• Title/Summary/Keyword: Hydrogen center

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Crystal Structure of a Highly Thermostable α-Carbonic Anhydrase from Persephonella marina EX-H1

  • Kim, Subin;Sung, Jongmin;Yeon, Jungyoon;Choi, Seung Hun;Jin, Mi Sun
    • Molecules and Cells
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    • v.42 no.6
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    • pp.460-469
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    • 2019
  • Bacterial ${\alpha}-type$ carbonic anhydrase (${\alpha}-CA$) is a zinc metalloenzyme that catalyzes the reversible and extremely rapid interconversion of carbon dioxide to bicarbonate. In this study, we report the first crystal structure of a hyperthermostable ${\alpha}-CA$ from Persephonella marina EX-H1 (pmCA) in the absence and presence of competitive inhibitor, acetazolamide. The structure reveals a compactly folded pmCA homodimer in which each monomer consists of a 10-stranded ${\beta}-sheet$ in the center. The catalytic zinc ion is coordinated by three highly conserved histidine residues with an exchangeable fourth ligand (a water molecule, a bicarbonate anion, or the sulfonamide group of acetazolamide). Together with an intramolecular disulfide bond, extensive interfacial networks of hydrogen bonds, ionic and hydrophobic interactions stabilize the dimeric structure and are likely responsible for the high thermal stability. We also identified novel binding sites for calcium ions at the crystallographic interface, which serve as molecular glue linking negatively charged and otherwise repulsive surfaces. Furthermore, this large negatively charged patch appears to further increase the thermostability at alkaline pH range via favorable charge-charge interactions between pmCA and solvent molecules. These findings may assist development of novel ${\alpha}-CAs$ with improved thermal and/or alkaline stability for applications such as $CO_2$ capture and sequestration.

Anthocyanins from Hibiscus syriacus L. Inhibit Oxidative Stress-mediated Apoptosis by Activating the Nrf2/HO-1 Signaling Pathway

  • Molagoda, Ilandarage Menu Neelaka;Karunarathne, Wisurumuni Arachchilage Hasitha Maduranga;Lee, Kyoung Tae;Choi, Yung Hyun;Jayasooriya, Rajapaksha Gedara Prasad Tharanga;Kim, Gi-Young
    • Proceedings of the Plant Resources Society of Korea Conference
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    • 2019.10a
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    • pp.91-91
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    • 2019
  • Hibiscus syriacus L. is widely distributed throughout Eastern and Southern Asia and its root bark has been used as a traditional remedy. Recently, the extracts of H. syriacus L. exerts anti-cancerous, anti-microbial, and anti-inflammatory activities. However, the effect of anthocyanin-rich fraction of H. syriacus L. petals (PS) has not been studied under excessive oxidative stress. In this study, we evaluated the cellular protective effect of PS in HaCaT human skin keratinocytes under hydrogen peroxide ($H_2O_2$)-induced oxidative stress conditions. PS at below $400{\mu}g/ml$ did not show any cell death; however, over $800{\mu}g/ml$ of PS gradually increased cell death. PS at below $400{\mu}g/ml$ significantly inhibited $H_2O_2$-induced apoptosis in HaCaT cells concomitant with downregulation of Bax and upregulation of pro-PARP and p-Bcl-2. Additionally, PS remarkably reversed $H_2O_2$-induced excessive reactive oxygen species (ROS) production and apoptosis, and also significantly inhibited mitochondrial ROS production concomitant with suppression of $H_2O_2$-induced mitochondrial depolarization. $H_2O_2$-mediated ratio of Bax to Bcl-2, and caspase-3 activation were markedly abolished in the presence of PS. Moreover, the inhibition of HO-1 function using zinc protoporphyrin, an HO-1 inhibitor, significantly attenuated the cellular protective effects of PS against $H_2O_2$, indicating the significance of HO-1 in PS mediated cytoprotective effect, which was mediated by activating nuclear factor erythroid 2-related factor-2 (Nrf2). Taken together, our results suggest that cytoprotective effect of PS in HaCaT keratinocytes against oxidative stress-induced apoptosis is mediated by inhibiting cellular and mitochondrial ROS production, which is downregulated by activating Nrf2/HO-1 axis.

