces cerevisiae. Vac8p cationic triad (Arg276, Arg317, and Arg359) motifs interacting with Nvj1p are also critical to the recognition of Atg13p, a key component of the cytoplasm-to-vacuole targeting (CVT) pathway, indicating competitive binding to Vac8p. Indeed, mutation of the cationic triad abolishes CVT of Ape1p in vivo. Combined with biochemical data, the crystal structure reveals a Vac8p homodimer formed from ARM1, and this self-association, likely regulated by the flexible H1 helix and the C terminus of Nvj1p, is critical for Vac8p cellular functions.</P>