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排序方式: 共有568条查询结果,搜索用时 31 毫秒
561.
Smith DF Schaub TM Rodgers RP Hendrickson CL Marshall AG 《Analytical chemistry》2008,80(19):7379-7382
We describe automation of liquid injection field desorption/ionization (LIFDI) for reproducible sample application, improved spectral quality, and high-throughput analyses. A commercial autosampler provides reproducible and unattended sample application. A custom-built field desorption (FD) controller allows data station or front panel control of source parameters including high-voltage limit/ramp rate, emitter heating current limit/ramp rate, and feedback control of emitter heating current based on ion current measurement. Automated LIFDI facilitates ensemble averaging of hundreds of Fourier transform ion cyclotron resonance mass spectra for increased dynamic range, mass accuracy, and S/N ratio relative to single-application FD experiments, as shown here for a South American crude oil. This configuration can be adapted to any mass spectrometer with an LIFDI probe. 相似文献
562.
Luszik-Bhadra M Bartlett D Boschung M Coeck M Curzio G Derdau D d'Errico F Fiechtner A Itié C Kyllönen JE Lacoste V Lahaye T Lindborg L Molinos C Reginatto M Schuhmacher H Tanner R Vanhavere F 《Radiation protection dosimetry》2006,120(1-4):378-382
This work describes spectral distributions of neutrons obtained as function of energy and direction at four workplace fields at the Krümmel reactor in Germany. Values of personal dose equivalent H(p)(10) and effective dose E are determined for different directions of a person's orientation in these fields and readings of personal neutron dosemeters--especially electronic dosemeters--are discussed with respect to H(p)(10) and E. 相似文献
563.
Mabuza Mzwandile Annandale John Steyn Martin Tanner Phil 《Mine Water and the Environment》2023,42(1):98-110
Mine Water and the Environment - Untreated acid mine drainage (AMD) is being considered for crop irrigation on strategically limed soils, but foliar scorching is of potential concern. To test... 相似文献
564.
Kwing Yeung Chan Andrew Brian Kinghorn Marcel Hollenstein Julian Alexander Tanner 《Chembiochem : a European journal of chemical biology》2022,23(15):e202200006
In the past three decades, in vitro systematic evolution of ligands by exponential enrichment (SELEX) has yielded many aptamers for translational applications in both research and clinical settings. Despite their promise as an alternative to antibodies, the low success rate of SELEX (∼30 %) has been a major bottleneck that hampers the further development of aptamers. One hurdle is the lack of chemical diversity in nucleic acids. To address this, the aptamer chemical repertoire has been extended by introducing exotic chemical groups, which provide novel binding functionalities. This review will focus on how modified aptamers can be selected and evolved, with illustration of some successful examples. In particular, unique chemistries are exemplified. Various strategies of incorporating modified building blocks into the standard SELEX protocol are highlighted, with a comparison of the differences between pre-SELEX and post-SELEX modifications. Nucleic acid aptamers with extended functionality evolved from non-natural chemistries will open up new vistas for function and application of nucleic acids. 相似文献
565.
Jenna A. Tan Jordan T. Dull Steven E. Zeltmann Jakhangirkhodja A. Tulyagankhodjaev Holly M. Johnson Alex Liebman-Peláez Brendan D. Folie Sven A. Dönges Omar Khatib Jonathan G. Raybin Trevor D. Roberts Leo M. Hamerlynck Christian P. N. Tanner Jina Lee Colin Ophus Karen C. Bustillo Markus B. Raschke Hendrik Ohldag Andrew M. Minor Barry P. Rand Naomi S. Ginsberg 《Advanced functional materials》2023,33(13):2207867
Multimodal multiscale characterization provide opportunities to study organic semiconducting thin films with multiple length scales, across multiple platforms, to elucidate crystallization mechanisms of the various microstructures that impact functionality. With polarized scanning transmission X-ray and 4D-scanning transmission electron microscopy, hybrid crystalline structures in rubrene thin films in which large crystalline domains surround a common nucleus and transition to a spherulite morphology at larger radii is observed. These high-resolution techniques reveal how azimuthal orientational discontinuities at smaller radii are erased as spherulite morphology takes hold. In situ crystallization in the films with optical microscopy is also captured, discovering the importance of considering the initial temperature increase of a film during thermal annealing over the crystallization timescale. This kinetic information of the radial crystallization rate and of corresponding film heating kinetics is used to estimate the temperature at which the larger crystalline regions transition into a spherulite. By combining the results obtained from the different characterization modes, it is learned that thermal conditions can sensitively affect the crystallization of rubrene and other organic thin films. The observations suggest opportunities for more complex temperature-dependent processing to maximize hybrid structures’ functionality in organic thin films and demonstrate that multimodal studies deepen the understanding of structure-function dynamics. 相似文献
566.
