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Solar-driven biocatalytic C-hydroxylation through direct transfer of photoinduced electrons
Le, Thien-Kim,Park, Jong Hyun,Choi, Da Som,Lee, Ga-Young,Choi, Woo Sung,Jeong, Ki Jun,Park, Chan Beum,Yun, Chul-Ho The Royal Society of Chemistry 2019 GREEN CHEMISTRY Vol.21 No.3
<P>Despite the immense potential of P450s, the dependence on the nicotinamide cofactor (NADPH) and NADPH-P450 reductase (CPR) limits their employment in the chemical industry. Here, we present a visible light-driven platform for biocatalytic C-hydroxylation reactions using natural flavin molecules, especially flavin mononucleotide, as a photosensitizer. By employing visible light as a source of energy instead of the nicotinamide cofactor, the bacterial CYP102A1 heme domain was successfully applied for photobiocatalytic C-hydroxylation of 4-nitrophenol and lauric acid - in the absence of NADPH and CPR. We present a proof of concept that the photoactivation of flavins is productively coupled with the direct transfer of photoinduced electrons to the P450 heme iron, achieving photobiocatalytic C-hydroxylation reactions.</P>
Kim, Won Jae,Le, Van Phuc,Lee, Hyun Jong,Phan, Huy Thien Elsevier BV 2017 Construction and Building Materials Vol.149 No.-
<P><B>Abstract</B></P> <P>In this study, a rutting model in power law form was proposed considering the shear stress to strength ratio which can be calculated in terms of cohesion (c) and internal friction angle (ϕ) for different asphalt mixtures. Predictive equations for c and ϕ were first developed from laboratory testing at a reference temperature of 50°C using multiple regression analyses considering asphalt binder, aggregate and volumetric properties of different asphalt mixes. The predictive c and ϕ equations were found to have correlation coefficients of 0.87 and 0.86 respectively. The rutting model considers the number of load cycles (N), shear strength ratio, temperature and load duration as main parameters of the permanent strain wherein the coefficients were determined using tri-axial compressive strength and repeated load permanent deformation testing. It was calibrated using field rutting data from twenty-six Westrack pavement sections. Moreover, the rutting model was validated using field performance data obtained from Korean national highways’ long term pavement performance database. It was found from the validation that the model can accurately estimate rut depths under varying load and environmental conditions in the fields.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A rutting model in power law form was proposed. </LI> <LI> The model considers shear stress to strength ratio. </LI> <LI> Predictive equations for cohesion (c) and internal friction angle (ϕ) were developed. </LI> <LI> A rutting model was calibrated and validated using field rutting data. </LI> <LI> The model accurately estimate rut depths under varying load and environmental conditions. </LI> </UL> </P>
CO and CO2 methanation over Ni catalysts supported on alumina with different crystalline phases
Le, Thien An,Kim, Tae Wook,Lee, Sae Ha,Park, Eun Duck Springer-Verlag 2017 Korean Journal of Chemical Engineering Vol.34 No.12
<P>The effect of alumina crystalline phases on CO and CO2 methanation was investigated using alumina-supported Ni catalysts. Various crystalline phases, such as alpha-Al2O3, theta-Al2O3, delta-Al2O3, eta-Al2O3, gamma-Al2O3, and kappa-Al2O3, were utilized to prepare alumina-supported Ni catalysts via wet impregnation. N-2 physisorption, H-2 chemisorption, temperature-programmed reduction with H-2, CO2 chemisorption, temperature-programmed desorption of CO2, and X-ray diffraction were employed to characterize the catalysts. The Ni/theta-Al2O3 catalyst showed the highest activity during both CO and CO2 methanation at low temperatures. CO methanation catalytic activity appeared to be related to the number of Ni surface-active sites, as determined by H-2-chemisorption. During CO2 methanation, Ni dispersion and the CO2 adsorption site were found to influence catalytic activity. Selective CO methanation in the presence of excess CO2 was performed over Ni/gamma-Al2O3 and Ni/delta-Al2O3; these substrates proved more active for CO methanation than for CO2 methanation.</P>