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141.
The histidine-rich peptide H5WYG (GLFHAIAHFIHGGWHGLIHGWYG) was found to induce membrane fusion at physiologic pH in the presence of zinc chloride. In this study, we examined the ion selectivity of the interaction of Zn(2+) with H5WYG. This investigation was conducted by using adsorption at air/water interface and mass spectrometry. We found that a peptide-metal complex is formed with Zn(2+) ions. Electrospray ionisation-mass spectrometry (ESI-MS) reveals that the [H5WYG + Zn + 2H](4+), [H5WYG + Zn + H](3+) and [H5WYG + Zn](2+) ions, appearing by increasing the amount of Zn(2+) equivalent, correspond to a monomolecular H5WYG - Zn(2+) complex. Tandem mass spectrometry (MS/MS) provides evidence for the binding of the single Zn(2+) ion to the H(11) and H(19) and probably H(15) residues. 相似文献
142.
Nunzio Tuccitto Lara Lobo Agnès Tempez Ivan Delfanti Patrick Chapon Stela Canulescu Nerea Bordel Johann Michler Antonino Licciardello 《Rapid communications in mass spectrometry : RCM》2009,23(5):549-556
We demonstrate the potential of an innovative technique, pulsed radiofrequency glow discharge time‐of‐flight mass spectrometry, for the molecular depth profiling of polymer materials. The technique benefits from the presence, in the afterglow of the pulsed glow discharge, of fragment ions that can be related to the structures of the polymers under study. Thin films of different polymers (PMMA, PET, PAMS, PS) were successfully profiled with retention of molecular information along the profile. Multilayered structures of the above polymers were also profiled, and it was possible to discriminate among layers having similar elemental composition but different polymer structure. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
143.
Helmstetter A 《Physical review letters》2003,91(5):058501
Using a catalog of seismicity for Southern California, we measure how the number of triggered earthquakes increases with the earthquake magnitude. The trade-off between this relation and the distribution of earthquake magnitudes controls the relative role of small compared to large earthquakes. We show that seismicity triggering is driven by the smallest earthquakes, which trigger fewer events than larger earthquakes, but which are much more numerous. We propose that the nontrivial scaling of the number of triggered earthquakes emerges from the fractal spatial distribution of seismicity. 相似文献
144.
Agnès Anne Fatima Bennani Jean-Claude Florent Jacques Moiroux Claude Monneret 《Tetrahedron letters》1985,26(22):2641-2644
The synthesis of new 3′-deamino-3′-hydroxy-daunorubicin analogs is reported and the rate of glycoside elimination under electrochemical reduction in an aprotic medium is compared to known anthracyclines. 相似文献
145.
Pommier A Stepanenko V Jarowicki K Kocienski PJ 《The Journal of organic chemistry》2003,68(10):4008-4013
An enantiospecific synthesis of the phospholipase A(2) inhibitor (+)-(4R)-manoalide is reported in which all 25 carbons of the sesterterpenoid skeleton are constructed from 3-furaldehyde, trimethylalane, oxirane, CO, beta-ionone, and propargyl bromide. The overall yield for the longest linear sequence (12 steps) is 12%. Key steps include (a) a zirconium-catalyzed carboalumination reaction to construct the C10-C11 trisubstituted alkene, (b) a Cu(I)-mediated 1,2-metalate rearrangement to construct the C6-C7 trisubstituted alkene, (c) a Sharpless kinetic resolution to secure the (4R)-stereochemistry, (d) generation of a 5-stannyl-2,3-dihydrofuran by Mo-catalyzed cycloisomerization of a homopropargylic alcohol, and (e) construction of the hydroxyfuranone ring by photooxidation of a silylfuran. 相似文献
146.
Teyssier C Marchandin H Masnou A Jeannot JL de Buochberg MS Jumas-Bilak E 《Electrophoresis》2005,26(15):2898-2907
The alpha-proteobacterial genus Ochrobactrum groups together organisms that display varied life-styles, such as free-living bacteria, members of rhizosphere and soil, nitrogen-fixing bacteria in plant nodules, xenobiotic-degrading bacteria, colonizers of nematodes and insects, and opportunistic human pathogens. The genomes of nine strains of Ochrobactrum anthropi and eight strains of Ochrobactrum intermedium were analyzed by pulsed-field gel electrophoresis of the whole genome and of I-CeuI digestion fragments. All isolates and type strains of O. anthropi and O. intermedium possessed two high-molecular-weight circular replicons identified as two independent chromosomes on the basis of 16S rDNA hybridization. The genome of the type strain of Ochrobactrum tritici, Ochrobactrum grignonense, and Ochrobactrum gallinifaecis also contained two circular chromosomes. The megaplasmid content was highly variable even among strains in the same species, leading to whole-genome sizes that ranged from 5.060 to 8.300 Mbp and from 4.690 to 7.680 Mbp for O. anthropi and O. intermedium, respectively. This exceptional level of genomic diversity could be related to the adaptability of Ochrobactrum spp. to various ecological niches. 相似文献
147.
