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51.
Ionic conductivity of electroporated lipid bilayer membranes 总被引:1,自引:0,他引:1
52.
The development of an amperometric biosensor for the determination of phenolic compounds is described, using quinoprotein glucose dehydrogenase. The enzyme is integrated into carbon paste and its ability to donate electrons to oxidized phenolic compounds during glucose oxidation is exploited. The sensor response is based on electrochemical oxidation of the phenolic compound followed by its enzymatic regeneration when the bulk solution contains glucose and the electrode is potentiostated at +500 mV (vs. Ag/AgCl/0.1 mol/L KCl). As the result of the catalytic analyte regeneration the electrodes offer very sensitive measurements of redox species like p-aminophenol and hydroquinone and catecholamines such as epinephrine, norepinephrine, and dopamine. The sensor performance is characterized for the different substrates. Highest sensitivity is achieved for p-aminophenol which could be determined at sub-nanomolar level. 相似文献
53.
The mixed‐valent oxotantalate Eu1.83Ta15O32 was prepared from a compressed mixture of Ta2O5 and the metals in a sealed Ta ampoule at 1400 °C. The crystal structure was determined by means of single crystal X‐ray diffraction: space group R3¯, a = 777.2(6) pm and c = 3523.5(3) pm, Z = 3, 984 symmetrically independent reflections, 83 variables, RF = 0.027 for I > 2σ (I). The structure is isotypic to Ba2Nb15O32. The salient feature is a [Ta(+8/3)6O12iO6a] cluster consisting of an octahedral Ta6 core bonded to 12 edge‐bridging inner and six outer oxygen atoms. The clusters are arranged to slabs which are sandwiched by layers of [Ta(+5)3O13] triple octahedra. Additional Ta(+5) and Eu(+2) atoms provide the cohesion of these structural units. Twelve‐fold coordinated Eu(+2) atoms are situated on a triply degenerate position 33 pm displaced from the threefold axis of symmetry. A depletion of the Eu(+2) site from 6 to 5.5 atoms per unit cell reduces the number of electrons available for Ta‐Ta bonding from 15 to 14.67 electrons per cluster. Between 125 and 320 K Eu1.83Ta15O32 is semi‐conducting with a band gap of 0.23 eV. The course of the magnetization is consistently described with the Brillouin function in terms of a Mmol/(NAμB) versus B/T plot in the temperature range 5 K — 320 K and at magnetic flux densities 0.1 T — 5 T. At moderate flux densities (< 1 T) the magnetic moment agrees fairly well with the expected value of 7.94 μB for free Eu (2+) ions with 4f7 configuration in 8S7/2 ground state. Below 5 K, anisotropic magnetization measurements at flux densities B < 1 T point to an onset of an antiferromagnetic ordering of Eu spins within the layers and an incipient ferromagnetic ordering perpendicular to the layers. 相似文献
54.
We present a systematic procedure for the optimization of the expansion basis for the limited expansion of diatomic overlap density functional theory (LEDO-DFT) and report on optimized auxiliary orbitals for the Ahlrichs split valence plus polarization basis set (SVP) for the elements H, Li--F, and Na--Cl. A new method to deal with near-linear dependences in the LEDO expansion basis is introduced, which greatly reduces the computational effort of LEDO-DFT calculations. Numerical results for a test set of small molecules demonstrate the accuracy of electronic energies, structural parameters, dipole moments, and harmonic frequencies. For larger molecular systems the numerical errors introduced by the LEDO approximation can lead to an uncontrollable behavior of the self-consistent field (SCF) process. A projection technique suggested by L?wdin is presented in the framework of LEDO-DFT, which guarantees for SCF convergence. Numerical results on some critical test molecules suggest the general applicability of the auxiliary orbitals presented in combination with this projection technique. Timing results indicate that LEDO-DFT is competitive with conventional density fitting methods. 相似文献
55.
Peter Jutzi Andreas Klipp Andreas Mix Beate Neumann Hans-Georg Stammler 《Silicon Chemistry》2007,3(3-4):151-156
Reaction of pentamethylcyclopentadienyl(pentachloro)disilane (2), prepared from hexachlorodisilane and potassium pentamethylcyclopentadienide
(Cp*K), with a further equivalent of Cp*K leads selectively to the title compound Cp*
2
Si
2
Cl
4 (3) which was characterized by NMR and X-ray structural data. Dehalogenation of 3 with four equivalents of sodium naphthalenide
offers an alternative route for the synthesis of decamethylsilicocene (1).
