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101.
Suzuki D Kato H Ohkawa M Anzai K Tanaka H Limão-Vieira P Campbell L Brunger MJ 《The Journal of chemical physics》2011,134(6):064311
We report measurements of differential and integral cross sections for electron excitation of the Schumann-Runge continuum, longest band, and second band electronic states in molecular oxygen. The energy range of the present study is 15-200 eV, with the angular range of the differential cross section (DCS) measurements from 2 to 130°. A generalized oscillator strength analysis is then employed in order to derive integral cross sections (ICSs) from the corresponding DCSs, and these ICSs are compared with relevant energy and oscillator strength scaled Born cross section (BEf-scaling [Y.-K. Kim, J. Chem. Phys. 126, 064305 (2007)]) results determined as a part of this investigation. Interestingly, while the present Schumann-Runge continuum and second band ICSs were in reasonable agreement with the respective BEf-scaling results, agreement for the longest band was poor below 100 eV with a possible reason for this apparently anomalous behavior being canvassed here. Finally, where possible all present data are compared with the results from earlier measurements and calculations with the level of agreement found being very good in some cases and marginal in others. 相似文献
102.
Giganti VG Kundoor S Best WA Angel LA 《Journal of the American Society for Mass Spectrometry》2011,22(2):300-309
Ion mobility-mass spectrometry is used to study the new conformers of bovine ubiquitin (Ub) and the palladium(II) binding
sites after the incubation with cis-[Pd(en)(H2O)2]2+ where en = ethylenediamine. Palladium(II) complexes are potentially useful proteomic reagents because they selectively bind
to the side groups of methionine and histidine and hydrolytically cleave the peptide bond. Incubating 1.0 mM solution of Ub
with 10.0 molar excess of cis-[Pd(en)(H2O)2]2+ results with one to four Pd2+ or Pd(en)2+ being attached to intact Ub and two conformer families at each of the 4+ to 11+ charge states. The 4+ and 5+ species exhibit
a compact form, which is also observed in untreated Ub, and a new highly folded conformer. The 6+ to 10+ exhibit an elongated
form, also observed in Ub, and a new partially folded conformer. The new conformers are shown to be more stable if they contain
at least one Pd2+, rather than all Pd(en)2+. IM-MS/MS of [UbPd2en+5H]9+ shows that both the partially folded and elongated conformers first lose the en ligand, followed by dissociating into product
ions that indicate that Met1, Glu51/Asp52, His68, and Glu16 are binding sites for Pd2+. These results suggest that Pd2+ is simultaneously binding to multiple side groups across different regions of Ub. This type of sequestering of Pd2+ probably reduces the efficiency of Pd2+ ions to selectively cleave Ub because it prevents Pd2+ anchoring to only Met or His and to an adjacent backbone amide nitrogen and forming the “activated complex” necessary for
specific peptide bond cleavage. 相似文献
103.
Mikhalyova EA Kolotilov SV Zeller M Thompson LK Addison AW Pavlishchuk VV Hunter AD 《Dalton transactions (Cambridge, England : 2003)》2011,40(41):10989-10996
Two lanthanide tetrafluoro-p-phthalate (L(2-)) complexes, Ln(L)(1.5)·DMF·H(2)O (Ln = Pr(3+) (1), Nd(3+) (2)), were synthesized using pyridine as a base. The compounds were found to be isostructural, and the structure of 1 has been determined by single crystal X-ray diffraction (monoclinic, space group C2, a = 22.194(2) ?, b = 11.4347(12) ?, c = 11.7160(12) ?, β = 94.703(2)°, V = 2963.3(5) ?(3), Z = 4). The crystal structure of 1 consists of dinuclear Pr(3+) units, which are connected by tetrafluoro-p-phthalate, forming separate 2D polymeric layers. The Ln(3+) ions in the dinuclear Ln(2) units are linked by two μ-O atoms and by two bridging O-C-O groups. The structure is porous with DMF and water molecules located between layers. Non-coordinated DMF molecules occupy about 27% of the unit cell volume. A systematic analysis of reported structures of Ln(III) polymers with p-phthalate and its derivatives shows that the ca. known 60 structures can be divided into six possible structural types depending on the presence of certain structural motifs. The magnetic properties of compounds 1 and 2 were studied. The dependence of χ(M)T on T (where χ(M) is magnetic susceptibility per dinuclear lanthanide unit) for 1 and 2 was simulated using two different models, based on: (i) the Hamiltonian ? = Δ?(z)(2)+ μ(B)g(J)H?, which utilises an axial splitting parameter Δ and temperature-independent paramagnetism (tip) and (ii) crystal field splitting. It was found that both models gave satisfactory fits, indicating that the Ln-Ln exchange interactions are small and the symmetry of the coordination environment is the main factor influencing the magnetic properties of these compounds. 相似文献
104.