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Structure of a Copper(Ⅱ) Hexaazamacrotricyclic Complex : (1,3,6,9,11,14-Hexaazatricyclo[12.2.1.16,9]octadecane)-copper(Ⅱ) Perchlorate

  • Cheon Manseog;Suh Paik Myunghyun;Shin Whanchul
    • Bulletin of the Korean Chemical Society
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    • v.13 no.4
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    • pp.363-367
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    • 1992
  • The crystal structure of (1,3,6,9,11,14-hexaazatricycol[12.2.1.$1^{6,9}$]octadecane)copper(Ⅱ) perchlorate, Cu($C_{12}H_{26}N_6$)$(ClO_4)_2$, has been determined by the X-ray diffraction methods. The crystal data are as follows: Mr=516.9, triclinic, ${\alpha}=8.572\;(2)$, b=8.499 (3), c=15.204 (3) ${\AA}$, ${\alpha}=80.42\;(5),\;{\beta}=73.57\;(3),\;{\gamma}=69.82\;(4)^{\circ},\;V=994.2\;{\AA}^3,\;D_C=1.726\;gcm^{-3}$, space group $P{\tilde{1}},\;Z=2,\;{\mu}=21.27\;cm^{-1}&, F(000)=534 and T=297 K. The structure was solved by direct methods and refined by full-matrix least-squares methods to and R value of 0.081 for 1608 observed reflections measured with graphite-mono-chromated Mo Ka radiation on a diffractometer. There are two independent complexes in the unit cell. The two copper ions lie at the special positions (1/2, 0, 0) and (0, 1/2, 1/2)and each complex possesses crystallographic center of symmetry. Each Cu ion is coordinated to four nitrogen donors if the hexaazamacrotricyclic ligand and weakly interacts with two oxygen atoms of the perchlorate ions to form a tetragonally distorted octahedral coordination geometry. The Cu_N (sec), Cu_N(tert) and Cu_O coordination distances are 1.985 (14), 2.055 (14) and 2.757 (13) ${\AA}$ for the complex A and 1.996 (10), 2.040 (11) and 2.660 (13) ${\AA}$ for the complex B, respectively. The macrocycles in the two independent cations assume a similar conformation with the average r.m.s. deviation of 0.073 ${\AA}$. Two 1,3-diazacyclopentane ring moieties of the hexaazamacrotricyclic ligand are placed oppositely and almost perpendicularly to the square coordination plane of the ruffled 14-membered macrocycle. The secondary N atoms are hydrogen-bonded to the perchlorate O atoms with distances of 3.017 (23) and 3.025 (19) ${\AA}$ for the complexes A and B, respectively.

Effect of Tert-Butyl Alcohol Template on the Pore Structure of Porous Tungsten in Freeze Drying Process (동결건조 공정에서 Tert-butyl alcohol 기공형성제가 텅스텐 다공체의 기공구조에 미치는 영향)

  • Lee, Eui Seon;Heo, Youn Ji;Ko, Yun Taek;Park, Jin Gyeong;Cho, Yong-Ho;Oh, Sung-Tag
    • Journal of Powder Materials
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    • v.28 no.3
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    • pp.216-220
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    • 2021
  • The effect of tert-butyl alcohol (TBA) as a freezing solvent on the pore structure of a porous tungsten body prepared by freeze-drying is analyzed. TBA slurries with a WO3 content of 10 vol% are prepared by mixing with a small amount of dispersant and binder at 30℃. The slurries are frozen at -25℃, and pores are formed in the frozen specimens by the sublimation of TBA during drying in air. After hydrogen reduction at 800℃ and sintering at 1000℃, the green body of WO3 is completely converted to porous W with various pore structures. Directional pores from the center of the specimen to the outside are observed in the sintered bodies because of the columnar growth of TBA. A decrease in pore directionality and porosity is observed in the specimens prepared by long-duration drying and sintering. The change in pore structure is explained by the growth of the freezing solvent and densification.

