- Ohmyungsamycins A and B: Cytotoxic and antimicrobial cyclic peptides produced by Streptomyces sp. from a volcanic island
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Ohmyungsamycins A and B (1 and 2), which are new cyclic peptides, were isolated from a marine bacterial strain belonging to the Streptomyces genus collected from a sand beach on Jeju, a volcanic island in the Republic of Korea. Based on the interpretation of the NMR, UV, and IR spectroscopic and MS data, the planar structures of 1 and 2 were elucidated as cyclic depsipeptides bearing unusual amino acid units, including N-methyl-4-methoxytrytophan, β-hydroxyphenylalanine, and N,N-dimethylvaline. The absolute configurations of the α-carbons of the amino acid residues were determined using the advanced Marfey's method. The configurations of the additional stereogenic centers at the β-carbons of the threonine, N-methylthreonine, and β-hydroxyphenylalanine units were assigned by GITC (2,3,4,6-tetra-O-acetyl- β-d-glucopyranosyl isothiocyanate) derivatization and the modified Mosher's method. We have developed a new method utilizing PGME (phenylglycine methyl ester) derivatization coupled with chromatographic analysis to determine the absolute configuration of N,N-dimethylvaline. Our first successful establishment of the absolute configuration of N,N-dimethylvaline using PGME will provide a general and convenient analytical method for determining the absolute configurations of amino acids with fully substituted amine groups. Ohmyungsamycins A and B showed significant inhibitory activities against diverse cancer cells as well as antibacterial effects.
- Um, Soohyun,Choi, Tae Joon,Kim, Heegyu,Kim, Byung Yong,Kim, Seong-Hwan,Lee, Sang Kook,Oh, Ki-Bong,Shin, Jongheon,Oh, Dong-Chan
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p. 12321 - 12329
(2014/01/17)
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- Novel Isobaric Tandem Mass Tags for Quantitative Proteomics and Peptidomics
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Compositions and methods of tagging peptides and other molecules using novel isobaric tandem mass tagging reagents, including novel N,N-dimethylated amino acid 8-plex and 16-plex isobaric tandem mass tagging reagents. The tagging reagents comprise: a) a reporter group having at least one atom that is optionally isotopically labeled; b) a balancing group, also having at least one atom that is optionally isotopically labeled, and c) an amine reactive group. The tagging reagents disclosed herein serve as attractive alternatives for isobaric tag for relative and absolute quantitation (iTRAQ) and tandem mass tags (TMTs) due to their synthetic simplicity, labeling efficiency and improved fragmentation efficiency.
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- Studies on the Stereochemical Characterization of N-Methylated Amino Acids
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Various methods that could be to determine the absolute configuration of N,N-dimethylated amino acids were investigated.Two methods utilizing 1H nuclear magnetic resonance (n.m.r.) spectroscopy were successful.The first involved the conversion of the N,N-
- Ang, Siau-Gek,Low, Siew Hsien
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p. 1591 - 1601
(2007/10/02)
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