Tandon SS Dul MC Lee JL Dawe LN Anwar MU Thompson LK 《Dalton transactions (Cambridge, England : 2003)》2011,40(14):3466-3475
Ligands based on carbo- and thio-carbohydrazone cores, modified with pyridine, carboxylate and oxime ends, have been examined. They display a tautomeric versatility based on the flexible nature of the hydrazone linkages, leading to varied coordination motifs. Examples of mononuclear (Co(II), Ni(II)), dinuclear (Co(III)), 1D chain (Cu(II)) and square [2 × 2] grid (Ni(II)) complexes are obtained. Ferromagnetic (Cu(II)) and antiferromagnetic (Ni(II)) exchange is observed, with spin coupling in the Ni(II)(4) square grids propagated through the μ-O and μ-S bridges. Weak antiferromagnetic exchange (J = -6.0 cm(-1)) is observed for the μ-O bridged grid, despite the large Ni-O-Ni angles (137-141°), while for the μ-S bridged grids much stronger exchange is observed (J = -148 cm(-1), -198 cm(-1)). This is much larger than expected based on the Ni-S-Ni bridge angles (151-169°), and is associated with the soft (less polarizing than oxygen) nature of the sulfur bridge, which would allow for much more efficient transmission of spin exchange than observed in the μ-O bridged case. Structures and variable temperature magnetic data are included, and spin exchange is analyzed using normal Heisenberg exchange models. No examples involving oxime (NO) bridging are reported, which reflects the positioning of the N,O and N,S donor combinations in each ligand, and the preferred coordination through these donor atoms. 相似文献
105.
The radical carbozincation of diethyl acetylenedicarboxylate, performed at room temperature in the presence of air, leads to fumaric derivatives through a selective alkylzinc group radical transfer controlled by coordination. The total trans stereocontrol is unprecedented, carbocupration is well-known to give the reversal selectivity at low temperature, while classical radical addition methodologies lead to mixtures of isomers. 相似文献
106.
107.
Furans may be ring opened via pallado-catalyzed reactions leading to α,β-unsaturated aldehydes and ketones tethered to indole and isoquinoline moieties. Besides their synthetic interest, these fragmentations bring interesting elements into the discussion around the reaction mechanisms involved in palladium C-H activations of electron-rich heterocycles. 相似文献
108.
Merten C Barron LD Hecht L Johannessen C 《Angewandte Chemie (International ed. in English)》2011,50(42):9973-9976
Splitting it up: Excellent agreement between the experimental and the quantum-chemically simulated Raman optical activity (ROA) spectrum of (+)-poly(trityl methacrylate) shows that the polymer backbone adopts a left-handed helical conformation while the trityl side groups display a left-handed propeller conformation. Thus ROA can be used to determine the complete structure of synthetic chiral polymers in solution. 相似文献
109.
The lithium-oxygen battery with ether-based electrolytes 总被引:4,自引:0,他引:4
Freunberger SA Chen Y Drewett NE Hardwick LJ Bardé F Bruce PG 《Angewandte Chemie (International ed. in English)》2011,50(37):8609-8613
110.
We introduce active, probe-based microrheological techniques for measuring the flow and deformation of complex fluids. These techniques are ideal for mechanical characterization either when little sample is available, or when samples show significant spatial heterogeneity. We review recent results, paying particular attention to comparing and contrasting rheological parameters obtained from micro- and macro-rheological techniques. 相似文献