FBR CFD Simulation of Steam Methanol Reforming Reaction using Intrinsic Kinetic Data of Copper-impregnated Hydrotalcite Catalyst (구리가 함침된 하이드로탈사이트 촉매의 고유 키네틱 데이터를 이용한 메탄올 수증기 개질반응의 고정층 반응기 CFD 시뮬레이션)

  • Jae-hyeok Lee;Dongil Shin;Ho-Geun Ahn
    • Journal of the Korean Institute of Gas
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    • v.27 no.1
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    • pp.78-85
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    • 2023
  • Fixed-bed reactor Computational Fluid Dynamics (CFD) simulation of methanol steam reforming reaction was performed using the intrinsic kinetic data of the copper-impregnated hydrotalcite catalyst. The activation energy of the copper hydrotalcite catalyst obtained from the previous study results was 97.4 kJ/mol, and the pre-exponential was 5.904 × 1010. Process simulation was performed using the calculated values and showed a similar tendency to the experimental results. And the conversion rate according to the change of the reaction temperature (200 - 450 ℃) and the molar ratio of methanol and water was observed using the intrinsic kinetic data. In addition, mass and heat transfer phenomena analysis of a commercial reactor (I.D. 0.05 - 0.1m, Length 1m) was predicted through axial 2D Symmetry simulation using the power law model of the above kinetic constants.

A Study on Effects of Climate Technology Workforce Development Program (기후기술 인재양성사업의 효과성 연구)

  • Da-Eun Kim;Yong-Woon Chung;Jong-Wook Sohn;Eun-Sun Jeong
    • Industry Promotion Research
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    • v.8 no.2
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    • pp.45-59
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    • 2023
  • In response to the increasing global competition for technological supremacy to address climate change, it is crucial to develop workforce development programs in the field of climate technology to accumulate the national technological capabilities. However, these programs are rarely monitored and evaluated, and research related to monitoring and evaluation in the field of climate technology workforce development is limited. Therefore, this study aimed to investigate the impact of workforce development programs in hydrogen energy and policy sectors on students' R&D capabilities and career aspirations in these sectors. The survey and focus group interviews with beneficiaries revealed that individual students' R&D capabilities and career confidence improved, and group-level R&D capabilities were also enhanced, and students felt greater appreciation on the significance of climate technology. The results of this study suggest that the necessary R&D capabilities to train R&D workforce in climate technology have been developed, but more measures are required to promote career development in this field.

Fabrication of IZO thin films for flexible organic light emitting diodes by RF magnetron sputtering

  • Jun, D.G.;Cho, H.H.;Jo, D.B.;Lee, K.M.
    • Journal of Ceramic Processing Research
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    • v.13 no.spc2
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    • pp.260-264
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    • 2012
  • We have investigated the effect of ambient gases on the structural, electrical, and optical characteristics of IZO thin films intended for use as anode contacts in the organic light emitting diodes (OLED) devices. These IZO thin films were deposited on the PES film by radio frequency (RF) magnetron sputtering under different ambient gases (Ar, Ar + O2, and Ar + H2) at room temperature. In order to investigate the influences of the ambient gases, the flow rate of oxygen and hydrogen in argon has been changed from 0.1 sccm to 0.5 sccm, respectively. All the IZO thin film has an (222) preferential orientation regardless of ambient gases. The electrical resistivity of the IZO film increased with increasing O2 flow rate, whereas the electrical resistivity decreased sharply under an Ar + H2 atmosphere and was nearly similar regardless of the H2 flow rate. The change of electrical resistivity with changes in the ambient gas composition was mainly interpreted in terms of the charge carrier concentration rather than the charge carrier mobility. All the films showed the average transmittance over 85% in the visible range. The OLED device was fabricated with different IZO substrates made with the configuration of IZO/α-NPD/DPVB/Alq3/LiF/Al in order to elucidate the performance of the IZO substrate. The current density and the luminance of OLED devices with IZO thin films deposited in 0.5 sccm H2 ambient gas are the highest amongst all other films.