Dmytro Voskoboinyk Niusha Mahmoodi Chang Sheng-Huei Lin Michael E. P. Murphy Martin E. Tanner 《Chembiochem : a European journal of chemical biology》2023,24(11):e202300205
The O-acetylation of the muramic acid residues in peptidoglycan (PG) is a modification that protects the bacteria from lysis due to the action of lysozyme. In Gram-negative bacteria, deacetylation is required to allow lytic transglycosylases to promote PG cleavage during cell growth and division. This deacetylation is catalyzed by O-acetylpeptidoglycan esterase (Ape) which is a serine esterase and employs covalent catalysis via a serine-linked acyl enzyme intermediate. Loss of Ape activity affects the size and shape of bacteria and dramatically reduces virulence. In this work, we report the first rationally designed aldehyde-based inhibitors of Ape from Campylobacter jejuni. The most potent of these acts as a competitive inhibitor with a Ki value of 13 μM. We suspect that the inhibitors are forming adducts with the active site serine that closely mimic the tetrahedral intermediate of the normal catalytic cycle. Support for this notion is found in the observation that reduction of the aldehyde to an alcohol effectively abolishes the inhibition. 相似文献
567.
Robin Kerr Thomas J. Macdonald Alex J. Tanner Jiangdong Yu Julia A. Davies Helen H. Fielding Geoff Thornton 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(40):2301014
Hybrid organic–inorganic perovskites (HOIPs) have shown great promise in a wide range of optoelectronic applications. However, this performance is inhibited by the sensitivity of HOIPs to various environmental factors, particularly high levels of relative humidity. This study uses X-ray photoelectron spectroscopy (XPS) to determine that there is essentially no threshold to water adsorption on the in situ cleaved MAPbBr3(001) single crystal surface. Using scanning tunneling microscopy (STM), it shows that the initial surface restructuring upon exposure to water vapor occurs in isolated regions, which grow in area with increasing exposure, providing insight into the initial degradation mechanism of HOIPs. The electronic structure evolution of the surface was also monitored via ultraviolet photoemission spectroscopy (UPS), evidencing an increased bandgap state density following water vapor exposure, which is attributed to surface defect formation due to lattice swelling. This study will help to inform the surface engineering and designs of future perovskite-based optoelectronic devices. 相似文献
568.
Tanner G. Hoog Matthew R. Pawlak Lauren M. Aufdembrink Benjamin R. Bachan Matthew B. Galles Nicholas B. Bense Katarzyna P. Adamala Aaron E. Engelhart 《Chembiochem : a European journal of chemical biology》2022,23(9):e202200090
Here we demonstrate a switchable DNA electron-transfer catalyst, enabled by selective destabilization of secondary structure by the denaturant, perchlorate. The system is comprised of two strands, one of which can be selectively switched between a G-quadruplex and duplex or single-stranded conformations. In the G-quadruplex state, it binds hemin, enabling peroxidase activity. This switching ability arises from our finding that perchlorate, a chaotropic Hofmeister ion, selectively destabilizes duplex over G-quadruplex DNA. By varying perchlorate concentration, we show that the DNA structure can be switched between states that do and do not catalyze electron-transfer catalysis. State switching can be achieved in three ways: thermally, by dilution, or by concentration. 相似文献