468 research outputs found

    Topoisomer Differentiation of Molecular Knots by FTICR MS: Lessons from Class II Lasso Peptides

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    Lasso peptides constitute a class of bioactive peptides sharing a knotted structure where the C-terminal tail of the peptide is threaded through and trapped within an N-terminalmacrolactamring. The structural characterization of lasso structures and differentiation from their unthreaded topoisomers is not trivial and generally requires the use of complementary biochemical and spectroscopic methods. Here we investigated two antimicrobial peptides belonging to the class II lasso peptide family and their corresponding unthreaded topoisomers: microcin J25 (MccJ25), which is known to yield two-peptide product ions specific of the lasso structure under collisioninduced dissociation (CID), and capistruin, for which CID does not permit to unambiguously assign the lasso structure. The two pairs of topoisomers were analyzed by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR MS) upon CID, infrared multiple photon dissociation (IRMPD), and electron capture dissociation (ECD). CID and ECDspectra clearly permitted to differentiate MccJ25 from its non-lasso topoisomer MccJ25-Icm, while for capistruin, only ECD was informative and showed different extent of hydrogen migration (formation of c\bullet/z from c/z\bullet) for the threaded and unthreaded topoisomers. The ECD spectra of the triply-charged MccJ25 and MccJ25-lcm showed a series of radical b-type product ions {\eth}b0In{\TH}. We proposed that these ions are specific of cyclic-branched peptides and result from a dual c/z\bullet and y/b dissociation, in the ring and in the tail, respectively. This work shows the potentiality of ECD for structural characterization of peptide topoisomers, as well as the effect of conformation on hydrogen migration subsequent to electron capture

    ИсслСдованиС углСволокнистых каталитичСских систСм Π½ΠΈΠ·ΠΊΠΎΡ‚Π΅ΠΌΠΏΠ΅Ρ€Π°Ρ‚ΡƒΡ€Π½ΠΎΠ³ΠΎ окислСния БО Π² условиях ΠΈΠΌΠΈΡ‚Π°Ρ†ΠΈΠΈ дыхания

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    A plant for studying fibrous carbon catalytic systems in the low temperature carbon monoxide oxidation reaction under human breath simulation conditions has been developed. Under human breath simulation conditions in absence of water, catalytic activity of the system is attributed to presence of highly dispersed palladium oxide in the palladium-copper-iron catalyst, and the reaction mechanism for these conditions is a separate one.Π Π°Π·Ρ€Π°Π±ΠΎΡ‚Π°Π½Π° установка для испытания углСволокнистых каталитичСских систСм Π½ΠΈΠ·ΠΊΠΎΡ‚Π΅ΠΌΠΏΠ΅Ρ€Π°Ρ‚ΡƒΡ€Π½ΠΎΠ³ΠΎ окислСния БО Π² условиях, ΠΈΠΌΠΈΡ‚ΠΈΡ€ΡƒΡŽΡ‰ΠΈΡ… Π΄Ρ‹Ρ…Π°Π½ΠΈΠ΅ Ρ‡Π΅Π»ΠΎΠ²Π΅ΠΊΠ°. Показано, Ρ‡Ρ‚ΠΎ Π² условиях ΠΈΠΌΠΈΡ‚Π°Ρ†ΠΈΠΈ дыхания ΠΏΡ€ΠΈ отсутствии Π²ΠΎΠ΄Ρ‹ Π² систСмС Π°ΠΊΡ‚ΠΈΠ²Π½ΠΎΡΡ‚ΡŒ Π² Π½ΠΈΠ·ΠΊΠΎΡ‚Π΅ΠΌΠΏΠ΅Ρ€Π°Ρ‚ΡƒΡ€Π½ΠΎΠΌ окислСнии CO обусловлСна Π½Π°Π»ΠΈΡ‡ΠΈΠ΅ΠΌ Π² ΠΏΠ°Π»Π»Π°Π΄ΠΈΠΉΠΌΠ΅Π΄ΡŒΠΆΠ΅Π»Π΅Π·ΠΎΡΠΎΠ΄Π΅Ρ€ΠΆΠ°Ρ‰Π΅ΠΌ ΠΊΠ°Ρ‚Π°Π»ΠΈΠ·Π°Ρ‚ΠΎΡ€Π΅ высокодиспСрсного оксида палладия PdO ΠΈ ΠΏΡ€ΠΎΡ‚Π΅ΠΊΠ°Π½ΠΈΠ΅ΠΌ Ρ€Π΅Π°ΠΊΡ†ΠΈΠΈ ΠΏΠΎ Ρ€Π°Π·Π΄Π΅Π»ΡŒΠ½ΠΎΠΌΡƒ ΠΌΠ΅Ρ…Π°Π½ΠΈΠ·ΠΌΡƒ

    Observation of narrow baryon resonance decaying into pKs0pK^0_s in pA-interactions at 70GeV/c70 GeV/c with SVD-2 setup

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    SVD-2 experiment data have been analyzed to search for an exotic baryon state, the Θ+\Theta^+-baryon, in a pKs0pK^0_s decay mode at 70GeV/c70 GeV/c on IHEP accelerator. The reaction pAβ†’pKs0+XpA \to pK^0_s+X with a limited multiplicity was used in the analysis. The pKs0pK^0_s invariant mass spectrum shows a resonant structure with M=1526Β±3(stat.)Β±3(syst.)MeV/c2M=1526\pm3(stat.)\pm 3(syst.) MeV/c^2 and Ξ“<24MeV/c2\Gamma < 24 MeV/c^2. The statistical significance of this peak was estimated to be of 5.6Οƒ5.6 \sigma. The mass and width of the resonance is compatible with the recently reported Θ+\Theta^+- baryon with positive strangeness which was predicted as an exotic pentaquark (uuddsΛ‰uudd\bar{s}) baryon state. The total cross section for Θ+\Theta^+ production in pN-interactions for XFβ‰₯0X_F\ge 0 was estimated to be (30Γ·120)ΞΌb(30\div120) \mu b and no essential deviation from A-dependence for inelastic events (∼A0.7)(\sim A^{0.7}) was found.Comment: 8 pages, 7 figures, To be submitted to Yadernaya Fizika. v3-v5 - Some references added, minor typos correcte
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