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41.
Damien Weidmann Chad B. Roller Clive Oppenheimer Alan Fried Frank K. Tittel 《Isotopes in environmental and health studies》2013,49(4):293-302
Recent developments of two mid-infrared tunable laser spectrometers dedicated to carbon isotope ratio determination are presented. First, a field deployable quantum cascade laser-based sensor is described, along with line selection strategy for 13/12CO2 ratio measurements. Secondly, an instrument architecture based on difference frequency generation is presented. The analyses of fundamental limitations, specifically temperature and pressure stability, and water vapor collision broadening, are detailed. 相似文献
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Starodubtseva MN Tattersall AL Kuznetsova TG Yegorenkov NI Ellory JC 《Bioelectrochemistry (Amsterdam, Netherlands)》2008,73(2):155-162
The changes in passive ion permeability of the red blood cell membrane after peroxynitrite action (3 microM-3 mM) have been studied by biophysical (using radioisotopes of rubidium, sodium and sulphur (sulphate)) and electrophysiological methods. The enhancement of passive membrane permeability to cations (potassium and sodium ions) and the inhibition of anion flux through the anion exchanger in peroxynitrite-treated red blood cells were revealed. In patch-clamp experiments the whole-cell conductance after peroxynitrite (80 muM) treatment of red blood cells increased 3-3.5-fold with a shift in the reversal potential from -7.0+/-1.5 mV to -4.3+/-0.9 mV (n=7, p=0.005). The addition of cobalt and nickel ions to red blood cell suspensions before peroxynitrite treatment had no effect on the peroxynitrite-induced cation flux but zinc ions in the same condition decreased cation flux about 2-fold. Using atomic force microscopy methods we revealed an increase in red blood cell membrane stiffness and the membrane skeleton complexity after peroxynitrite action. We conclude that the peroxynitrite-induced water and ion imbalance and reorganization in membrane structure lead to crenation of red blood cells. 相似文献
46.
The gene expression of human embryonic stem cells (hESC) is a critical aspect for understanding the normal and pathological development of human cells and tissues. Current bulk gene expression assays rely on RNA extracted from cell and tissue samples with various degree of cellular heterogeneity. These 'cell population averaging' data are difficult to interpret, especially for the purpose of understanding the regulatory relationship of genes in the earliest phases of development and differentiation of individual cells. Here, we report a microfluidic approach that can extract total mRNA from individual single-cells and synthesize cDNA on the same device with high mRNA-to-cDNA efficiency. This feature makes large-scale single-cell gene expression profiling possible. Using this microfluidic device, we measured the absolute numbers of mRNA molecules of three genes (B2M, Nodal and Fzd4) in a single hESC. Our results indicate that gene expression data measured from cDNA of a cell population is not a good representation of the expression levels in individual single cells. Within the G0/G1 phase pluripotent hESC population, some individual cells did not express all of the 3 interrogated genes in detectable levels. Consequently, the relative expression levels, which are broadly used in gene expression studies, are very different between measurements from population cDNA and single-cell cDNA. The results underscore the importance of discrete single-cell analysis, and the advantages of a microfluidic approach in stem cell gene expression studies. 相似文献
47.
S. M. Whitney R. G. Downing S. Biegalski D. S. O’Kelly 《Journal of Radioanalytical and Nuclear Chemistry》2008,276(1):257-261
The University of Texas (UT) at Austin has collaborated with the National Institute of Standards and Technology for comparisons
of concentration versus depth profiles of samples containing 10B. Technology sharing from NIST has allowed UT to avoid many initial set backs such that significant advancements in the UT-NDP
facility’s experimental and analytical methodology have been achieved. UT has analyzed two samples loaned to them from NIST.
The collaborative effort between the two institutions has given the UT-NDP facility the proper tools to begin profiling more
advanced samples in hopes of meeting the capabilities set by NIST in the NDP field. The UT-NDP facility was able to profile
a borosilicate surface deposit onto silicon such that the concentrations of 10B at various depths of the deposit were determined and fit well to a Pearson distribution. 相似文献
48.
Andreas A. Danopoulos Pamela Cole Steven P. Downing David Pugh 《Journal of organometallic chemistry》2008,693(21-22):3369-3374
The new imidazolium salts functionalised with the trimethylsilyl ester group 1a–c, were easily obtained by quaternisation of alkyl- or aryl-imidazoles with trimethylsilyl bromoacetate. Salt 1a was isolated and fully characterised. It reacted with mesityl copper (Cu5Mes5) under trimethylsilyl abstraction to form the complex 2. Methanolysis of 1a–c gave good yields of the carboxylic acid functionalised imidazolium salts 3a–c. Deprotonation of the latter in liquid ammonia led to the zwitterionic imidazolium carboxylates 4a–c. Reaction of 4a with (Cu5Mes5) gave solutions from which the insoluble polymeric 5a crystallised slowly. Generation of the carboxylate-functionalised NHC in situ followed by reaction with Pd(OOCCH3)2 gave the new complex 6a in which the NHC-carboxylate ligand is chelate bidentate. 相似文献
49.
Britcher L Barnes TJ Griesser HJ Prestidge CA 《Langmuir : the ACS journal of surfaces and colloids》2008,24(15):7625-7627
Porous silicon has received considerable interest in recent years in a range of biomedical applications, with its performance determined by surface chemistry. In this work, we investigate the PEGylation of porous silicon wafers using click chemistry. The porous silicon wafer surface chemistry was monitored at each stage of the reaction via photoacoustic Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, whereas sessile drop contact angle and model protein adsorption measurements were used to characterize the final PEGylated surface. This work highlights the simplicity of click-chemistry-based functionalization in tailoring the porous silicon surface chemistry and controlling protein-porous silicon interactions. 相似文献
50.
Cyclometalated Palladium(II) N‐Heterocyclic Carbene Complexes: Anticancer Agents for Potent In Vitro Cytotoxicity and In Vivo Tumor Growth Suppression
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Dr. Tommy Tsz‐Him Fong Dr. Chun‐Nam Lok Dr. Clive Yik‐Sham Chung Dr. Yi‐Man Eva Fung Dr. Pui‐Keong Chow Pui‐Ki Wan Prof. Dr. Chi‐Ming Che 《Angewandte Chemie (International ed. in English)》2016,55(39):11935-11939
Palladium(II) complexes are generally reactive toward substitution/reduction, and their biological applications are seldom explored. A new series of palladium(II) N‐heterocyclic carbene (NHC) complexes that are stable in the presence of biological thiols are reported. A representative complex, [Pd(C^N^N)(N,N′‐nBu2NHC)](CF3SO3) ( Pd1 d , HC^N^N=6‐phenyl‐2,2′‐bipyridine, N,N′‐nBu2NHC=N,N′‐di‐n‐butylimidazolylidene), displays potent killing activity toward cancer cell lines (IC50=0.09–0.5 μm ) but is less cytotoxic toward a normal human fibroblast cell line (CCD‐19Lu, IC50=11.8 μm ). In vivo anticancer studies revealed that Pd1 d significantly inhibited tumor growth in a nude mice model. Proteomics data and in vitro biochemical assays reveal that Pd1 d exerts anticancer effects, including inhibition of an epidermal growth factor receptor pathway, induction of mitochondrial dysfunction, and antiangiogenic activity to endothelial cells. 相似文献