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Kinetics of U(VI) reduction control kinetics of U(IV) reoxidation
For the in situ reductive immobilization of U to be an acceptable strategy for the removal of that element from groundwater, the long-term stability of U(IV) must be determined. Rates of biotransformation of Fe species influence the mineralogy of the resulting products (Fredrickson et al., 2003; Senko et al., 2005), and we hypothesize that the rate of U(VI) reduction influences the mineralogy of resultant U(IV) precipitates. We hypothesize that slower rates of U(VI) reduction will yield U(IV) phases that are more resistant to reoxidation, and will therefore be more stable upon cessation of electron donor addition. U(IV) phases formed by relatively slow reduction may be more crystalline or larger in comparison to their relatively rapidly-formed counterparts (Figure 1), thus limiting the reactivity of slowly-formed U(IV) phases toward various oxidants. The physical location of U(IV) precipitates relative to bacterial cells may also limit the reactivity of biogenic U(IV) phases. In this situation, we expect that precipitation of U(IV) within the bacterial cell may protect U(IV) from reoxidation by limiting physical contact between U(IV) and oxidants (Figure 1). We assessed the effect of U(VI) reduction rate on the subsequent reoxidation of biogenic U(IV) and are currently conducting column scale studies to determine whether U(VI) reduction rate can be manipulated by varying the electron donor concentration used to stimulate U(VI) reduction
Topoisomer Differentiation of Molecular Knots by FTICR MS: Lessons from Class II Lasso Peptides
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
ΠΡΡΠ»Π΅Π΄ΠΎΠ²Π°Π½ΠΈΠ΅ ΡΠ³Π»Π΅Π²ΠΎΠ»ΠΎΠΊΠ½ΠΈΡΡΡΡ ΠΊΠ°ΡΠ°Π»ΠΈΡΠΈΡΠ΅ΡΠΊΠΈΡ ΡΠΈΡΡΠ΅ΠΌ Π½ΠΈΠ·ΠΊΠΎΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ½ΠΎΠ³ΠΎ ΠΎΠΊΠΈΡΠ»Π΅Π½ΠΈΡ Π‘Π Π² ΡΡΠ»ΠΎΠ²ΠΈΡΡ ΠΈΠΌΠΈΡΠ°ΡΠΈΠΈ Π΄ΡΡ Π°Π½ΠΈΡ
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·ΡΠ°Π±ΠΎΡΠ°Π½Π° ΡΡΡΠ°Π½ΠΎΠ²ΠΊΠ° Π΄Π»Ρ ΠΈΡΠΏΡΡΠ°Π½ΠΈΡ ΡΠ³Π»Π΅Π²ΠΎΠ»ΠΎΠΊΠ½ΠΈΡΡΡΡ
ΠΊΠ°ΡΠ°Π»ΠΈΡΠΈΡΠ΅ΡΠΊΠΈΡ
ΡΠΈΡΡΠ΅ΠΌ Π½ΠΈΠ·ΠΊΠΎΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ½ΠΎΠ³ΠΎ ΠΎΠΊΠΈΡΠ»Π΅Π½ΠΈΡ Π‘Π Π² ΡΡΠ»ΠΎΠ²ΠΈΡΡ
, ΠΈΠΌΠΈΡΠΈΡΡΡΡΠΈΡ
Π΄ΡΡ
Π°Π½ΠΈΠ΅ ΡΠ΅Π»ΠΎΠ²Π΅ΠΊΠ°. ΠΠΎΠΊΠ°Π·Π°Π½ΠΎ, ΡΡΠΎ Π² ΡΡΠ»ΠΎΠ²ΠΈΡΡ
ΠΈΠΌΠΈΡΠ°ΡΠΈΠΈ Π΄ΡΡ
Π°Π½ΠΈΡ ΠΏΡΠΈ ΠΎΡΡΡΡΡΡΠ²ΠΈΠΈ Π²ΠΎΠ΄Ρ Π² ΡΠΈΡΡΠ΅ΠΌΠ΅ Π°ΠΊΡΠΈΠ²Π½ΠΎΡΡΡ Π² Π½ΠΈΠ·ΠΊΠΎΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ½ΠΎΠΌ ΠΎΠΊΠΈΡΠ»Π΅Π½ΠΈΠΈ CO ΠΎΠ±ΡΡΠ»ΠΎΠ²Π»Π΅Π½Π° Π½Π°Π»ΠΈΡΠΈΠ΅ΠΌ Π² ΠΏΠ°Π»Π»Π°Π΄ΠΈΠΉΠΌΠ΅Π΄ΡΠΆΠ΅Π»Π΅Π·ΠΎΡΠΎΠ΄Π΅ΡΠΆΠ°ΡΠ΅ΠΌ ΠΊΠ°ΡΠ°Π»ΠΈΠ·Π°ΡΠΎΡΠ΅ Π²ΡΡΠΎΠΊΠΎΠ΄ΠΈΡΠΏΠ΅ΡΡΠ½ΠΎΠ³ΠΎ ΠΎΠΊΡΠΈΠ΄Π° ΠΏΠ°Π»Π»Π°Π΄ΠΈΡ PdO ΠΈ ΠΏΡΠΎΡΠ΅ΠΊΠ°Π½ΠΈΠ΅ΠΌ ΡΠ΅Π°ΠΊΡΠΈΠΈ ΠΏΠΎ ΡΠ°Π·Π΄Π΅Π»ΡΠ½ΠΎΠΌΡ ΠΌΠ΅Ρ
Π°Π½ΠΈΠ·ΠΌΡ
Observation of narrow baryon resonance decaying into in pA-interactions at with SVD-2 setup
SVD-2 experiment data have been analyzed to search for an exotic baryon
state, the -baryon, in a decay mode at on IHEP
accelerator. The reaction with a limited multiplicity was
used in the analysis. The invariant mass spectrum shows a resonant
structure with and . The statistical significance of this peak was estimated to be of . The mass and width of the resonance is compatible with the recently
reported - baryon with positive strangeness which was predicted as an
exotic pentaquark () baryon state. The total cross section for
production in pN-interactions for was estimated to be
and no essential deviation from A-dependence for inelastic
events 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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