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181.
Agnès Hagege Christina Troyer Manfred Grasserbauer Maurice J. F. Leroy 《Mikrochimica acta》1997,127(1-2):113-118
The behaviour of four biologically relevant selenium compounds (Se(VI), Se(IV), selenomethionine and selenocystine) in capillary zone electrophoresis (CZE) was investigated. Parameters which affect the separation, detection and sample introduction were investigated to improve the sensitivity of the analysis. Short-term repeatability was evaluated and detection limits were found to be in the g·l–1 range. 相似文献
182.
In a quest to develop an effective, scalable synthesis of (+)-spongistatin 1 ( 1), we devised a concise, third-generation scalable synthesis of (+)- 7, the requisite F-ring tetrahydropyran aldehyde, employing a proline-catalyzed cross-aldol reaction. Subsequent elaboration to (+)-EF Wittig salt (+)- 3, followed by union with advanced ABCD aldehyde (-)- 4, macrolactonization and global deprotection permitted access to >1.0 g of totally synthetic (+)-spongistatin 1 ( 1). 相似文献
183.
Molecular dynamics simulations were performed to study the translocation of single-stranded (ss) DNA through the nanoscale gap between the nanoscale electrodes of a proposed genomic sequencing device. An applied electric field forces the ssDNA to move in the direction of the nanoscale gap in platinum electrodes. A series of simulations utilizing eight different nanoscale gap distances as well as seven different nucleotide chain lengths were performed to determine the impact of these variables on the overall design of the sequencing device and the translocation behavior of ssDNA. The results clearly indicate a threshold value of the gap width below which the ssDNA will readily enter and traverse the nanoscale gap. Translocation velocities obtained for various chain lengths were consistent with simulated bulk data; however, successful translocation was inconsistent, possibly related to the sample's affinity for the metal electrodes. An attempt at overcoming this barrier was made through the implementation of shaped electrodes as well as pre-threading of the ssDNA sample. 相似文献
184.
Roos PH Venkatachalam A Manz A Waentig L Koehler CU Jakubowski N 《Analytical and bioanalytical chemistry》2008,392(6):1135-1147
Numerous structurally and enzymatically similar cytochromes P450 (CYPs) are involved in the metabolism of xenobiotics and
are present in different amounts and with different enzyme profiles in human tissues and cells. Analysis of their adaptively
regulated and individually variable patterns is a peculiar analytical challenge. We developed a laser ablation inductively
coupled plasma mass spectrometry (LA-ICP-MS) based method for concomitant detection and semiquantitative determination of
electrophoretically separated and blotted CYPs. The first results are given here for the two enzymes CYP1A1 and CYP2E1. Specific
monoclonal antibodies directed against the enzymes were differentially labelled with europium via a covalently linked chelator
and with iodine, respectively. Analysis of the modified antibodies shows that both europium and iodine are coupled to the
heavy and the light chains of the antibodies. Also, the antibodies maintained their antigen-binding properties after labelling
as demonstrated by LA-ICP-MS-analysed immunoblots. The method allowed us to detect specifically and concomitantly both CYP
enzymes in complex biological samples, i.e. microsomes of rat liver and minipig duodenum, which are characterized by different
levels and proportions of the two CYP enzymes. A strong CYP1A1 signal is found in liver microsomes of 3-methylcholanthrene-treated
rats, while it is (nearly) absent in liver microsomes of rats treated with isonocotinic acid hydrazide (isoniazid). The constitutively
expressed CYP2E1 is found in microsomes of both treatment groups. Duodenal microsomes of minipigs orally exposed to polycyclic
aromatic hydrocarbons show a clear CYP1A1 signal. Low levels of CYP2E1 can also be detected in these microsomes. The LA-ICP-MS
method allows concomitant determination of CYPs, thereby exhibiting sensitivity similar to that of conventional chemoluminescence
detection via peroxidase-labelled secondary antibodies. The latter method allows readout of a single CYP protein in a 1D separation.
Although the results presented here are only for labelling by use of the elements iodine and europium, the same strategy can
be applied also for other lanthanide elements in combination with chelating compounds, so LA-ICP-MS of western blots offers
a new capability to be applied for highly multiplexed CYP determinations via labelled antibodies. 相似文献
185.
