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951.
Y Q Xia C E Hop D Q Liu S H Vincent S H Chiu 《Rapid communications in mass spectrometry : RCM》2001,15(22):2135-2144
A method with parallel extraction columns and parallel analytical columns (PEC-PAC) for on-line high-flow liquid chromatography/tandem mass spectrometry (LC/MS/MS) was developed and validated for simultaneous quantification of a drug candidate and its six metabolites in dog plasma. Two on-line extraction columns were used in parallel for sample extraction and two analytical columns were used in parallel for separation and analysis. The plasma samples, after addition of an internal standard solution, were directly injected onto the PEC-PAC system for purification and analysis. This method allowed the use of one of the extraction columns for analyte purification while the other was being equilibrated. Similarly, one of the analytical columns was employed to separate the analytes while the other was undergoing equilibration. Therefore, the time needed for re-conditioning both extraction and analytical columns was not added to the total analysis time, which resulted in a shorter run time and higher throughput. Moreover, the on-line column extraction LC/MS/MS method made it possible to extract and analyze all seven analytes simultaneously with good precision and accuracy despite their chemical class diversity that included primary, secondary and tertiary amines, an alcohol, an aldehyde and a carboxylic acid. The method was validated with the standard curve ranging from 5.00 to 5000 ng/mL. The intra- and inter-day precision was no more than 8% CV and the assay accuracy was between 95 and 107%. 相似文献
952.
953.
R. A. Sawyer H. B. Vincent H. V. Knorr V. M. Albers G. N. Thomis W. V. Thorpe R. T. Williams und L. Kulberg 《Fresenius' Journal of Analytical Chemistry》1940,120(1-2):21-22
Ohne Zusammenfassung 相似文献
954.
Dr. Logesh Mathivathanan Dr. Guillaume Rogez Dr. Nadia Ben Amor Prof. Vincent Robert Prof. Raphael G. Raptis Dr. Athanassios K. Boudalis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(56):12769-12784
Previously reported ferromagnetic triangles (NnBu4)2[Cu3(μ3-Cl)2(μ-4-NO2-pz)3Cl3] ( 1 ), (PPN)2[Cu3(μ3-Cl)2(μ-pz)3Cl3] ( 2 ), (bmim)2[Cu3(μ3-Cl)2(μ-pz)3Cl3] ( 3 ) and newly reported (PPh4)2[Cu3(μ3-Cl)2(μ-4-Ph-pz)3Cl3] ( 4 ) were studied by magnetic susceptometry, electron paramagnetic resonance (EPR) spectroscopy and ab initio calculations to assess the origins of their ferromagnetism and of the magnetic anisotropy of their ground S=3/2 state (PPN+=bis(triphenylphosphine)iminium, bmim+=1-butyl-3-methylbenzimidazolium, pz−=pyrazolate). Ab initio studies revealed the d character of the magnetic orbitals of the compressed trigonal bipyramidal copper(II) ions. Ferromagnetic interactions were attributed to weak orbital overlap via the pyrazolate bridges. From the wavefunctions expansions, the ratios of the magnetic couplings were determined, which were indeterminate by magnetic susceptometry. Single-crystal EPR studies of 1 were carried out to extend the spin Hamiltonian with terms which induce zero-field splitting (zfs), namely dipolar interactions, anisotropic exchange and Dzyaloshinskii–Moriya interactions (DMI). The data were treated through both a giant-spin model and through a multispin exchange-coupled model. The latter indicated that ≈62 % of the zfs is due to anisotropic and ≈38 % due to dipolar interactions. The powder EPR data of all complexes were fitted to a simplified form of the multispin model and the anisotropic and dipolar contributions to the ground state zfs were estimated. 相似文献
955.
Dr. Fa-Jie Chen Dr. Mengmeng Zheng Vincent Nobile Dr. Jianmin Gao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(20):e202200058
This work reports a novel chlorooxime mediated modification of native peptides and proteins under physiologic conditions. This method features fast reaction kinetics (apparent k2=306±4 M−1s−1 for GSH) and exquisite selectivity for cysteine residues. This cysteine conjugation reaction can be carried out with just single-digit micromolar concentrations of the labeling reagent. The conjugates show high stability towards acid, base, and external thiol nucleophiles. A nitrile oxide species generated in situ is likely involved as the key intermediate. Furthermore, a bis-chlorooxime reagent is synthesized to enable facile Cys-Cys stapling in native peptides and proteins. This highly efficient cysteine conjugation and stapling was further implemented on bacteriophage to construct chemically modified phage libraries. 相似文献
956.