Utilization of Piper betle L. Extract for Inactivating Foodborne Bacterial Biofilms on Pitted and Smooth Stainless Steel Surfaces

  • Songsirin Ruengvisesh;Pattarapong Wenbap;Peetitas Damrongsaktrakul;Suchanya Santiakachai;Warisara Kasemsukwimol;Sirilak Chitvittaya;Yossakorn Painsawat;Isaratat Phung-on;Pravate Tuitemwong
    • Journal of Microbiology and Biotechnology
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    • v.33 no.6
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    • pp.771-779
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    • 2023
  • Biofilms are a significant concern in the food industry. The utilization of plant-derived compounds to inactivate biofilms on food contact surfaces has not been widely reported. Also, the increasing negative perception of consumers against synthetic sanitizers has encouraged the hunt for natural compounds as alternatives. Therefore, in this study we evaluated the antimicrobial activities of ethanol extracts, acetone extracts, and essential oils (EOs) of seven culinary herbs against Salmonella enterica serotype Typhimurium and Listeria innocua using the broth microdilution assay. Among all tested extracts and EOs, the ethanol extract of Piper betle L. exhibited the most efficient antimicrobial activities. To evaluate the biofilm inactivation effect, S. Typhimurium and L. innocua biofilms on pitted and smooth stainless steel (SS) coupons were exposed to P. betle ethanol extract (12.5 mg/ml), sodium hypochlorite (NaClO; 200 ppm), hydrogen peroxide (HP; 1100 ppm), and benzalkonium chloride (BKC; 400 ppm) for 15 min. Results showed that, for the untreated controls, higher sessile cell counts were observed on pitted SS versus smooth SS coupons. Overall, biofilm inactivation efficacies of the tested sanitizers followed the trend of P. betle extract ≥ BKC > NaClO > HP. The surface condition of SS did not affect the biofilm inactivation effect of each tested sanitizer. The contact angle results revealed P. betle ethanol extract could increase the surface wettability of SS coupons. This research suggests P. betle extract might be utilized as an alternative sanitizer in food processing facilities.

Surface Engineering of GaN Photoelectrode by NH3 Treatment for Solar Water Oxidation

  • Soon Hyung Kang;Jun-Seok Ha
    • Journal of Electrochemical Science and Technology
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    • v.14 no.4
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    • pp.388-396
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    • 2023
  • Photoelectrochemical (PEC) water splitting is a vital source of clean and sustainable hydrogen energy. Moreover, the large-scale H2 production is currently necessary, while long-term stability and high PEC activity still remain important issues. In this study, a GaN-based photoelectrode was modified by an additional NH3 treatment (900℃ for 10 min) and its PEC behavior was monitored. The bare GaN exhibited a highly crystalline wurtzite structure with the (002) plane and the optical bandgap was approximately 3.2 eV. In comparison, the NH3-treated GaN film exhibited slightly reduced crystallinity and a small improvement in light absorption, resulting from the lattice stress or cracks induced by the excessive N supply. The minor surface nanotexturing created more surface area, providing electroactive reacting sites. From the surface XPS analysis, the formation of an N-Ga-O phase on the surface region of the GaN film was confirmed, which suppressed the charge recombination process and the positive shift of EFB. Therefore, these effects boosted the PEC activity of the NH3-treated GaN film, with J values of approximately 0.35 and 0.78 mA·cm-2 at 0.0 and 1.23 VRHE, respectively, and an onset potential (Von) of -0.24 VRHE. In addition, there was an approximate 50% improvement in the J value within the highly applied potential region with a positive shift of Von. This result could be explained by the increased nanotexturing on the surface structure, the newly formed defect/trap states correlated to the positive Von shift, and the formation of a GaOxN1-x phase, which partially blocked the charge recombination reaction.

Enhancement of oxygen evolution reaction of NiCo LDH nanocrystals using Mo doping (Mo 도핑을 이용한 NiCo LDH 나노결정의 산소발생반응 향상)

  • Kyoungwon Cho;Jeong Ho Ryu
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.34 no.3
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    • pp.92-97
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    • 2024
  • To improve the efficiency of water splitting systems for hydrogen production, the high overvoltages of electrochemical reactions caused by catalysts in the oxygen evolution reaction (OER, Oxygen Evolution Reaction) must be reduced. Among them, LDH (Layered Double Hydroxide) compounds containing transition metal such as Ni, are attracting attention as catalyst materials that can replace precious metals such as platinum that are currently used. In this study, nickel foam, an inexpensive metallic porous material, was used as a support, and NiCo LDH (Layered Double Hydroxide) nanocrystals were synthesized through a hydrothermal synthesis process. In addition, changes in the shape, crystal structure, and water decomposition characteristics of the Mo-doped NiCo LDH nanocrystal samples synthesized by doping Mo to improve OER properties were observed.