Buré C Boujard O Bertrand M Lange C Delmas AF 《European journal of mass spectrometry (Chichester, England)》2005,11(1):31-34
Five peptide thioesters of increasing length were fragmented under two processes, in-source and in- collision cell fragmentation, using an electrospray source coupled to a triple quadrupole. Comparison of their fragmentations was made in regard to the length. The two fragmentation conditions show that the peptide length has no influence on structural information and that the fragmentation efficiency is higher for the smallest peptides than for the longest. The particularity of these peptide thioesters consists on the neutral loss of ethanethiol. The absence of the a3 fragment ion and the presence of the (a3-17) ion on the CID mass spectra are noted. 相似文献
148.
Stable, CH(2)Cl(2)-soluble mixed dodecanethiol/(amidoferrocenyl)alkanethiol (AFAT) gold colloids were synthesized by ligand substitution reactions from Brust's dodecanethiol gold colloids and the AFAT ligands to study the recognition and titration of oxoanions. Gold colloids were obtained with various chain lengths (C(11) and C(6) chains) of the AFAT ligand and different proportions of AFAT ligands in the colloids. Modification of the amidoferrocenyl structure [replacement of the free C(5)H(5) ferrocene ring by C(5)Me(5) (Cp) or C(5)H(4)COCH(3)] has been achieved to investigate the stereoelectronic effects on the recognition. The cyclic voltammetry of these colloids in CH(2)Cl(2) on Pt electrode shows a reversible Fe(II/III) wave with some adsorption. With AFAT ligands, a new, less electrochemically reversible wave (with some adsorption) at a potential 220 +/- 20 mV less positive than that of the initial wave appears upon titration of [n-Bu(4)N][H(2)PO(4)], and the initial wave completely disappears after addition of 1 equiv of anion, which allows its titration. The potential shift does not depend on the AFAT proportion nor on its chain length but is reduced with Cp and enhanced with C(5)H(4)COCH(3), showing the key role of the hydrogen bonding between the -NH-amido group and a terminal oxygen atom of the oxoanions. According to the Echegoyen-Kaifer model, the potential shift leads to the ratio K((+))/K((0)) of apparent association constants. In the presence of both [n-Bu(4)N][HSO(4)] and [n-Bu(4)N]Cl, a shift of the initial wave (rather than its replacement) allows an easy titration, ideally with 20-Fc. Upon addition of [n-Bu(4)N][HSO(4)] alone, a weak wave shift (30 mV) of the colloids is also observed, allowing the titration of the HSO(4)(-) anion by the colloids containing a low percentage of AFAT ligand. The Echegoyen-Kaifer model provides access to the apparent association constant K((+)) in this case for which the interaction between the anion and the neutral form of the host is not significant. With the C(5)H(4)COCH(3) modification of the amidoferrocenyl branch, a new wave appears at a potential 70 mV more positive than the initial wave, signifying a stronger interaction with this modified ligand than with the parent AFAT ligand. These colloids favorably compare with ferrocenyl dendrimers in terms of rapid synthesis and selectivity of H(2)PO(4-) over HSO(4-) and with gold surfaces for the recognition of HSO(4)(-). 相似文献
149.
Moloney Mícheál P. Massoni Nicolas Grandjean Agnès 《Journal of Thermal Analysis and Calorimetry》2021,145(5):2353-2362
Journal of Thermal Analysis and Calorimetry - It is well known that the physical properties of nanoparticles can be tuned by controlling synthetic factors such as pH, temperature, reactant ratio or... 相似文献
150.
New off-line instrumentation was developed to implement measurements of non-methane hydrocarbons (NMHC) on (French) research
aircraft. NMHC are collected on multisorbent tubes by AMOVOC (Airborne Measurements Of Volatile Organic Compounds), a new
automatic sampler. AMOVOC is a versatile and portable sampler targeting a wide range of NMHC at high frequency (sampling time
of 10 min). Multisorbent tubes are analyzed on the ground by short-path thermal desorption coupled with gas chromatography
and mass spectrometry. The development and optimization of both NMHC sampling and analysis are reported here. On the one hand,
the paper points out technical choices that were made according to aircraft constraints and avoiding sample loss or contamination.
On the other hand, it describes analytical optimization, tube storage stability, and moisture removal. The method shows high
selectivity, sensitivity (limit of detection less than 10 ppt) and precision (less than 24%). Finally, NMHC data collected
on French aircraft during the African Monsoon Multidisciplinary Analysis campaign are reported for the first time. The results
highlight instrumentation validity and protocol efficiency for NMHC measurements in the lower and upper troposphere. 相似文献