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931.
A far-red emitting probe for unambiguous detection of mobile zinc in acidic vesicles and deep tissue
Pablo Rivera-Fuentes Alexandra T. Wrobel Melissa L. Zastrow Mustafa Khan John Georgiou Thomas T. Luyben John C. Roder Kenichi Okamoto Stephen J. Lippard 《Chemical science》2015,6(3):1944-1948
Imaging mobile zinc in acidic environments remains challenging because most small-molecule optical probes display pH-dependent fluorescence. Here we report a reaction-based sensor that detects mobile zinc unambiguously at low pH. The sensor responds reversibly and with a large dynamic range to exogenously applied Zn2+ in lysosomes of HeLa cells, endogenous Zn2+ in insulin granules of MIN6 cells, and zinc-rich mossy fiber boutons in hippocampal tissue from mice. This long-wavelength probe is compatible with the green-fluorescent protein, enabling multicolor imaging, and facilitates visualization of mossy fiber boutons at depths of >100 μm, as demonstrated by studies in live tissue employing two-photon microscopy. 相似文献
932.
International Intercomparison of Solar UVR Spectral Measurement Systems in Melbourne in 2013
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Peter Gies Rebecca Hooke Richard McKenzie John O'Hagan Stuart Henderson Andy Pearson Marina Khazova John Javorniczky Kerryn King Matt Tully Michael Kotkamp Bruce Forgan Stephen Rhodes 《Photochemistry and photobiology》2015,91(5):1237-1246
Monitoring ambient solar UVR levels provides information on how much there is in both real time and historically. Quality assurance of ambient measurements of solar UVR is critical to ensuring accuracy and stability and this can be achieved by regular intercomparisons of spectral measurement systems with those of other organizations. In October and November of 2013 a solar UVR spectroradiometer from Public Health England (PHE) was brought to Melbourne for a campaign of intercomparisons with a new Bentham spectrometer of Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) and one at the Australian Bureau of Meteorology (BOM), supported by New Zealand's National Institute for Water and Atmosphere (NIWA). Given all three spectroradiometers have calibrations that are traceable to various national standards, the intercomparison provides a chance to determine measurement uncertainties and traceability that support UV measurement networks in Australia, New Zealand and the UK. UV Index measurements from all three systems were compared and ratios determined for clear sky conditions when the scans from each instrument were within 2 min of each other. While wavelengths below 305 nm showed substantial differences between the PHE unit and the two other systems, overall the intercomparison results were encouraging, with mean differences in measured UV Index between the BOM/NIWA and those of PHE and ARPANSA of <0.1% and 7.5%, respectively. 相似文献
933.
Stephen P. Cooper Kevin I. Booker‐Milburn 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(22):6596-6600
Polyheterocycles are found in many natural products and are useful moieties in functional materials and drug design. As part of a program towards the synthesis of Stemona alkaloids, a novel palladium(II)‐catalyzed C H activation strategy for the construction of such systems has been developed. Starting from simple 1,3‐dienyl‐substituted heterocycles, a large range of polycyclic systems containing pyrrole, indole, furan and thiophene moieties can be synthesized in a single step. 相似文献
934.
Ting‐Zheng Xie Kai Guo Zaihong Guo Wen‐Yang Gao Lukasz Wojtas Guo‐Hong Ning Mingjun Huang Xiaocun Lu Jing‐Yi Li Sheng‐Yun Liao Yu‐Sheng Chen Charles N. Moorefield Mary Jane Saunders Stephen Z. D. Cheng Chrys Wesdemiotis George R. Newkome 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2015,127(32):9259-9259
935.
Wei-Chang Tseng Keng-Chang Hsu Christopher Stephen Shiea Yeou-Lih Huang 《Analytica chimica acta》2015
Trace element speciation in biomedical and environmental science has gained increasing attention over the past decade as researchers have begun to realize its importance in toxicological studies. Several nanomaterials, including titanium dioxide nanoparticles (nano-TiO2), carbon nanotubes (CNTs), and magnetic nanoparticles (MNPs), have been used as sorbents to separate and preconcentrate trace element species prior to detection through mass spectrometry or optical spectroscopy. Recently, these nanomaterial-based speciation techniques have been integrated with microfluidics to minimize sample and reagent consumption and simplify analyses. This review provides a critical look into the present state and recent applications of nanomaterial-based microanalytical systems in the speciation of trace elements. The adsorption and preconcentration efficiencies, sample volume requirements, and detection limits of these nanomaterial-based speciation techniques are detailed, and their applications in environmental and biological analyses are discussed. Current perspectives and future trends into the increasing use of nanomaterial-based microfluidic techniques for trace element speciation are highlighted. 相似文献
936.
