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α-Diazo oxime ethers for N-heterocycle synthesis
Choi, Subin,Ha, Sujin,Park, Cheol-Min The Royal Society of Chemistry 2017 Chemical communications Vol.53 No.45
<P>This Feature Article introduces the preparation and synthetic utility of alpha-diazo oxime ethers. alpha-Oximino carbenes are useful synthons for N-heterocycles, and can be easily prepared from alpha-diazo oxime ethers as precursors. We begin with the preparation of alpha-diazo oxime ethers and their application in [3+ 2] cycloaddition. It turns out that the nature of metals bound to carbenes plays a crucial role in modulating the reactivity of alpha-oximino carbenes, in which copper carbenes smoothly react with enamines, whereas the less reactive enol ethers and nitriles require gold carbenes. In Section 3.2, a discussion on N-O and C-H bond activation is presented. Carbenes derived from diazo oxime ethers show unique reactivity towards N-O and C-H bond activation, in which the proximity of the two functionalities, carbene and oxime ether, dictates the preferred reaction pathways toward pyridines, pyrroles, and 2H-azirines. In Section 3.3, the development of tandem reactions based on alpha-diazo oxime ethers is discussed. The nature of carbenes in which whether free carbenes or metal complexes are involved dissects the pathway and forms different types of 2H-azirines. The 2H-azirine formation turned out to be an excellent platform for the tandem synthesis of N-heterocycles including pyrroles and pyridines. In the last section, we describe the electrophilic activation of 2H-azirines with vinyl carbenes and oximino carbenes. The resulting azirinium species undergo rapid ring expansion rearrangements to form pyridines and pyrazines.</P>
Choi Ji Young,Yun Jihye,Heo Subin,Kim Dong Wook,Choi Sang Hyun,Yoon Jiyoung,Kim Kyuwon,Jung Kee Wook,Myung Seung-Jae 대한영상의학회 2023 Korean Journal of Radiology Vol.24 No.11
Objective: Cine magnetic resonance imaging (MRI) has emerged as a noninvasive method to quantitatively assess bowel motility. However, its accuracy in measuring various degrees of small bowel motility has not been extensively evaluated. We aimed to draw a quantitative small bowel motility score from cine MRI and evaluate its performance in a population with varying degrees of small bowel motility. Materials and Methods: A total of 174 participants (28.5 ± 7.6 years; 135 males) underwent a 22-second-long cine MRI sequence (2-dimensional balanced turbo-field echo; 0.5 seconds per image) approximately 5 minutes after being intravenously administered 10 mg of scopolamine-N-butyl bromide to deliberately create diverse degrees of small bowel motility. In a manually segmented area of the small bowel, motility was automatically quantified using a nonrigid registration and calculated as a quantitative motility score. The mean value (MV) of motility grades visually assessed by two radiologists was used as a reference standard. The quantitative motility score’s correlation (Spearman’s ρ) with the reference standard and performance (area under the receiver operating characteristics curve [AUROC], sensitivity, and specificity) for diagnosing adynamic small bowel (MV of 1) were evaluated. Results: For the MV of the quantitative motility scores at grades 1, 1.5, 2, 2.5, and 3, the mean ± standard deviation values were 0.019 ± 0.003, 0.027 ± 0.010, 0.033 ± 0.008, 0.032 ± 0.009, and 0.043 ± 0.013, respectively. There was a significant positive correlation between the quantitative motility score and the MV (ρ = 0.531, P < 0.001). The AUROC value for diagnosing a MV of 1 (i.e., adynamic small bowel) was 0.953 (95% confidence interval, 0.923–0.984). Moreover, the optimal cutoff for the quantitative motility score was 0.024, with a sensitivity of 100% (15/15) and specificity of 89.9% (143/159). Conclusion: The quantitative motility score calculated from a cine MRI enables diagnosis of an adynamic small bowel, and potentially discerns various degrees of bowel motility.
Functional Characterization and Proteomic Analysis of Porcine Deltacoronavirus Accessory Protein NS7
( Subin Choi ),( Changhee Lee ) 한국미생물 · 생명공학회 2019 Journal of microbiology and biotechnology Vol.29 No.11
Porcine deltacoronavirus (PDCoV) is an emerging swine enteric coronavirus that causes diarrhea in neonatal piglets. Like other coronaviruses, PDCoV encodes at least three accessory or species-specific proteins; however, the biological roles of these proteins in PDCoV replication remain undetermined. As a first step toward understanding the biology of the PDCoV accessory proteins, we established a stable porcine cell line constitutively expressing the PDCoV NS7 protein in order to investigate the functional characteristics of NS7 for viral replication. Confocal microscopy and subcellular fractionation revealed that the NS7 protein was extensively distributed in the mitochondria. Proteomic analysis was then conducted to assess the expression dynamics of the host proteins in the PDCoV NS7-expressing cells. Highresolution two-dimensional gel electrophoresis initially identified 48 protein spots which were differentially expressed in the presence of NS7. Seven of these spots, including two upregulated and five down-regulated protein spots, showed statistically significant alterations, and were selected for subsequent protein identification. The affected cellular proteins identified in this study were classified into functional groups involved in various cellular processes such as cytoskeleton networks and cell communication, metabolism, and protein biosynthesis. A substantial down-regulation of α-actinin-4 was confirmed in NS7-expressing and PDCoV-infected cells. These proteomic data will provide insights into the understanding of specific cellular responses to the accessory protein during PDCoV infection.
Status quo of taxonomic studies on Encyrtidae (Hymenoptera: Chalcidoidea) in Korea
Choi Subin,Il-Kwon Kim 한국응용곤충학회 2018 한국응용곤충학회 학술대회논문집 Vol.2018 No.10
Encyrtidae, belonging to Chalcidoidea (Hymenoptera), includes about 4,000 species in 460 genera worldwide. Many of the members are very important biological control agents of insect pests such as scale-insects (Hemiptera, Coccoidea). Many species have been relatively well studied in various taxonomic and biological fields because of economical and ecological importance of Encyrtidae. However, Korean encyrtids are poorly studied so far. In this presentation we will introduce the current status of taxonomy and biological characteristics of Encyrtidae. In addition further study plans are also presented.
Two new records of the genus Aphidius (Braconidae: Aphidiinae) from South Korea
Subin Choi,Deok-Seo Ku,Hyojoong Kim 한국응용곤충학회 2017 한국응용곤충학회 학술대회논문집 Vol.2017 No.04
Aphidiinae in Braconidae includes more than 400 species within approximately 60 genera worldwide. Species of Aphidiinae are mostly known as solitary koinobiont endoparasitoids specifically associated with aphid hosts, and some of them are used for biological control. In the present study, two aphiniine species are newly recognized from South Korea based on morphological and molecular study: Aphidius rhopalosiphi de Stefani-Perez 1902 and A. uzbekistanicus Luzhetzki 1960. Although It was very difficult to discriminate two species morphologically, we cleary identified them by using COI (cytochrome c oxidase subunit I) DNA Barcode sequences. Here we present their morphological descriptions, illustrations and barcoding results.