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101.
Abstract Three novel bisphenols containing pendant ethynyl, hexynyl, and phenylethynyl groups were synthesized and used to prepare arylene ether polymers and copolymers. When heated to 250–350°C, the ethynyl groups react. After curing, the homopolymers were brittle due to the high crosslink density. Copolymers prepared using either 10 or 30 mol% of the ethynyl-containing bisphenol and either 90 or 70 mol% of the bisphenol with no ethynyl groups were relatively tough and formed creasible films. After a thermal cure, the copolymers became insoluble and exhibited high T gs and good thin film tensile properties. 相似文献
102.
Ditte C. Andersen Ida Skovrind Marlene Louise Christensen Charlotte H. Jensen Søren P. Sheikh 《Analytical and bioanalytical chemistry》2013,405(29):9585-9591
Stem cell therapy has opened up the possibility of treating numerous degenerating diseases. However, we are still merely at the stage of identifying appropriate sources of stem cells and exploring their full differentiation potential. Thus, tracking the stem cells upon in vivo engraftment and during in vitro co-culture is very important and is an area of research embracing many pitfalls. 5-Ethynyl-2′-deoxyuridine (EdU), a rather new thymidine analog incorporated into DNA, has recently been suggested to be a novel highly valid alternative to other dyes for labeling of stem cells and subsequent tracing of their proliferation and differentiation ability. However, our results herein do not at any stage support this recommendation, since EdU severely reduces the viability of stem cells. Accordingly, we found that transplanted EdU-labeled stem cells hardly survive upon in vivo transplantation into regenerating muscle, whereas stem cells labeled in parallel with another dye survived very well and also participated in myofiber formation. Similar data were obtained upon in vitro myogenic culture, and further analysis showed that EdU reduced cell numbers by up to 88 % and increased the cell volume of remaining cells by as much as 91 %. Even at low EdU concentrations, cell survival and phenotype were substantially compromised, and the myogenic differentiation potential was inhibited. Since we examined both primary derived cells and cell lines from several species with the same result, this appears to be a common trait of EdU. We therefore suggest that EdU labeling should be avoided (or used with precaution) for stem cell tracing purposes. Figure
Myoblasts were marked with DiI (red) and EdU (purple), and injected into lesioned skeletal muscle. At day 9 following transplantation, only DiI positive cells were observed and had participated in myofibre formation as (indicated by arrowheads) visualized by red fluorescence signals inside laminin (green) positive multinucleated myofibres. EdU was toxic to the engrafted cells, suggesting that this reagent is non-applicaple for tracing of stem cells. 相似文献
103.
Helene?Bonkerud?Dugstad Nickolaj?Jacob?PetersenEmail author Henrik?Jensen Charlotte?Gabel-Jensen Steen?Honoré?Hansen Stig?Pedersen-Bjergaard 《Analytical and bioanalytical chemistry》2014,406(2):421-429
A small and very simple electromembrane extraction probe (EME-probe) was developed and coupled directly to electrospray ionization mass spectrometry (ESI-MS), and this system was used to monitor in real time in vitro metabolism by rat liver microsomes of drug substances from a small reaction (incubation) chamber (37 °C). The drug-related substances were continuously extracted from the 1.0 mL metabolic reaction mixture and into the EME-probe by an electrical potential of 2.5 V. The extraction probe consisted of a 1-mm long and 350-μm ID thin supported liquid membrane (SLM) of 2-nitrophenyl octyl ether. The drugs and formed metabolites where extracted through the SLM and directly into a 3 μL min?1 flow of 60 mM HCOOH inside the probe serving as the acceptor solution. The acceptor solution was directed into the ESI-MS-system, and the MS continuously monitored the drug-related substances extracted by the EME-probe. The extraction efficiency of the EME-probe was dependant on the applied electrical potential and the length of the SLM, and these parameters as well as the volume of the reaction chamber were set to the values mentioned above to avoid serious depletion from the reaction chamber (soft extraction). Soft extraction was mandatory in order not to affect the reaction kinetics by sample composition changes induced by the EME-probe. The EME-probe/MS-system was used to establish kinetic profiles for the in vitro metabolism of promethazine, amitriptyline and imipramine as model substances. 相似文献
104.
Dr. Romaric Gérardy Dr. Anirudh M. K. Nambiar Travis Hart Prajwal T. Mahesh Prof. Dr. Klavs F. Jensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(43):e202201385
The implementation of self-optimizing flow reactors has been mostly limited to model reactions or known synthesis routes. In this work, a self-optimizing flow photochemistry platform is used to develop an original synthesis of the bioactive fragment of Salbutamol and derivatives. The key photochemical steps for the construction of the aryl vicinyl amino alcohol moiety consist of a C−C bond forming reaction followed by an unprecedented, high yielding (>80 %), benzylic oxidative cyclization. 相似文献
105.
