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Son, Sangkeun,Ko, Sung-Kyun,Kim, Seung Min,Kim, Eun,Kim, Gil Soo,Lee, Byeongsan,Ryoo, In-Ja,Kim, Won-Gon,Lee, Jung-Sook,Hong, Young-Soo,Jang, Jae-Hyuk,Ahn, Jong Seog American Chemical Society and American Society of 2018 Journal of natural products Vol.81 No.11
<P>Three cyclic lipopeptides, including one known (<B>1</B>) and two new (<B>2</B> and <B>3</B>) compounds, that possess the rare enamide linkage group were discovered from <I>Streptomyces</I> sp. KCB14A132, an actinobacterium isolated from a soil sample collected from Jeung Island, Korea. The NMR and MS-based characterization showed that they differed in the amino acid residues in the peptide backbone. Application of Marfey’s analysis, GITC derivatization, and modified Mosher’s method, as well as ECD measurements provided the absolute configurations of enamidonin (<B>1</B>) and those of new compounds enamidonins B and C (<B>2</B> and <B>3</B>). The two new enamidonin analogues were shown to exhibit antibacterial activity against Gram-positive bacteria including methicillin-resistant and quinolone-resistant <I>Staphylococcus aureus</I>. Furthermore, evaluation of the extraction conditions and a close inspection of the LC-MS chromatograms revealed that the <I>N</I>,<I>N</I>-acetonide unit of the enamidonin family was formed during the acetone extraction process. The chemically prepared deacetonide derivatives of enamidonins were found to lack antibacterial activity, demonstrating that the dimethylimidazolidinone residue is necessary for antibacterial activity.</P> [FIG OMISSION]</BR>
Son, Sangkeun,Jang, Mina,Lee, Byeongsan,Hong, Young-Soo,Ko, Sung-Kyun,Jang, Jae-Hyuk,Ahn, Jong Seog American Chemical Society and American Society of 2018 Journal of natural products Vol.81 No.10
<P>The advances of genomic sequence analyses and genome mining tools have enabled the exploration of untapped microbial natural products. Through genome mining studies to discover cryptic natural products, we found biosynthetic genes encoding a new lasso peptide in the genome sequence of a soil bacterium, <I>Streptomyces</I> sp. KCB13F003 isolated from Ulleung Island (a small volcanic island), Korea. The production and purification of the encoded peptide, named ulleungdin, were achieved by optimizing the culture conditions followed by LC-MS-targeted isolation. Structure elucidation was performed by NMR spectroscopic and MS spectrometric analyses and chemical means (Marfey’s and GITC derivatizations), proving ulleungdin to be a new 15-mer class II lasso peptide with a threaded structure. Biological evaluation with the cell invasion assay and time-lapse cell tracking analysis revealed that ulleungdin has significant inhibitory activities against cancer cell invasion and migration.</P> [FIG OMISSION]</BR>
Son, Sangkeun,Ko, Sung-Kyun,Jang, Mina,Lee, Jae Kyoung,Ryoo, In-Ja,Lee, Jung-Sook,Lee, Kyung Ho,Soung, Nak-Kyun,Oh, Hyuncheol,Hong, Young-Soo,Kim, Bo Yeon,Jang, Jae-Hyuk,Ahn, Jong Seog American Chemical Society 2015 ORGANIC LETTERS Vol.17 No.16
<P>Two novel cyclic depsipeptides, ulleungamides A (1) and B (2), were isolated from cultures of terrestrial Streptomyces sp. Their structures were determined by analyses of spectroscopic data and various chemical transformations, including modified Mosher's method, advanced Marfey's method, PGMF,, GITC derivatizations, and Snatzke's method. Ulleungamides were determined to be a new class of peptides bearing unprecedented units, such as 5-hydroxy-6-methyl-2,3-dehydropipecolic acid, 4,5-dihydroxy-6-methyl-2,3-dehydropipecolic acid, and amino-linked 2-isopropylsuccinic acid. Ulleungamide A displayed growth inhibitory activity against Staphylococcus aureus and Salmonella typhimurium without cytotoxicity.</P>
Son, Sangkeun,Ko, Sung-Kyun,Jang, Mina,Lee, Jae Kyoung,Kwon, Min Cheol,Kang, Dong Hyo,Ryoo, In-Ja,Lee, Jung-Sook,Hong, Young-Soo,Kim, Bo Yeon,Jang, Jae-Hyuk,Ahn, Jong Seog American Chemical Society and American Society of 2017 Journal of natural products Vol.80 No.5