Kontoyianni C Sideratou Z Theodossiou T Tziveleka LA Tsiourvas D Paleos CM 《Macromolecular bioscience》2008,8(9):871-881
A hyperbranched aliphatic polyester has been functionalized with PEG chains to afford a novel water-soluble BH40-PEG polymer which exhibits unimolecular micellar properties, and is therefore appropriate for application as a drug-delivery system. The solubility of the anticancer drug paclitaxel was enhanced by a factor of 35, 110, 230, and 355 in aqueous solutions of BH40-PEG of 10, 30, 60, and 90 mg x mL(-1), respectively. More than 50% of the drug is released at a steady rate and release is almost complete within 10 h. The toxicity of BH40-PEG was assessed in vitro with A549 human lung carcinoma cells and found to be nontoxic for 3 h incubation up to a 1.75 mg x mL(-1) concentration while LD50 was 3.5 mg x mL(-1). Finally, it was efficiently internalized in cells, primarily in the absence of foetal bovine serum, while confocal microscopy revealed the preferential localization of the compound in cell nuclei. [Figure: see text]. 相似文献
186.
187.
Oliver Staller Christina Mitterbauer Katharina Mayr 《Central European Journal of Chemistry》2008,6(4):535-541
In this paper we report a method to determine tensile strengths and Young’s modulus of cubic biaxial textured metal tapes
used as substrate materials for coated conductors (CC). Simplicity, rapidity and reproducibility of the procedure are important
for the evaluation of continuous in-house productions. Our approach is based on the EN 10002-1 B tensile test method. A key
role for satisfactory results is the sample preparation of 100–250 μm thick tapes, which will be described in detail. Copper
(E-Cu57) can be successfully transformed to cubic biaxial textured substrates. Best results were achieved by annealing between
750°C and 850°C in reducing atmosphere. Best FWHM values for the ψ scan are 5.51° and for the ϕ scan are 4.5°. Pole figure
analysis verified the sharp {001} <100> texture of the tape. Vickers hardness measurements (HV 0.1) for the cold worked material
yielded values of 135 and for the annealed tape, values of 37. The ultimate tensile yield strength Rm of the textured substrate
is 150 MPa and thus significantly lower than that for the cold worked material (413 MPa). Cubic biaxial substrates could be
manufactured from Isotan CuNi44 (WM49) bars. Best results were achieved by annealing at 1200°C in reducing atmosphere. Pole
figure analysis verified the {001} <100> texture with other low intensity texture components. Vickers hardness measurements
(HV 0.1) for the cold worked material yielded values of 236 and for the annealed tape values of 92. The ultimate tensile yield
strength R
m of the textured substrate is 300 MPa and thus significantly lower than that for the cold worked material (723 MPa).
相似文献
188.
Christina Conroy 《Acta Analytica》2008,23(4):367-372
In his “Space, supervenience and substantivalism”, Le Poidevin proposes a substantivalism in which space is discrete, implying
that there are unmediated spatial relations between neighboring primitive points. This proposition is motivated by his concern
that relationism suffers from an explanatory lacuna and that substantivalism gives rise to a vicious regress. Le Poidevin
implicitly requires that the relationist be committed to the “only x and y” principle regarding spatial relations. It is not obvious that the relationist is committed to this principle in such a context.
An additional motivation for Le Poidevin's argument, that space should be considered to be discrete, is that he believes that
substantivalists are committed to a vicious regress. I show that the regress is in fact not of the vicious variety. These
two main arguments show that Le Poidevin's suggestion that we drop the density postulate for space is unnecessary.
相似文献
Christina ConroyEmail: |
189.
Dimitrova A Taseva C Yordanov ND 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,70(5):953-957
The paper is a study on the formation and properties of mixed-chelate copper(II) complexes, in which one ligand is strongly covalently bound diselenocarbamate (dsc), and the other belongs to a series of differently substituted acetylacetonates (acac), all forming weak covalent bonds. Thenoyltrifluoro- and trifluoro- substituted acetylacetonates only partly form mixed-chelate complexes, stable in toluene, benzene or dichloromethane, but gradually decomposing in chloroform or carbontetrachloride by analogy with Cu(Et(2)dsc)(2) behavior in these solvents. Hexafluoro-acetylacetonato copper(II) completely turns into a mixed-chelate Cu(dsc)(hfacac), which remains unchanged for more than 8 months of monitoring in all solvents used. The stability of Cu(dsc)(hfacac) is attributed to the reduced remaining negative charge on selenium atom embarrassing the formation of weak D-A complex with haloalkanes. The obtained EPR parameters suggest significant lowering of the contribution of the 4s AO of copper(II) in the mixed-chelate complexes. It is shown that Cu(acac)(2) does not react with Cu(Et(2)dsc)(2). 相似文献
190.