Jing Zhang Dr. Astrid Schaly Dr. Jean-Claude Chambron Dr. Bruno Vincent Nathalie Zorn Dr. Emmanuelle Leize-Wagner Marion Jean Dr. Nicolas Vanthuyne 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(7):e202103759
Chiral gold(I) acetylide trinuclear complexes 1 – 3 based on the cyclotribenzylene platform and terminal PR3 ligands (R=Ph, Et, and Cy, respectively), were characterized and their light emission studied. They exhibited long-lived blue phosphorescence in CHCl3 and a weak fluorescence in the UV. In MeOH/CHCl3 mixtures of >1:1 volume ratio, 1 and 2 exhibited a new emission band at ca. 540 nm that developed at the expense of the UV emission. DLS studies demonstrated the presence of molecular aggregates of Ø 30–80 nm. The green emission observed in MeOH-rich solvent mixtures was therefore induced by aggregation, and could originate from Au⋅⋅⋅Au interactions. The AIE spectrum of 3 was observed only in solutions containing 99 % of MeOH, and correlated with its solid state emission. The AIE profiles of the enantiomers of 1 differed from that of rac- 1 , suggesting that the latter is a true racemate. 相似文献
957.
The tetrahydroisoquinoline (THIQ) moiety forms the backbone of several natural, synthetic, and semisynthetic drugs approved for the treatment of cancer, pain, gout, and various neurodegenerative diseases. Plants synthesize up to 3000 THIQ structures constituting the benzylisoquinoline, phenethylisoquinoline, Amaryllidaceae, and ipecac alkaloid classes. This review outlines the ongoing surge in activity surrounding the production of natural, semisynthetic, and new-to-nature THIQ metabolites in engineered microbial systems. These efforts have accelerated THIQ pathway discovery and engineering, unlocked new domains of chemical space, and spurred the development of highly productive microbial strains synthesizing unprecedented yields of THIQ precursors. Consolidating these advancements into a single bioprocess holds potential to outcompete crop-based manufacturing and total synthesis for the production of high-value THIQ pharmaceuticals at scale. 相似文献
958.
959.
Mark A. Vincent Arnaldo F. Silva Paul L. A. Popelier 《Journal of computational chemistry》2019,40(32):2793-2800
Recently, the quantum topological energy partitioning method called interacting quantum atoms (IQA) has been extended to MPn (n = 2, 3, 4) wave functions. This enables the extraction of chemical insight related to dynamic electron correlation. The large computational expense of the IQA-MPn approach is compensated by the advantages that IQA offers compared to older nontopological energy decomposition schemes. This expense is problematic in the construction of a machine learning training set to create kriging models for topological atoms. However, the algorithm presented here markedly accelerates the calculation of atomically partitioned electron correlation energies. Then again, the algorithm cannot calculate pairwise interatomic energies because it applies analytical integrals over whole space (rather than over atomic volumes). However, these pairwise energies are not needed in the quantum topological force field FFLUX, which only uses the energy of an atom interacting with all remaining atoms of the system that it is part of. Thus, it is now feasible to generate accurate and sizeable training sets at MPn level of theory. © 2019 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc. 相似文献
960.
Robert J. Messinger Tan Vu Huynh Renaud Bouchet Vincent Sarou-Kanian Michaël Deschamps 《Magnetic resonance in chemistry : MRC》2020,58(11):1118-1129
Magic-angle-spinning (MAS) enhances sensitivity and resolution in solid-state nuclear magnetic resonance (NMR) measurements. MAS is obtained by aerodynamic levitation and drive of a rotor, which results in large centrifugal forces that may affect the physical state of soft materials, such as polymers, and subsequent solid-state NMR measurements. Here, we investigate the effects of MAS on the solid-state NMR measurements of a polymer electrolyte for lithium-ion battery applications, poly(ethylene oxide) (PEO) doped with the lithium salt LiTFSI. We show that MAS induces local chain ordering, which manifests itself as characteristic lineshapes with doublet-like splittings in subsequent solid-state 1 H, 7 Li, and 19 F static NMR spectra characterizing the PEO chains and solvated ions. MAS results in distributions of stresses and hence local chain orientations within the rotor, yielding distributions in the local magnetic susceptibility tensor that give rise to the observed NMR anisotropy and lineshapes. The effects of MAS were investigated on solid-state 7 Li and 19 F pulsed-field-gradient (PFG) diffusion and 7Li longitudinal relaxation NMR measurements. Activation energies for ion diffusion were affected modestly by MAS. 7Li longitudinal relaxation rates, which are sensitive to lithium-ion dynamics in the nanosecond regime, were essentially unchanged by MAS. We recommend that NMR researchers studying soft polymeric materials use only the spin rates necessary to achieve the desired enhancements in sensitivity and resolution, as well as acquire static NMR spectra after MAS experiments to reveal any signs of stress-induced local ordering. 相似文献