<P>A bioassay-guided investigation in conjunction with chemical screening led to the isolation of three new glycosides, ulleungoside (1), 2-methylaminobenzoyl 6-deoxy-alpha-L-talopyranoside (2), and naphthomycinoside (3), along with three known secondary metabolites (5-7) from Streptomyces sp. KCB13F030. Their structures were elucidated by detailed NMR and MS spectroscopic analyses. Absolute configurational analysis of the sugar units based on the magnitudes of the coupling constants, NOESY correlations, chemical derivatization, and optical rotation measurements revealed that compounds 1-3 and 5 incorporate the rare deoxyhexose 6-deoxy-alpha-L-talopyranose. The absolute configuration of a polyketide extender unit of 3 was determined by applying the J-based configuration analysis and modified Mosher's method. Ulleungoside (1) and naphthomycin A (7) showed activity. Further bioevaluation revealed that compounds 1 and cell lines, and compounds 5 and 6, which are members of the 2 plying the J-based configuration analysis and modified Mosher's in vitro inhibitory effects against indoleamine 2,3-dioxygenase 7 had moderate antiproliferative activities against several cancer piericidin family, induced autophagosome accumulation.</P>
Son, Sangkeun,Hong, Young-Soo,Jang, Mina,Heo, Kyung Taek,Lee, Byeongsan,Jang, Jun-Pil,Kim, Jong-Won,Ryoo, In-Ja,Kim, Won-Gon,Ko, Sung-Kyun,Kim, Bo Yeon,Jang, Jae-Hyuk,Ahn, Jong Seog American Chemical Society and American Society of 2017 Journal of natural products Vol.80 No.11
<P>Analysis of the genome sequence of <I>Streptomyces</I> sp. KCB13F003 showed the presence of a cryptic gene cluster encoding flavin-dependent halogenase and nonribosomal peptide synthetase. Pleiotropic approaches using multiple culture media followed by LC-MS-guided isolation and spectroscopic analysis enabled the identification of two new chlorinated cyclic hexapeptides, ulleungmycins A and B (<B>1</B> and <B>2</B>). Their structures, including absolute configurations, were determined by 1D and 2D NMR techniques, advanced Marfey’s analysis, and GITC derivatization. The new peptides, featuring unusual amino acids 5-chloro-<SMALL>l</SMALL>-tryptophan and <SMALL>d</SMALL>-homoleucine, exhibited moderate antibacterial activities against Gram-positive pathogenic bacteria including methicillin-resistant and quinolone-resistant <I>Staphylococcus aureus</I>.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jnprdf/2017/jnprdf.2017.80.issue-11/acs.jnatprod.7b00660/production/images/medium/np-2017-00660j_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/np7b00660'>ACS Electronic Supporting Info</A></P>
Son, Sangkeun,Hong, Young-Soo,Futamura, Yushi,Jang, Mina,Lee, Jae Kyoung,Heo, Kyung Taek,Ko, Sung-Kyun,Lee, Jung Sook,Takahashi, Shunji,Osada, Hiroyuki,Jang, Jae-Hyuk,Ahn, Jong Seog American Chemical Society 2018 ORGANIC LETTERS Vol.20 No.22
<P>New glycosylated 26-membered triene macrolides catenulisporolides, the first polyketide metabolites from <I>Catenulispora</I> species, were obtained by targeting slow-forming colonies on selection agar plates and applying long-term cultivation. Their structures, including the full stereochemistry, were defined by comprehensive spectroscopic and chemical methods and confirmed by bioinformatics analysis. Analysis of the genome sequence revealed the responsible biosynthetic gene cluster spanning ∼160 kbp, and feeding experiments with isotope-labeled precursors showed that isovaleric acid acts as a rare starter unit. Catenulisporolides exhibited antimalarial activities against resistant strains of <I>Plasmodium falciparum</I>, and enhanced activity was observed in semisynthetic derivatives.</P> [FIG OMISSION]</BR>
고탄소 크롬 베어링강의 구름 피로에 의한 조직 변화 연구
김민환(Minhwan Kim),손찬현(Chanhyun Son),김상근(Sangkeun Kim),송복한(Bokhan Song) 한국트라이볼로지학회 2006 한국트라이볼로지학회 학술대회 Vol.2006 No.11
The microstructural changes of bearing steels caused by the rolling contact fatigue(RCF) under high temperature was investigated. A TRCF test was carried out to reveal the microstructural changes of through hardened bearing steel with different rolling contact fatigue cycles. White etched area(WEA) was shown at maximum herzian contact stress region after RCF test. Chemical composition and phase were changed in WEA. The RCF under high temperature and stress contribute to the early formation of WEA which eventually leads to spalling failure.
