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71.
Conerney B Jensen P Kruger PE MacGloinn C 《Chemical communications (Cambridge, England)》2003,(11):1274-1275
The synthesis and structural characterisation of a novel C3-symmetric tris-bidentate ligand, L, featuring a triphenylamine core appended by pyridylimine coordination sites is reported: 1H NMR compleximetric titration studies with Ag(I) and ESMS indicate the presence of [Ag3L2]3+ species in solution, consistent with the formation of a trinuclear double helicate complex: the Trinity helix. 相似文献
72.
It is demonstrated that the upper and lower values of a two-person, zero-sum differential game solve the respective upper and lower Isaacs' equations in the viscosity sense (introduced by Crandall and Lions (Trans. Amer. Math. Soc. 277 (1983), 1–42). Since such solutions are unique, this yields a fairly simple proof that the game has value should the minimax condition hold. As a further application of viscosity techniques, a new and simpler proof that the upper and lower values can be approximated by the values of certain games with Lipschitz controls is given. 相似文献
73.
Nicolas Eugster Henrik Jensen David J. Fermín Hubert H. Girault 《Journal of Electroanalytical Chemistry》2003,560(2):143-149
The self-organisation of a variety of dyes at the water|1,2-dichloroethane interface was studied by admittance measurements, photocurrent–potential curves and light polarisation anisotropy of the photocurrent. The heterogeneous photo-oxidation of ferrocene was studied at interfaces sensitised by Sn(IV) meso-tetra-(4-carboxyphenyl) porphyrin dichloride (SnTPPC), chlorin e-6, protoporphyrin IX (protoIX) and Fe(III) protoporphyrin IX chloride (Fe-protoIX). Cyclic voltammograms and capacitance voltage curves exhibit different features associated with the self-assembly of the dye species at the liquid|liquid boundary. In the case of SnTPPC, the capacitance curves displayed the characteristic responses commonly associated with the specific adsorption of ionic species. On the other hand, chlorin e-6, protoIX and Fe-protoIX show rather complex behaviour suggesting not only changes in the excess charge but also in the dielectric permittivity of the interface. Differences in the photocurrent efficiency were also observed under the same experimental conditions. The relative magnitude of the photocurrent responses were rationalised in terms of the phenomenological electron transfer rate constant, the photon capture cross-sections and the lifetime of the triplet state as obtained from nanosecond flash photolysis. Finally, the average molecular orientation of the adsorbed photoactive species was estimated from the photocurrent dependence on the angle of light polarisation in total internal reflection. The results show a clear correlation between the orientation of the transition dipole and the distribution of the peripheral carboxyl groups responsible for the hydrophilic nature of the dyes. 相似文献
74.
Frank Jensen 《Journal of computational chemistry》1994,15(11):1199-1216
A previously proposed method of modeling force field transition structures as the lowest energy structure on the seam of two intersecting potential energy surfaces is improved with respect to the force field expression and the efficiency of the optimization algorithm. Comparison with ab initio and experimental results show that the force field method may have the potential of achieving almost quantitative results. It appears that the results from transition state modeling are currently limited by the accuracy of the underlying force field. © 1994 by John Wiley & Sons, Inc. 相似文献
75.
Brajagopal Samanta Joy Chakraborty C. R. Choudhury S. K. Dey D. K. Dey S. R. Batten P. Jensen Glenn P. A. Yap Samiran Mitra 《Structural chemistry》2007,18(1):33-41
We have reported herein the synthesis of three new Cu(II) complexes of tri- and tetradentate Schiff base ligands containing
N3 or N4 donor set along with terminal NNN− or SCN− ligands: [L1Cu(NCS)]ClO4 (1), [L2Cu(NCS)2] (2) and [L3Cu(NNN)]ClO4 (3) [L1 = NC5H4C(CH3)=N(CH2)3N=C(CH3)C5H4N, L2= Me2N–(CH2)3–N=C(CH3)C5H4N and L3 = NC5H4CH=N–(CH2)4–N=CHC5H4N]. The complexes have been systematically characterised by elemental, spectroscopic and electrochemical techniques. Antimicrobial
activities of the Schiff base ligands and their metal complexes have been studied using the disc diffusion method on the strains
of Candida tropicalis and Bacillus megaterium. Structures of all the complexes have been unequivocally established from single crystal X-ray diffraction analyses that
show the monomeric units containing a five-coordinated copper center in highly distorted square pyramidal geometry with thiocyanate
or azide anion coordinated as terminal ligand. The complexes 1 and 3 crystallise in monoclinic (P21/c) and 2 in triclinic (P-1) space group, respectively. 相似文献
76.
A comparative study has been undertaken on various strong anion-exchangers to investigate the pH dependence, titration curves, efficiency, binding strength, and dynamic capacity of the chromatographic resins. The resins tested included: Macro-Prep 25Q, TSK-Gel Q-5PW-HR, Poros QE/M, Q Sepharose FF, Q HyperD 20, Q Zirconia, Source 30Q, Fractogel EMD TMAE 650s, and Express-Ion Q. Testing was performed with five different proteins: Anti-FVII Mab (IgG), aprotinin, BSA, lipolase, and myoglobin. The dependence of pH on retention varies from generally low to very high for proteins with low pI. No direct link between pH dependence on retention and titration curves of the different resins was observed. Efficiency results show the expected trend of lower dependence of the plate height with increasing flow-rate of resins for medium and high pressure operation compared to the soft resins. Binding to the anion-exchange resins as a function of ionic strength may vary depending on the specific protein. Generally, binding and elution at a high salt concentration may be performed with Poros QE/M or Macro-Prep 25Q, while binding and elution at low salt concentration may be done with TSK-Gel Q-5PW. Dynamic capacities are strongly dependent on the specific protein employed and for some resins dependent on the flow-rate. A general good agreement was obtained between this study and data obtained by suppliers for the dynamic capacity. The results of this study may be used for selection of resins for testing in process development, however, the data does not tell anything about specific selectivity differences or resolution between a target protein and a given impurity. None of the resins studied here should be regarded as good or bad, but more or less suitable for a specific purpose, and only testing for the specific application will determine which one is the optimal resin. 相似文献
77.
