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Park, Sangkyu,Kim, Da-Hye,Lee, Jong-Yeol,Ha, Sun-Hwa,Lim, Sun-Hyung American Chemical Society 2017 Journal of agricultural and food chemistry Vol.65 No.26
<P>We isolated cDNAs encoding flavonol synthase (FLS) from the red onion 'H6' (AcFLS-H6) and the yellow onion 'Hwangryongball' (AcFLS-HRB). We found three amino acid variations between the two sequences. Kinetic analysis with recombinant proteins revealed that AcFLS-HRB exhibited approximately 2-fold higher catalytic efficiencies than AcFLS-H6 for dihydroflavonol substrates and that both proteins preferred dihydroquercetin to dihydrokaempferol. The expression patterns of flavonoid biosynthesis genes corresponded to the accumulation patterns of flavonoid aglycones in both onions. Whereas the other flavonoid biosynthesis genes were weakly expressed in the HRB sheath compared to that of H6, the expression of FLS was similar in both onions. This relatively enhanced FLS expression, along with the higher activity of AcFLS-HRB, could increase the quercetin production in the HRB sheath. The quercetin content was approximately 12-fold higher than the cyanidin content in the H6 sheath, suggesting that FLS has priority in the competition between FLS and dihydroflavonol 4-reductase (DFR) for their substrate dihydroquercetin.</P>
Prediction of Daphnia Production along a Trophic Gradient
Park, Sangkyu*,C.R. Goldman 한국생태학회 2008 Journal of Ecology and Environment Vol.31 No.2
To predict Daphnia secondary productivity along a trophic gradient indexed as total phosphorus(TP) concentration, we estimated energy transfer efficiencies from food quality for Daphnia such as eicosa-Daphnia magna growth experiments were conducted with seston from 9 lakes, ponds and river waters. Primary productivities were estimated from food supply rates in the flow-through experiments, producing energy transfer efficiencies from seston to D. magna. We found DHA content was the best predictor of energy transfer efficiencies among the essential fatty acids. An asymptotic saturation model explained 79.6% of the variability in energy transfer effi-ciencies. Based on empirical data in this study and empirical models from literature, we predict that Daphnia productivity would peak in mesotrophic systems by decreasing food quality and increasing food quantity along trophic gradient.
Rice P450 reductases differentially affect P450-mediated metabolism in bacterial expression systems.
Park, Sangkyu,Kim, Young-Soon,Rupasinghe, Sanjeewa G,Schuler, Mary A,Back, Kyoungwhan Springer-Verlag 2013 Bioprocess and biosystems engineering Vol.36 No.3
<P>We describe cloning and characterization of three rice (Oryza sativa) NADPH-cytochrome P450 reductases (OsCPRs; E.C.1.6.2.4) that are potential donors to plant P450s, including tryptamine 5-hydroxylase (T5H) in serotonin synthesis and cinnamate 4-hydroxylase (C4H) in phenylpropanoid synthesis. All three OsCPR transcripts are induced to varying degrees by stresses. Co-expression of full-length OsCPR1, OsCPR2 and OsCPR3 with either T5H or C4H in E. coli indicated that the OsCPR2/T5H and OsCPR2/C4H constructs displayed the highest T5H and C4H catalytic activities. The N-terminal residues of OsCPR2 were required for peak electron transfer activity to P450 even though deletion mutants with short N-terminal deletions were capable of reducing cytochrome c.</P>
Park, Young-Seuk,Kwon, Yong-Su,Hwang, Soon-Jin,Park, Sangkyu Elsevier 2014 Environmental modelling & software Vol.55 No.-
<P><B>Abstract</B></P> <P>Understanding the pattern of reservoir water quality in relation to morphometry and other landscape characteristics can provide insight into water quality management. We investigated the water quality of 302 reservoirs distributed nationwide in Korea by classifying them using a self-organizing map (SOM), examining how hydrogeomorphometry variables are related to reservoir water quality, and evaluating the effects of variables at different categories including geology, land cover, hydromorphology, and physicochemistry on reservoir water quality through a theoretical path model. The SOM classified the reservoirs into six clusters, from least to most polluted, with differences in physicochemical and hydrogeomorphometry variables between clusters. Water quality exhibits strong relationships with the proportions of urban, agricultural, and forest land cover types in the watersheds. Finally, our results revealed that hydrogeomorphometry of reservoirs and percentages of land cover types within watersheds have a considerable impact on the water quality of adjacent aquatic ecosystems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Water quality of agricultural reservoirs was characterized with variables in multiple spatial scales. </LI> <LI> SOM classified 302 agricultural reservoirs into six different clusters based on water quality. </LI> <LI> The water quality also has strong relations with the proportions of land cover types in watersheds. </LI> <LI> The hydrogeomorphometry of reservoirs have a considerable impact on the water quality of adjacent aquatic ecosystems. </LI> </UL> </P>
Sangkyu Park,Chan-Byoung Chae,Saewoong Bahk IEEE 2015 IEEE wireless communications Vol.22 No.3
<P>To satisfy the ever increasing capacity demand and quality of service requirements of users, 5G cellular systems will take the form of HetNets that consist of macrocells and small cells. To build and operate such systems, mobile operators have given significant attention to cloud radio access networks, C-RANs, due to their beneficial features of performance optimization and cost effectiveness. Along with the architectural enhancement of C-RAN, largescale antennas (a.k.a. massive MIMO) at cell sites contribute greatly to increased network capacity either with higher spectral efficiency or through permitting many users at once. In this article, we discuss the challenging issues of CRAN- based HetNets (H-CRAN), especially with respect to large-scale antenna operation. We provide an overview of existing C-RAN architectures in terms of large-scale antenna operation and promote a partially centralized approach. This approach remarkably reduces fronthaul overheads in C-RANs with large-scale antennas. We also provide some insights into its potential and applicability in the fronthaul bandwidth-limited H-CRAN with large-scale antennas.</P>
First Report of Simplicillium cylindrosporum Isolated from Soil in Korea
( Sangkyu Park ),( Seung-yeol Lee ),( Jae-jin Lee ),( Hyang Burm Lee ),( Leonid Ten ),( Hee-young Jung ) 한국균학회 2017 韓國菌學會誌 Vol.45 No.2
The fungal strain KNU16-006 was isolated from field soil in Daegu, Korea. The isolate was identified as Simplicillium cylindrosporum on the basis of its morphological characterization and phylogenetic analysis using internal transcribed spacer regions of rDNA. This species has not been previously reported in Korea.