Mechanistic Insights into the Post‐Cyclization Isomerization in Gold‐Catalyzed 7‐exo‐dig‐Hydroarylations
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M. Sc. Daniel Pflästerer Sören Schumacher Dr. Matthias Rudolph Prof. Dr. A. Stephen K. Hashmi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(32):11585-11589
The subsequent double‐bond isomerization in the synthesis of dibenzocycloheptenes and their heteroaromatic analogues was investigated. In the case of biphenyls, a basic additive completely prevented an isomerization to the thermodynamic product. With electron‐rich intramolecular heteroaromatic nucleophiles, the isomerization was still observed, but the kinetic product can be obtained by careful control of the reaction times in most cases. Mechanistic studies demonstrated that a slow isomerization is also possible with the gold catalyst at elevated temperatures, but much faster isomerization rates were observed with acidic additives. An observed initiation period for the gold‐catalyzed isomerization indicates that not the homogenous catalyst, but a decomposition product of it may be the catalytically active species. 相似文献
937.
Enhanced Photocatalytic Reduction of CO2 to CO through TiO2 Passivation of InP in Ionic Liquids
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Guangtong Zeng Jing Qiu Bingya Hou Haotian Shi Dr. Yongjing Lin Mark Hettick Prof. Ali Javey Prof. Stephen B. Cronin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(39):13502-13507
A robust and reliable method for improving the photocatalytic performance of InP, which is one of the best known materials for solar photoconversion (i.e., solar cells). In this article, we report substantial improvements (up to 18×) in the photocatalytic yields for CO2 reduction to CO through the surface passivation of InP with TiO2 deposited by atomic layer deposition (ALD). Here, the main mechanisms of enhancement are the introduction of catalytically active sites and the formation of a pn‐junction. Photoelectrochemical reactions were carried out in a nonaqueous solution consisting of ionic liquid, 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([EMIM]BF4), dissolved in acetonitrile, which enables CO2 reduction with a Faradaic efficiency of 99 % at an underpotential of +0.78 V. While the photocatalytic yield increases with the addition of the TiO2 layer, a corresponding drop in the photoluminescence intensity indicates the presence of catalytically active sites, which cause an increase in the electron‐hole pair recombination rate. NMR spectra show that the [EMIM]+ ions in solution form an intermediate complex with CO2?, thus lowering the energy barrier of this reaction. 相似文献
938.
Total Synthesis of cis‐Clavicipitic Acid from Asparagine via Ir‐Catalyzed CH bond Activation as a Key Step
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Yu‐ki Tahara Mamoru Ito Dr. Kyalo Stephen Kanyiva Prof. Dr. Takanori Shibata 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(32):11340-11343
4‐Substituted tryptophan derivatives and the total synthesis of cis‐clavicipitic acid were achieved in reactions in which Ir‐catalyzed C?H bond activation was a key step. The starting material for these reactions is asparagine, which is a cheap natural amino acid. The reductive amination step from the 4‐substituted tryptophan derivative gave cis‐clavicipitic acid with perfect diastereoselectivity. 相似文献
939.
Dr. Igor V. Pimkov Dr. Barbara Serli‐Mitasev Antoinette A. Peterson Stephen C. Ratvasky Dr. Bernd Hammann Prof. Partha Basu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(47):17057-17072
Molybdopterin is an essential cofactor for all forms of life. The cofactor is composed of a pterin moiety appended to a dithiolene‐functionalized pyran ring, and through the dithiolene moiety it binds metal ions. Different synthetic strategies for dithiolene‐functionalized pyran precursors that have been designed and synthesized are discussed. These precursors also harbor 1,2‐diketone or osone functionality that has been condensed with 1,2‐diaminobenzene or other heterocycles resulting in several quinoxaline or pterin derivatives. Use of additives improves the regioselectivity of the complexes. The molecules have been characterized by 1H and 13C NMR and IR spectroscopies, as well as by mass spectrometry. In addition, several compounds have been crystallographically characterized. The geometries of the synthesized molecules are more planar than the geometry of the cofactor found in proteins. 相似文献
940.