A comparative study was performed on strong anion exchangers to investigate the pH dependence, titration curves, efficiency, binding strength, particle size distribution, and static and dynamic capacity of the chromatographic resins. The resins tested included Q Sepharose XL, UNO Q-1, Poros 50 HQ, Toyopearl QAE 550c, Separon HemaBio 1000Q, Q-Cellthru Bigbeads Plus, Q Sepharose HP and Toyopearl SuperQ 650s. Testing was performed with five different proteins: anti-Factor VII monoclonal antibody (immunoglobulin G), aprotinin, bovine serum albumin, lipolase and myoglobin. The dependence of pH on retention varies from generally low to very high for proteins with a low isoelectric point (pl). An unexpected binding at pH 7-8 of aprotinin with pI >11 was observed on Separon HemaBio 1000Q. No link between pH dependence on retention and titration curves of the different resins was observed. Efficiency results show the expected trend of higher dependence of the plate height with increasing flow-rate of soft resins compared to resins for medium- and high-pressure operation. No or a very small difference in particle size distribution was obtained between new and used resins. Binding to anion-exchange resins as a function of ionic strength varies to some extent depending on the specific protein. Generally, binding and elution at high salt concentration may be performed with Q Sepharose XL, Toyopearl QAE 550c, Q Sepharose HP and Poros 50 HQ, while binding and elution at low salt concentration may be performed with Q-Cellthru Bigbeads Plus. A very high binding capacity was obtained with Q Sepharose XL. Comparison of static capacity and dynamic capacity at 10% breakthrough shows approx. 50-80% utilization of the total available capacity during chromatographic operation. A general good agreement was obtained between this study and data obtained by the suppliers. The results of this study may be used for selection of resins for testing in process development. 相似文献
78.
Sullens TA Jensen RA Shvareva TY Albrecht-Schmitt TE 《Journal of the American Chemical Society》2004,126(9):2676-2677
Novel open-framework alkali metal uranyl periodates, having the formula A[(UO2)3(HIO6)(OH)(O)(H2O)].1.5H2O (A = Li, Na, K, Rb, Cs), have been prepared through mild hydrothermal synthesis. These isostructural compounds contain distorted UO7 pentagonal bipyramids that are linked through a uranyl (UO22+) to uranyl cation-cation interaction. This interaction arises from a single axial uranyl oxygen coordinating at an equatorial site of an adjacent uranyl unit. These uranium oxide polyhedra are further bound by IO6 distorted octahedra creating an open-framework structure whose channels contain the alkali metal cations. 相似文献
79.
Ab initio coupled cluster calculations with single and double substitutions and a perturbative treatment of connected triple excitations [CCSD(T)] with the augmented correlation-consistent polarized valence triple-zeta aug-cc-pVTZ basis at 51 816 geometries provide a six-dimensional potential-energy surface for the electronic ground state of NH3. At 3814 selected geometries, CBS+ energies are obtained by extrapolating the CCSD(T) results for the aug-cc-pVXZ(X=T,Q,5) basis sets to the complete basis set (CBS) limit and adding corrections for core-valence correlation and relativistic effects. CBS** ab initio energies are generated at 51,816 geometries by an empirical extrapolation of the CCSD(T)/aug-cc-pVTZ results to the CBS+ limit. They cover the energy region up to 20,000 cm-1 above equilibrium. Parametrized analytical functions are fitted through the ab initio points. For these analytical surfaces, vibrational term values and transition moments are calculated by means of a variational program employing a kinetic-energy operator expressed in the Eckart-Sayvetz frame. Comparisons against experiment are used to assess the quality of the generated potential-energy surfaces. A "spectroscopic" potential-energy surface of NH3 is determined by a slight empirical adjustment of the ab initio potential to the experimental vibrational term values. Variational calculations on this refined surface yield rms deviations from experiment of 0.8 cm-1 for 24 inversion splittings and 0.4 (3.0) cm-1 for 34 (51) vibrational term values up to 6100 (10,300) cm-1. 相似文献
80.
Ravn P Kjaer S Jensen KH Wind T Jensen KB Kristensen P Brosh RM Orren DK Bohr VA Clark BF 《Electrophoresis》2000,21(3):509-516
A procedure was established for selecting phage antibodies (phage-abs) from phage-displayed antibody repertoires by panning against proteins, separated by sodium dodecyl phosphate-polyacrylamide gel electrophoresis (SDS-PAGE) and electroblotted onto nitrocellulose membranes (Western blots). This immobilization strategy is applicable for secondary rounds of panning in selections against semipurified proteins, and directs the selection toward antibodies suitable as immunochemical reagents in Western blots. In model experiments, enrichment factors as high as 1.9x10(5) were obtained in a single round of panning. Furthermore, we demonstrate the application of this approach by selection of phage-abs recognizing the human Werner protein, which is defective in a premature aging syndrome. 相似文献