Hwang Gwi Ja,Roh Jongtae,Son Sangkeun,Lee Byeongsan,Jang Jun-Pil,Hur Jae-Seoun,Hong Young-Soo,Ahn Jong Seog,Ko Sung-Kyun,Jang Jae-Hyuk 한국미생물·생명공학회 2023 Journal of microbiology and biotechnology Vol.33 No.11
A recently bioinformatic analysis of genomic sequences of fungi indicated that fungi are able to produce more secondary metabolites than expected. Despite their potency, many biosynthetic pathways are silent in the absence of specific culture conditions or chemical cues. To access cryptic metabolism, 108 fungal strains isolated from various sites were cultured with or without Streptomyces sp. 13F051 which mainly produces trichostatin analogues, followed by comparison of metabolic profiles using LC-MS. Among the 108 fungal strains, 14 produced secondary metabolites that were not recognized or were scarcely produced in mono-cultivation. Of these two fungal strains, Myrmecridium schulzeri 15F098 and Scleroconidioma sphagnicola 15S058 produced four new compounds (1-4) along with a known compound (5), demonstrating that all four compounds were produced by physical interaction with Streptomyces sp. 13F051. Bioactivity evaluation indicated that compounds 3-5 impede migration of MDA-MB-231 breast cancer cells.
Production of Bioactive 3’-Hydroxystilbene Compounds Using the Flavin-Dependent Monooxygenase Sam5
( Kyung Taek Heo ),( Byeongsan Lee ),( Sangkeun Son ),( Jong Seog Ahn ),( Jae-hyuk Jang ),( Young-soo Hong ) 한국미생물생명공학회(구 한국산업미생물학회) 2018 Journal of microbiology and biotechnology Vol.28 No.7
The flavin-dependent monooxygenase Sam5 was previously reported to be a bifunctional hydroxylase with coumarate 3-hydroxylase and resveratrol 3’-hydroxylase activities. In this article, we showed the Sam5 enzyme has 3’-hydroxylation activities for methylated resveratrols (pinostilbene and pterostilbene), hydroxylated resveratrol (oxyresveratrol), and glycosylated resveratrol (piceid) as substrates. However, piceid, a glycone-type stilbene used as a substrate for bioconversion experiments with the Sam5 enzyme expressed in Escherichia coli, did not convert to the hydroxylated compound astringin, but it was converted by in vitro enzyme reactions. Finally, we report a novel catalytic activity of Sam5 monooxygenase for the synthesis of piceatannol derivatives, 3’-hydroxylated stilbene compounds. Development of this bioproduction method for the hydroxylation of stilbenes is challenging because of the difficulty in expressing P450-type hydroxylase in E. coli and regiospecific chemical synthesis.
Park, Sang Jun,Shin, Joo Young,Kim, Sangkeun,Son, Jaemin,Jung, Kyu-Hwan,Park, Kyu Hyung KOREAN ACADEMY OF MEDICAL SCIENCE 2018 JOURNAL OF KOREAN MEDICAL SCIENCE Vol.33 No.43
<P><B>Background</B></P><P>We described a novel multi-step retinal fundus image reading system for providing high-quality large data for machine learning algorithms, and assessed the grader variability in the large-scale dataset generated with this system.</P><P><B>Methods</B></P><P>A 5-step retinal fundus image reading tool was developed that rates image quality, presence of abnormality, findings with location information, diagnoses, and clinical significance. Each image was evaluated by 3 different graders. Agreements among graders for each decision were evaluated.</P><P><B>Results</B></P><P>The 234,242 readings of 79,458 images were collected from 55 licensed ophthalmologists during 6 months. The 34,364 images were graded as abnormal by at-least one rater. Of these, all three raters agreed in 46.6% in abnormality, while 69.9% of the images were rated as abnormal by two or more raters. Agreement rate of at-least two raters on a certain finding was 26.7%–65.2%, and complete agreement rate of all-three raters was 5.7%–43.3%. As for diagnoses, agreement of at-least two raters was 35.6%–65.6%, and complete agreement rate was 11.0%–40.0%. Agreement of findings and diagnoses were higher when restricted to images with prior complete agreement on abnormality. Retinal/glaucoma specialists showed higher agreements on findings and diagnoses of their corresponding subspecialties.</P><P><B>Conclusion</B></P><P>This novel reading tool for retinal fundus images generated a large-scale dataset with high level of information, which can be utilized in future development of machine learning-based algorithms for automated identification of abnormal conditions and clinical decision supporting system. These results emphasize the importance of addressing grader variability in algorithm developments.</P>