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81.
Peter Roselt Carleen Cullinane Wayne Noonan Hassan Elsaidi Peter Eu Leonard I. Wiebe 《Molecules (Basel, Switzerland)》2020,25(23)
Vitamin E, a natural antioxidant, is of interest to scientists, health care pundits and faddists; its nutritional and biomedical attributes may be validated, anecdotal or fantasy. Vitamin E is a mixture of tocopherols (TPs) and tocotrienols (T-3s), each class having four substitutional isomers (α-, β-, γ-, δ-). Vitamin E analogues attain only low concentrations in most tissues, necessitating exacting invasive techniques for analytical research. Quantitative positron emission tomography (PET) with an F-18-labeled molecular probe would expedite access to Vitamin E’s biodistributions and pharmacokinetics via non-invasive temporal imaging. (R)-6-(3-[18F]Fluoropropoxy)-2,7,8-trimethyl-2-(4,8,12-trimethyltrideca-3,7,11-trien-1-yl)-chromane ([18F]F-γ-T-3) was prepared for this purpose. [18F]F-γ-T-3 was synthesized from γ-T-3 in two steps: (i) 1,3-di-O-tosylpropane was introduced at C6-O to form TsO-γ-T-3, and (ii) reaction of this tosylate with [18F]fluoride in DMF/K222. Non-radioactive F-γ-T-3 was synthesized by reaction of γ-T-3 with 3-fluoropropyl methanesulfonate. [18F]F-γ-T-3 biodistribution in a murine tumor model was imaged using a small-animal PET scanner. F-γ-T-3 was prepared in 61% chemical yield. [18F]F-γ-T-3 was synthesized in acceptable radiochemical yield (RCY 12%) with high radiochemical purity (>99% RCP) in 45 min. Preliminary F-18 PET images in mice showed upper abdominal accumulation with evidence of renal clearance, only low concentrations in the thorax (lung/heart) and head, and rapid clearance from blood. [18F]F-γ-T-3 shows promise as an F-18 PET tracer for detailed in vivo studies of Vitamin E. The labeling procedure provides acceptable RCY, high RCP and pertinence to all eight Vitamin E analogues. 相似文献
82.
Ivana Brekalo David E. Deliz Leonard J. Barbour Michael D. Ward Tomislav Fri
i K. Travis Holman 《Angewandte Chemie (International ed. in English)》2020,59(5):1997-2002
Guanidinium organosulfonates (GSs) are a large and well‐explored archetypal family of hydrogen‐bonded organic host frameworks that have, over the past 25 years, been regarded as nonporous. Reported here is the only example to date of a conventionally microporous GS host phase, namely guanidinium 1,4‐benzenedisulfonate ( p ‐G2BDS ). p ‐G2BDS is obtained from its acetone solvate, AcMe@ G2BDS , by single‐crystal‐to‐single‐crystal (SC‐SC) desolvation, and exhibits a Type I low‐temperature/pressure N2 sorption isotherm (SABET=408.7(2) m2 g?1, 77 K). SC‐SC sorption of N2, CO2, Xe, and AcMe by p ‐G2BDS is explored under various conditions and X‐ray diffraction provides a measurement of the high‐pressure, room temperature Xe and CO2 sorption isotherms. Though p ‐G2BDS is formally metastable relative to the “collapsed”, nonporous polymorph, np ‐G2BDS , a sample of p ‐G2BDS survived for almost two decades under ambient conditions. np ‐G2BDS reverts to zCO2@ p ‐G2BDS or yXe@ p ‐G2BDS (y,z=variable) when pressure of CO2 or Xe, respectively, is applied. 相似文献
83.
Leonard J. Schulman 《Positivity》2009,13(3):559-574
Muirhead’s majorization inequality was extended by Rado to the case of arbitrary permutation groups. We further generalize
this inequality to compact groups and their linear representations over the reals. We characterize saturation of the inequality,
and describe the saturation condition in detail for the case of actions on Hermitian operators.
Supported in part by the National Science Foundation and the Center for the Mathematics of Information. 相似文献
84.
Aarne Kasikov Alar Gerst Arvo Kikas Leonard Matisen Agu Saar Aivar Tarre Arnold Rosental 《Central European Journal of Physics》2009,7(2):356-362
The resistive response of atomic layer deposited thin epitaxial α-Cr2O3(0 0 1) films, to H2 and CO in air, was studied. The films were covered with Pt nanoislands formed by electron-beam evaporation of a sub-monolayer
amount of the material. The gas measurements were performed at 250°C and 450°C. These temperatures led to different proportion
of chemical states, Pt2+ and Pt4+, to which the Pt oxidized. The modification was ascertained by the X-ray photoelectron spectroscopy method. As a result of
the modification, the response was fast at 250°C, but slowed at 450°C. A disadvantageous abundance of Pt4+ arising at 450°C in air could be diminished by high-vacuum annealing thus restoring the response properties of the system
at 250°C.
相似文献
85.
Atkinson IM Chartres JD Groth AM Lindoy LF Lowe MP Meehan GV 《Chemical communications (Cambridge, England)》2002,(20):2428-2429
A new second generation dendrimer incorporating nine S2N2-donor macrocyclic units that bind nine Pd(II) cations is reported. 相似文献
86.
Removal of or replacement of one of two phenylethyl sidearms on azalariats leads to clear evidence for cation-pi interactions with the remaining sidearm. 相似文献
87.
The cation N(2)H(7)(+) has been stabilized in a largely hydrophobic supramolecular environment and characterized in the solid state. The cation is situated in the bowl-shaped cavity of calix[4]arene. All of the hydrogen atoms are clearly discernible owing to high-quality X-ray data as well as lack of disorder and symmetry-imposed ambiguity. It appears that electrostatic interactions play a critical role in stabilizing the structure. 相似文献
88.
89.
J. Leonard und S. L. Malhotra 《Colloid and polymer science》1978,256(7):716
Ohne Zusammenfassung 相似文献
90.
Leonard I. Grossweiner 《Photochemistry and photobiology》1968,8(5):411-417
Abstract— The current status of research on sensitized photoconductive effects in zinc oxide is reviewed. The various types of chemical and spectral photosensitization processes observed in polycrystalline specimens can be explained qualitatively with a generalized electron acceptor molecule (EAM) model. in which electronegative surface agents trap zinc oxide conduction electrons in the dark and illumination causes a release of the trapped electrons. The EAM may be an adsorbed gas or vapor, adsorbed dye molecules, or an aggregated dye film, depending on the particular photoeffect. 相似文献