Electrospray ionization mass spectrometric analysis of microcystins, cyclic heptapeptide hepatotoxins: modulation of charge states and [M + H]+ to [M + Na]+ ratio

AbstractElectrospray ionization mass spectrometry was used to develop a rapid, sensitive, and accurate method for determination and identification of hepatotoxic microcystins, cyanobacterial cyclic heptapeptides. To optimize the electrospray ionization conditions, factors affecting charge state distribution, such as amino acid components of sample, proton affinity of the additives, and additive concentration, were investigated in detail and a method for controlling charge states was developed to provide molecular-related ions for assignment of molecular weight and reasonably abundant precursor ions for MS/MS analysis. A procedure for identification of microcystins consisting of known amino acids was proposed: for microcystins giving abundant [M + 2H]2+ ions, the addition of nitrogen-containing bases to the aqueous sample solution is effective to obtain an increased intensity of [M + H]+ ions, whereas the addition of Lewis acids containing nitrogen can produce increased abundances of [M + 2H]2+ ions for microcystins giving weak [M + 2H]2+ ions. Microcystins possessing no arginine residue always give sodium adduct ions [M + Na]+ as the base peak, and these are difficult to fragment via low energy collision-induced dissociation to yield structurally informative products; the addition of oxalic acid increases [M + H]+ ion abundances, and these fragment readily

Rigid-Plastic Deformation of Inhomogeneous Material with Elliptic Inclusions Sliding along Boundary

The influence of the slip between the inclusion and the matrix during the plastic deformation of inhomogeneous material with elliptic inclusions is investigated. The material is assumed to be rigid-plastic. The boundary slip region is modeled by assuming lower yield stress for the thin boundary region than those of the inclusion and the matrix. The rigid-plastic finite element method is used for the numerical calculation under the plane strain condition. The effects of the aspect ratio of the inclusion, the yield stress of the boundary region, and the volume fraction of the inclusion on the deformation mode are studied. The patterns of the strain concentration and the averaged flow stress of the inhomogeneous material are also discussed. The results may be helpful for understanding creep or superplastic deformation of metals with inclusions

Effects of Melophlins on Colony Formation of Chinese Hamster V79 Cells and IL-8 Production in PMA-stimulated HL-60 Cells

We have recently isolated four new melophlins P (1), Q (2), R (3), and S (4) together with seven known melophlins A (5), D (6), E (7), G (8), H (9), I (10), and O (11) from two marine sponges of the genus Melophlus collected in Palau. In this study, the influence of these compounds on the colony formation of Chinese hamster V79 cells and the production of IL-8 in PMA-stimulated HL-60 cells were examined. These 11 compounds did not show any effect on IL-8 production. The EC50 values of compounds 2, 3, 4, 5, 7, 9, 10, and 11 against V79 cells were 44.0, 13.3, 16.7, 27.2, 19.8, 8.5, 23.1, and 9.6 μM, respectively. The linear-chain-type compounds (1, 6, and 8) were not active against V79 cells at 50 μM. Although the growth inhibitory activity of these melophlins was not remarkable, some structure-activity relationships of these compounds against V79 and murine leukemia L1210 cells were observed

Two New Tryptamine Derivatives, Leptoclinidamide and (-)-Leptoclinidamine B, from an Indonesian Ascidian Leptoclinides dubius

Two new tryptamine-derived alkaloids, named as leptoclinidamide (1) and (-)-leptoclinidamine B (2), were isolated from an Indonesian ascidian Leptoclinides dubius together with C2-α-D-mannosylpyranosyl-L-tryptophan (3). The structure of 1 was assigned on the basis of spectroscopic data for 1 and its N-acetyl derivative (4). Compound 1 was an amide of tryptamine with two β-alanine units. Although the planar structure of 2 is identical to that of the known compound (+)-leptoclinidamine B (5), compound 2 was determined to be the enantiomer of 5 based on amino acid analysis using HPLC methods. Compounds 1 to 4 were evaluated for cytotoxicity against two human cancer cell lines, HCT-15 (colon) and Jurkat (T-cell lymphoma) cells, but none of the compounds showed activity

イトマキヒトデに逃避行動を起こさせるニチリンヒトデ分離画分中の核酸イノシンとグアノシンの同定

東京水産大学海洋環境学科青森県水産増殖センター青森県水産増殖センター東京水産大学資源育成学科東京水産大学海洋環境学

パラオで採集した海洋糸状菌TUF98F139株が生産する微少管重合阻害活性物質

東京水産大学海洋環境学科東京水産大学海洋環境学科東京水産大学海洋環境学科東京大学分子細胞生物学研究所東京水産大学練習船海鷹丸東京水産大学練習船海鷹

A Marine Sulfate-Reducing Bacterium Producing Multiple Antibiotics: Biological and Chemical Investigation

A marine sulfate-reducing bacterium SRB-22 was isolated by means of the agar shake dilution method and identified as Desulfovibrio desulfuricans by morphological, physiological and biochemical characteristics and 16S rDNA analysis. In the bioassay, its extract showed broad-spectrum antimicrobial activity using the paper disc agar diffusion method. This isolate showed a different antimicrobial profile than either ampicillin or nystatin and was found to produce at least eight antimicrobial components by bioautography. Suitable fermentation conditions for production of the active constituents were determined to be 28 day cultivation at 25 °C to 30 °C with a 10% inoculation ratio. Under these conditions, the SRB-22 was fermented, extracted and chemically investigated. So far an antimicrobial compound, mono-n-butyl phthalate, and an inactive compound, thymine, have been isolated and characterized

Ion release from experimental Au-Pt-based metal-ceramic alloys

Objective. The aim of the study was to assess the effect of individual metallic elements within experimental Au-Pt-based dental alloys for porcelain veneering on ion release. Methods. A binary Au-10 at% Pt alloy (AP10) was designed as a parent alloy. Six ternary AP10-X (X = In/Fe/Sn/Zn) and four quaternary (AP10-In2)-Y (Y = Fe/Sn/Zn) alloys containing oxide-forming elements, X and Y, up to 2 at% were prepared and ion release from the experimental alloys in deionized water and commercial soft drink was examined. For ion release determination samples with size 10 mm x 10 mm x 0.5 mm were immersed in 20 ml of deionized water for 5 min. Samples were then removed and immersed in 20 ml of Sprite Light (R) for a further 5 min, and 2 h at 37 degrees C. The amounts of ions released in the test solutions were analyzed by inductively coupled plasma-mass spectrometry. Results. When looking at individual elemental ion release, the order of the amount of dissolved ions was Fe > Zn > In > Sn. Among the base metal elements examined, Fe showed significantly higher levels of ion release than the other base metal elements for all three testing conditions (P < 0.05). When looking at the effects of test solution on ion release from the alloys, Sprite Light (R) caused significantly higher level of ion release than deionized water, with the exception of In in the ternary AP10-In1.0 and AP10-In1.7 alloys and the quaternary (AP10-In2)-Sn1.0 alloy, which showed similar or slightly greater amounts of ion release into deionized water. Significance. Significant ion release was only observed from the Fe element. Sn and In elements showed less ion release than the Fe and Zn elements. Accordingly, Sn and In elements should be recommended as oxide-forming elements in Au-Pt-based metal-ceramic systems. (C) 2010 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved