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991.
The energy levels of the 5f configuration of U(5+) and 5f(2) configuration of U(4+) have been calculated in a dressed effective Hamiltonian relativistic spin-orbit configuration interaction framework. Electron correlation is treated in the scalar relativistic scheme with either the multistate multireference second-order multiconfigurational perturbation theory (MS-CASPT2) or with the multireference single and double configuration interaction (MRCI) and its size-extensive Davidson corrected variant. The CASPT2 method yields relative energies which are lower than those obtained with the MRCI method, the differences being the largest for the highest state (1)S(0) of the 5f(2) manifold. Both valence correlation effects and spin-orbit polarization of the outer-core orbitals are shown to be important. The satisfactory agreement of the results with experiments and four-component correlated calculations illustrates the relevance of dressed spin-orbit configuration interaction methods for spectroscopy studies of heavy elements. 相似文献
992.
Pellerin N Dodane-Thiriet C Montouillout V Beauvy M Massiot D 《The journal of physical chemistry. B》2007,111(44):12707-12714
MgAl2O4 and ZnAl2O4 spinels have been irradiated by swift heavy ions (86Kr and 36S) simulating the irradiation by fission products for applications in the transmutation targets. The structures of unirradiated and irradiated spinel samples have been studied by NMR spectroscopy, with 27Al magic angle spinning and multiple-quantum magic angle spinning experiments. The parameters of fluence and electronic stopping power have been compared. For 86Kr ions, the obtained spectra are modified by irradiation: we observe a rise of the amount of aluminum in tetrahedral sites and a widening of the lines associated with the different aluminum environments compared with those of the pristine samples. Site exchange in the cationic sublattice is then observed and can be quantified from NMR spectra, determining the inversion parameter. An inversion parameter of 0.77 is estimated for the MgAl2O4 spinel irradiated with 1013 Kr ions/cm2, for a value of 0.275 in the pristine samples. Moreover, a line attributed to aluminum in 5-fold coordination with oxygen is observed in irradiated spinel samples at the maximum fluence for krypton. These new aluminum environments can characterize a transition layer which could change toward an amorphous layer, increasing the electronic stopping power and/or the fluence. 相似文献
993.
Bolivianine, a novel sesterpene with an unprecedented skeleton, has been isolated from the trunk bark of Hedyosmum angustifolium (Chloranthaceae), with isobolivianine, an isomer formed under acidic conditions. The structure and relative stereochemistry were elucidated on the basis of spectroscopic data. A hypothesis for biogenesis was made. 相似文献
994.
995.
Brenner V Piuzzi F Dimicoli I Tardivel B Mons M 《The journal of physical chemistry. A》2007,111(31):7347-7354
Aminoisobutyric acid (Aib) is a synthetic amino acid known to favor the formation of 3(10) helical structures in condensed phases, namely, crystals. The intrinsic character of these helicogenic properties has been investigated on the Ac-Aib-Phe-Aib-NH2 molecule under isolated conditions, namely, in the gas phase, both experimentally by double-resonance IR/UV spectroscopy and theoretically by quantum chemistry. A convergent set of evidence, based on energetic, IR, and UV spectroscopic data as well as on analogies with the similar peptide Ac-Ala-Phe-Ala-NH2 previously studied, enables us to conclude the formation of an incipient 310 helix in these isolated systems. 相似文献
996.
Jacquemin D Wathelet V Preat J Perpète EA 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,67(2):334-341
The UV/vis absorption spectra of 101 anthraquinones solvated in two protic solvents (methanol and ethanol) has been theoretically predicted using the time-dependent density functional theory (TD-DFT) for the excited state calculations and the polarizable continuum model (PCM) for evaluating bulk solvent effects. Two functionals (B3LYP and PBE0) have been used and they provide similar mean absolute deviations (approximately 0.09 eV) but mean signed errors presenting opposite signs. The errors can be minimized by using simple or multiple linear regression, the latter combining the results of both functionals to reach an optimal estimation of the lambda(max) (mean absolute error 0.06 eV). Specific fittings for the two media have been performed and it turned out that our approach is even more efficient for anthraquinones solvated in ethanol. 相似文献
997.
Dr. Annalisa Pierro Dr. Alessio Bonucci Dr. Davide Normanno Dr. Mireille Ansaldi Dr. Eric Pilet Prof. Olivier Ouari Prof. Bruno Guigliarelli Dr. Emilien Etienne Dr. Guillaume Gerbaud Dr. Axel Magalon Prof. Valérie Belle Dr. Elisabetta Mileo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(66):e202202249
One of the greatest current challenges in structural biology is to study protein dynamics over a wide range of timescales in complex environments, such as the cell. Among magnetic resonances suitable for this approach, electron paramagnetic resonance spectroscopy coupled to site-directed spin labeling (SDSL-EPR) has emerged as a promising tool to study protein local dynamics and conformational ensembles. In this work, we exploit the sensitivity of nitroxide labels to report protein local dynamics at room temperature. We demonstrate that such studies can be performed while preserving both the integrity of the cells and the activity of the protein under investigation. Using this approach, we studied the structural dynamics of the chaperone NarJ in its natural host, Escherichia coli. We established that spin-labeled NarJ is active inside the cell. We showed that the cellular medium affects NarJ structural dynamics in a site-specific way, while the structural flexibility of the protein is maintained. Finally, we present and discuss data on the time-resolved dynamics of NarJ in cellular context. 相似文献
998.
Crozet Marielle Demeyer Séverine Lourenço Valérie Herranz Margarita Boden Sven 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(7):2967-2982
Journal of Radioanalytical and Nuclear Chemistry - INSIDER (Improved Nuclear SIte characterization for waste minimization in D&D operations under constrained EnviRonment) was a European... 相似文献
999.
1000.
Christophe Detrembleur Jean‐Louis Clément Valérie Sciannaméa Christine Jérôme Jean‐Marie Catala Didier Gigmes Laurent Autissier Edith Botek Natalia Zarycz Benoît Champagne 《Journal of polymer science. Part A, Polymer chemistry》2013,51(8):1786-1795
The styrene polymerization initiated by benzoyl peroxide (BPO) in the presence of N‐tert‐butyl‐α‐isopropylnitrone as nitroxide precursor is well‐controlled provided that a prereaction between the nitrone and BPO is carried out in suitable conditions prior to polymerization at a higher temperature. Electron spin resonance (ESR) spectroscopy was implemented to probe the nitroxides formed during both steps, that is, the prereaction and polymerization, and to get crucial information regarding the structure of the nitroxides responsible for the polymerization control. ESR studies combined with first principles calculations have evidenced that nitroxides observed during the prereaction in the presence of styrene and during the polymerization steps consist of a mixture of two macronitroxides. One is formed by the addition of a growing polystyrene chain to the nitrone as would be expected. However, the second one results from the addition of a polystyrene chain to tert‐butyl nitroso that is in situ formed presumably by decomposition of the first macronitroxide type. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 相似文献