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Zhu, Qiankun,Zhu, Mengli,Fan, Gaotao,Zou, Jiaxin,Feng, Peichun,Liu, Zubi,Wang, Wanjun Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.1
Coptis chinensis 3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase (HOMT), an essential enzyme in the berberine biosynthetic pathway, catalyzes the methylation of 3'-hydroxy-N-methylcoclaurine (HMC) producing reticuline. A 3D model of HOMT was constructed by homology modeling and further subjected to docking with its ligands and molecular dynamics simulations. The 3D structure of HOMT revealed unique structural features which permitted the methylation of HMC. The methylation of HMC was proposed to proceed by deprotonation of the 4'-hydroxyl group via His257 and Asp258 of HOMT, followed by a nucleophilic attack on the SAM-methyl group resulting in reticuline. HOMT showed high substrate specificity for methylation of HMC. The study evidenced that Gly117, Thr312 and Asp258 in HOMT might be the key residues for orienting substrate for specific catalysis.
Meng Jiang,Xuhai Li,Jiliang Zhu,Xiaohong Zhu,Wei Shi,Lihua Li,Dingquan Xiao,Jianguo Zhu 한국물리학회 2010 Current Applied Physics Vol.10 No.2
Pb0.99Nb0.02(Zr0.95Ti0.05)0.98O3 (PNZT95/5) ceramics with 1 mol% and without Mn doping were prepared via conventional solid state reaction process. X-ray diffraction patterns show that the PNZT95/5 and Mn-doped PNZT95/5 (PNZTM95/5) ceramics, with composition near the boundary of the ferroelectric phase (FE)/antiferroelectric phase (AFE), have a rhombohedral perovskite structure. The ferroelectric behavior of PNZT95/5 ceramics is strongly affected by Mn doping. Without any aging process the PNZTM95/5 ceramics possess double hysteresis loops (P–E loops), whereas the PNZT95/5 ceramics possess normal single hysteresis loops. Due to the defect dipoles formed by effectively negatively charged Mn3+ dopants and positively charged O2- vacancies, the PNZTM95/5 ceramics exhibit the double P–E loops. The defect dipole effect has been proved by investigating the P–E loops under different external fields. As a result, the PNZTM95/5 ceramics become ‘‘hardened”, exhibiting a high mechanical quality factor (1300).
Qiankun Zhu,Mengli Zhu,Gaotao Fan,Jiaxin Zou,Peichun Feng,Zubi Liu,Wanjun Wang 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.1
Coptis chinensis 3'-hydroxy-N-methylcoclaurine 4'-O-methyltransferase (HOMT), an essential enzyme in the berberine biosynthetic pathway, catalyzes the methylation of 3'-hydroxy-N-methylcoclaurine (HMC) producing reticuline. A 3D model of HOMT was constructed by homology modeling and further subjected to docking with its ligands and molecular dynamics simulations. The 3D structure of HOMT revealed unique structural features which permitted the methylation of HMC. The methylation of HMC was proposed to proceed by deprotonation of the 4'-hydroxyl group via His257 and Asp258 of HOMT, followed by a nucleophilic attack on the SAM-methyl group resulting in reticuline. HOMT showed high substrate specificity for methylation of HMC. The study evidenced that Gly117, Thr312 and Asp258 in HOMT might be the key residues for orienting substrate for specific catalysis.
Synthesis and Structural Studies of an Organic Complex and its Association with BSA
Meng, Fa-Yan,Yu, Sheng-Rong,Liang, Li-Xi,Zhong, Xue-Ping,Wang, Li,Zhu, Jin-Mei,Lin, Cui-Wu Korean Chemical Society 2011 Bulletin of the Korean Chemical Society Vol.32 No.7
The self-assembly of one novel organic complex based on chlorogenic acid (HCA) and 2,2'-bipyridine (2,2'-bipy) has been synthesized and characterized. The complex achieved by hydrogen-bonding interactions, adopted a 1:1 stoichiometry in a solid state. The proton transfer occurred from the carboxyl oxygen to the aromatic nitrogen atom to form salts CA${\cdot}$(2,2'-Hbipy), the 2,2'-Hbipy molecule individually occupies the pseudo-tetragonum that is formed with CA. In this paper, the interactions of CA${\cdot}$(2,2'-Hbipy) with bovine serum albumin (BSA) were studied by fluorescence spectrometry. For CA${\cdot}$(2,2'-Hbipy), HCA and 2,2'-bipy, the average quenching constants for BSA were $2.4384{\times}10^4$, $4.653{\times}10^3$, and $3.059{\times}10^3\;L{\cdot}mol^{-1}$, respectively. The mechanism for protein fluorescence quenching is apparently governed by a static quenching process. The Stern-Volmer quenching constants and corresponding thermodynamic parameters ${\Delta}$H, ${\Delta}$G and ${\Delta}$S were calculated. The binding constants and the number of binding sites were also investigated. The conformational changes of BSA were observed from synchronous fluorescence spectra.