Sheida Esmail Tehrani Long Quang Nguyen Giulia Garelli Bettina M. Jensen Tautgirdas Ruzgas Jenny Emnéus Stephan Sylvest Keller 《Electroanalysis》2021,33(12):2516-2528
A highly sensitive amperometric Prussian blue-based hydrogen peroxide sensor was developed using 3D pyrolytic carbon microelectrodes. A 3D printed multielectrode electrochemical cell enabled simultaneous highly reproducible Prussian blue modification on multiple carbon electrodes. The effect of oxygen plasma pre-treatment and deposition time on Prussian blue electrodeposition was studied. The amperometric response of 2D and 3D sensors to the addition of hydrogen peroxide in μM and sub-μM concentrations in phosphate buffer was investigated. A high sensitivity comparable to flow injection systems and a detection limit of 0.16 μM was demonstrated with 3D pyrolytic carbon microelectrodes at stirred batch condition 相似文献
106.
Kanyal Supriya S. Jensen David S. Dadson Andrew E. Vanfleet Richard R. Davis Robert C. Linford Matthew R. 《平面色谱法杂志一现代薄层色谱法》2014,27(3):151-156
JPC – Journal of Planar Chromatography – Modern TLC - We describe the direct, conformal, atomic layer deposition (ALD) of silica onto carbon nanotubes (CNTs) in the microfabrication of... 相似文献
107.
Casper Jon Steenbjerg Ibsen Bjørn Fridur Mikladal Uffe Bjørnholt Jensen Assoc. Prof. Henrik Birkedal 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(49):16112-16120
Three dimensional hierarchical materials are widespread in nature but are difficult to synthesize by using self‐assembly/organization. Here, we employ a gel–liquid interface to obtain centimeter‐long ~100 μm diameter tubes with complex mineral wall structures that grow from the interface into solution. The gel, made from gelatin, is loaded with metal chloride salt, whereas the solution is a high pH anion source. Tubes were obtained with a range of cations (Ca2+, Sr2+, Ba2+, Cu2+, and Zn2+) and anions (CO32? and PO43?). The crystalline phases found in the tube walls corresponded to expectations from solution chemistries and phase solubilities. The growth mechanism is found to be akin to that of chemical gardens. The divalent cations modify the strength of the gelatin gel in a manner that involves not only simple electrostatic screening, but also ion‐specific effects. Thus, tubes were not obtained for those ions and/or concentrations that significantly changed the gel’s mechanical structure. At high Cu2+ loading, for example, vertical convection bands, not Liesegang bands, were observed in the gels. 相似文献
108.
Monitoring the Transition from Spherical to Polymer‐like Surfactant Micelles Using Small‐Angle X‐Ray Scattering
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Dr. Grethe Vestergaard Jensen Dr. Reidar Lund Dr. Jérémie Gummel Dr. Theyencheri Narayanan Prof. Jan Skov Pedersen 《Angewandte Chemie (International ed. in English)》2014,53(43):11524-11528
Despite over a century of modern surfactant science, the kinetic pathways of morphological transitions in micellar systems are still not well understood. This is mainly as a result of the lack of sufficiently fast methods that can capture the structural changes of such transitions. Herein, a simple surfactant system consisting of sodium dodecyl sulfate (SDS) in aqueous NaCl solutions is investigated. Combining synchrotron radiation small‐angle X‐ray scattering (SAXS) with fast stopped‐flow mixing schemes allows monitoring the process where polymer‐like micelles are formed from globular micelles when the salt concentration is suddenly increased. The results show that “worm‐like” micelles are formed by fusion of globular micelles and short cylinders in a fashion that bears similarities to a step‐like polymerization process. 相似文献
109.
Hendrik F. Hameka Silvio L. Emery George R. Famini James O. Jensen Joseph M. Leonard Dennis J. Reutter 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-4):373-388
Abstract We report the computed equilibrium geometries and vibrational infrared frequencies of a group of thirteen mercaptans and sulfides. The computations were based on the Gaussian 86 Program Package utilizing 3-21G basis sets. The theoretical bond distances and bond angles are in agreement with the available experimental data. The agreement between computed frequencies and available experimental values seems reasonable. We also used the computations as guidelines for the assignment of available experimental infrared frequencies. We believe that it is possible to make reliable frequency predictions by combining computations with available experimental data for groups of similar molecules. However, it is necessary to introduce different correction factors for different types of vibrational modes if we use 3-21G basis sets. 相似文献
110.
K E Jensen T Grube C Thomsen P G S?rensen P Christoffersen H Karle O Henriksen 《Magnetic resonance imaging》1988,6(3):291-292
In vitro as well as in vivo studies have shown prolonged T1 relaxation times in patients with acute leukemia. The mechanism behind this finding is not known. In order to evaluate if this was specific for leukemia we examined eight patients with polycythemia vera, representing a condition with a rather benign bone marrow neoplasia. In this group of patients we found prolonged T1 relaxation times but normal T2 relaxation times. This may indicate that the prolonged T1 relaxation time seen in leukemic bone marrow is not due to the malignant cell per se. 相似文献