Dedicated to Professor Mitsuo Kira on the occasion of being honoured with the Wacker Silicon Award 2005. 相似文献
56.
Wiegart L O'Flaherty SM Struth B 《Langmuir : the ACS journal of surfaces and colloids》2005,21(5):1695-1698
The influence of crystal surface charge on the thermodynamic and structural behavior of phospholipid monolayers has been investigated. We present how charged nanocrystals in the vicinity of an inherently nonordered lipid membrane provoke strong effects on the molecular arrangement within the monolayer. Apart from the induction of phase shifts and nucleation processes, the molecules were forced to adopt an ordered phase. A very recently developed X-ray scattering method is used for the first time to replace time-consuming specular reflectivity measurements. We conclude on the potential effects of crystal surface charge on cellular membranes. 相似文献
57.
The new term “Phanes” has been clearly defined and a nomenclature system tentatively developed. This system is comprehensible and of general application and at the same time relatively simple. The notations “nucleus”, “bridge”, “number of bridge members” and “number of ring members” are defined. In order to get a definite characterisation of the phanes which contain a carbocyclic nucleus, a carbocyclic and heterocyclic bridge the following terms: “carbophanes”, “carba-phanes” and “hetera-phanes” have been newly introduced. The prefix “hetera-” has been proposed as a general expression and as a representative term for the syllables “aza-”, “oxa-”, “thia-” and so on. The so called “a-nomenclature” is clearly called “hetera-nomenclature”. The new expressions “heteralogous” and “substitulogous” are explained. As the various examples will show, the “Phane-Nomenclature” can also be applied to the naming of complicated metallocenophanes. 相似文献
58.
Herbert Lindner Wilfried Helliger Bernd Puschendorf 《Journal of chromatography. A》1988,450(3):309-316
A procedure for the rapid separation of histones and high-mobility-group (HMG) proteins from Friend erythroleukaemic cells (line F4N) by reversed-phase high-performance liquid chromatography is reported. By using a Nucleosil 300-5 C4, column and a multistep water—acetonitrile gradient containing 0.1% trifluoroacetic acid, the HMG-1 and HMG-2 proteins, several his subtractions including H10, H4, H2B, two H2A variants and two H3 subtractions were separated. Under changed conditions, by applying a varied acetonitrile gradient system, even two H2B variants were fractionated. The methods described seem to be a real alternative to the time-consuming polyacrylamide gel electrophoresis. 相似文献
59.
Witte PT Chowdhury SR ten Elshof JE Sloboda-Rozner D Neumann R Alsters PL 《Chemical communications (Cambridge, England)》2005,(9):1206-1208
A "sandwich" type polyoxometalate catalyst ([MeN(n-C8H17)3]12[WZn3(ZnW9O34)2]) was very efficiently recycled by nanofiltration with almost quantitative retention, using an alpha-alumina supported mesoporous gamma-alumina membrane. 相似文献
60.
Bernd G. Müller 《Journal of fluorine chemistry》1982,20(3):291-299
Single crystals of CaPdF4 (purple) and CdPdF4 (dark blue) have been obtained by heating CaF2 (CdF2) with PdF2 at 820°C (900°C) for ca. 20–30 d in sealed Pd (Pt) tubes. CaPdF4 crystallizes tetragonal (KBrF4-Type) with a = 5.521, c = 10.570 Å (space group I4/mcm ? D184h, No. 140) Z = 4, 283 unique reflexions, R = 0.083; Rw = 0.079, CdPdF4 cubic (CaF2-variant) with a = 5.403 Å (space group Pa3 ? T6h, No. 205) Z = 4, 165 unique reflexions, R = 0.047, Rw = 0.032. The high pressure modification of PdF2, obtained by heating PdF2 in closed Pt-tubes under a pressure of ≈ 60 kbar and ‘HgPdF4’, both black, a = 5.327 Å and a = 5.43 Å are isotypic. CaPdF4 is diamagnetic, CdPdF4 and HPPdF2 are antiferromegnetic. 相似文献