Meng, Ze-Da,Cho, Sun-Bok,Ghosh, Trisha,Zhu, Lei,Choi, Jong-Geun,Park, Chong-Yeon,Oh, Won-Chun Materials Research Society of Korea 2012 한국재료학회지 Vol.22 No.2
AC and ZnS modified $TiO_2$ composites (AC/ZnS/$TiO_2$) were prepared using a sol-gel method. The composite obtained was characterized by Brunauer-Emmett-Teller (BET) surface area measurements, X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, scanning electron microscope (SEM) analysis, and according to the UV-vis absorption spectra (UV-vis). XRD patterns of the composites showed that the AC/ZnS/$TiO_2$ composites contain a typical single and clear anatase phase. The surface properties as observed by SEM present the characterization of the texture of the AC/ZnS/$TiO_2$ composites, showing a homogenous composition in the particles showing the micro-surface structures and morphology of the composites. The EDX spectra of the elemental identification showed the presence of C and Ti with Zn and S peaks for the AC/ZnS/$TiO_2$ composite. UV-vis patterns of the composites showed that these composites had greater photocatalytic activity under visible light irradiation. A rhodamine B (Rh.B) solution under visible light irradiation was used to determine the photocatalytic activity. The degradation of Rh.B was determined using UV/Vis spectrophotometry. An increase in the photocatalytic activity was observed. From the photocatalytic results, the excellent activity of the Y-fullerene/$TiO_2$ composites for the degradation of methylene blue under visible irradiation could be attributed to an increase in the photo-absorption effect caused by the ZnS and to the cooperative effect of the AC.
Meng, Ze-Da,Zhu, Lei,Ghosh, Trisha,Park, Chong-Yeon,Ullah, Kefayat,Nikam, Vikram,Oh, Won-Chun Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.11
$Ag_2Se$-Graphene/$TiO_2$ composite was synthesized by a facile sonochemical method. The as-prepared products were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectrophotometer. During the reaction, both of the reduction of graphene oxide and loading of $Ag_2Se$ and $TiO_2$ particles were achieved. The as-prepared $Ag_2Se$-Graphene/$TiO_2$ composites possessed great adsorptivity of dyes, extended light absorption range, and efficient charge separation properties simultaneously. Hence, in the photodegradation of rhodamine B (Rh.B), a significant enhancement in the reaction rate was observed with $Ag_2Se$-Graphene/$TiO_2$ composites, compared to the pure $TiO_2$. The high activity can be attributed to the synergetic effects of high charge mobility, and red shift in absorption edge of $Ag_2Se$-Graphene/$TiO_2$ composites.
Zhu, Lei,Tang, Jia-Yao,Fan, Jia-Yi,Sun, Chen,Meng, Ze-Da,Oh, Won-Chun Materials Research Society of Korea 2021 한국재료학회지 Vol.31 No.11
Herein, a series of g-C<sub>3</sub>N<sub>4</sub> modified Bi<sub>2</sub>MoO<sub>6</sub> nanocomposites using Bi<sub>2</sub>MoO<sub>6</sub> and melamine as original materials are fabricated via sintering process. For presynthesis of Bi<sub>2</sub>MoO<sub>6</sub> an ultrasonic-assisted hydrothermal technique is researched. The structure and composition of the nanocomposites are characterized by Raman spectroscopy, X-ray diffraction (XRD), and high-resolution field emission scanning electron microscopy (SEM). The improved photoelectrochemical properties are studied by photocurrent density, EIS, and amperometric i-t curve analysis. It is found that the structure of Bi<sub>2</sub>MoO<sub>6</sub> nanoparticles remains intact, with good dispersion status. The as-prepared g-C<sub>3</sub>N<sub>4</sub>/Bi<sub>2</sub>MoO<sub>6</sub> nanocomposites (BMC 5-9) are selected and investigated by SEM analysis, which inhibits special morphology consisting of Bi<sub>2</sub>MoO<sub>6</sub> nanoparticles and some g-C<sub>3</sub>N<sub>4</sub> nanosheets. The introduction of small sized g-C<sub>3</sub>N<sub>4</sub> nanosheets in sample BMC 9 is effective to improve the charge separation and transfer efficiency, resulting in enhancing of the photoelectric behavior of Bi<sub>2</sub>MoO<sub>6</sub>. The improved photoelectronic behavior of g-C<sub>3</sub>N<sub>4</sub>/Bi<sub>2</sub>MoO<sub>6</sub> may be attributed to enhanced charge separation efficiency, photocurrent stability, and fast electron transport pathways for some energy applications.
Meng, Ze-Da,Ullah, Kefayat,Zhu, Lei,Ye, Shu,Oh, Won-Chun The Korean Ceramic Society 2014 한국세라믹학회지 Vol.51 No.4
ZnS and $ZnS/TiO_2$ were prepared by chemical deposition. The prepared photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscopy (TEM). The generation of reactive oxygen species was detected by monitoring the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). Excellent catalytic degradation of methylene blue (MB) solution was observed using the $ZnS/TiO_2$ composites during irradiation with visible light. The results show that the photocatalytic performance of $TiO_2$ nanoparticles is improved by loading with ZnS.