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31.
32.
Studies of the structural, physical, and chemical properties of the lanthanide(III) complexes of DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) and related ligands are often complicated by the presence of two coordination isomers in solution. Since these coordination isomers are in exchange and cannot be separated, many techniques offer information only on the weighted average of the two isomers. Lanthanide ion complexes formed with the ligands S(RRRR)NO2BnDOTMA and S(SSSS)NO2BnDOTMA preferentially adopt only one of the two common coordination isomers in solution, so the ytterbium complexes of these ligands offer a unique opportunity to study the near-infrared circular dichroism (NIR-CD) characteristics of each coordination geometry in isolation. The spectra acquired support many of the conclusions and assumptions of previous studies and demonstrate that this spectroscopy is particularly sensitive to the distortion of the coordination polyhedron. This will have particularly relevant consequences when studying achiral YbDOTA-like systems forming labile adducts with (chiral) hosts and receptors. 相似文献
33.
The energy spectrum of the e-μ events from τ-decay is analyzed in an attempt to rule out the possibility that the ντ is spin- independent of the observation of the pionic decay mode. While spin- cannot be completely ruled out in this way, it is only viable for a fairly narrow range of values of a Michel parameter. 相似文献
34.
Douglas McHugh Sherry SJ Hu Neta Rimmerman Ana Juknat Zvi Vogel J Michael Walker Heather B Bradshaw 《BMC neuroscience》2010,11(1):44
Background
Microglia provide continuous immune surveillance of the CNS and upon activation rapidly change phenotype to express receptors that respond to chemoattractants during CNS damage or infection. These activated microglia undergo directed migration towards affected tissue. Importantly, the molecular species of chemoattractant encountered determines if microglia respond with pro- or anti-inflammatory behaviour, yet the signaling molecules that trigger migration remain poorly understood. The endogenous cannabinoid system regulates microglial migration via CB2 receptors and an as yet unidentified GPCR termed the 'abnormal cannabidiol' (Abn-CBD) receptor. Abn-CBD is a synthetic isomer of the phytocannabinoid cannabidiol (CBD) and is inactive at CB1 or CB2 receptors, but functions as a selective agonist at this Gi/o-coupled GPCR. N-arachidonoyl glycine (NAGly) is an endogenous metabolite of the endocannabinoid anandamide and acts as an efficacious agonist at GPR18. Here, we investigate the relationship between NAGly, Abn-CBD, the unidentified 'Abn-CBD' receptor, GPR18, and BV-2 microglial migration. 相似文献35.
Nitrogen isotope fractionation factors (α) measured and estimated from the volatilisation of ammonia from water at pH 9.2 and pH 8.5 总被引:1,自引:0,他引:1
ABSTRACTThis paper examines the nitrogen isotope fractionation factors (α) associated with the volatilisation of ammonia from water under controlled conditions at two pH values (8.5 and 9.2). This experiment assumed the continuous removal of ammonia at a single purge rate of 10?mL air min?1. The fractionation resulting from the removal of total ammonia from the water into an acid trap was named the observed isotope fractionation factor (αobs), and it was measured as 1.019 (±0.0025) at pH 8.5 and 1.030 (±0.0025) at pH 9.2. The observed isotope fractionation factor includes the equilibrium isotope fractionation factor (αeq) and the kinetic isotope fractionation factor (αkin), each one mathematically derived from the experimental data. The equilibrium and kinetic isotope fractionation factors were estimated as αeq?=?1.036 (±0.0014) and αkin?=?1.050 (±0.003), respectively. Our results are compared to other previously measured and estimated fractionation factors. 相似文献
36.
Synthesis of Spirocyclic Ethers by Enantioselective Copper‐Catalyzed Carboetherification of Alkenols 下载免费PDF全文
Shuklendu D. Karyakarte Chanchamnan Um Ilyas A. Berhane Prof. Sherry R. Chemler 《Angewandte Chemie (International ed. in English)》2018,57(39):12921-12924
Spirocyclic ethers can be found in bioactive compounds. This copper‐catalyzed enantioselective alkene carboetherification provides 5,5‐, 5,6‐ and 6,6‐spirocyclic products containing fully substituted chiral carbon centers with up to 99 % enantiomeric excess. This reaction features the formation of two rings from acyclic substrates, 1,1‐disubstituted alkenols functionalized with either arenes, alkenes, or alkynes, and clearly constitutes a powerful way to synthesize chiral spirocyclic ethers. 相似文献
37.
The enantioselective synthesis of (S)-(+)-tylophorine, a potent cancer cell growth inhibitor, has been accomplished in eight steps from commercially available 3,4-dimethoxybenzyl alcohol. A copper (II)-catalyzed enantioselective intramolecular alkene carboamination was employed as the key step to construct the chiral indolizidine ring. 相似文献
38.
Wu Y Zhou Y Ouari O Woods M Zhao P Soesbe TC Kiefer GE Sherry AD 《Journal of the American Chemical Society》2008,130(42):13854-13855
Linear polymers of PARACEST agents were prepared by using classical free radical chain polymerization conditions. The Eu3+-polymers exhibited similar intermediate-to-slow water exchange and CEST characteristics as the Eu3+-monomers. This provided an avenue to lower the detection limit of these imaging agents substantially and makes them potentially useful as MRI sensors for molecular imaging. 相似文献
39.
Ratnakar SJ Woods M Lubag AJ Kovacs Z Sherry AD 《Journal of the American Chemical Society》2008,130(1):6-7
The chemical exchange saturation transfer (CEST) efficiency for a series Eu3+-based tetraamide complexes bearing p-substituents on a single coordinating pendant arm is highly sensitive to water exchange rates. The CEST effect increases in the order Me < MeO < F approximately CO2tBu < CN < H. These results show that CEST contrast can be modulated by changes in electron density at a single ligating atom, and this forms the basis of creating imaging agents that respond to chemical oxidation and reduction. 相似文献
40.
Oxidative Conversion of a Europium(II)‐Based T1 Agent into a Europium(III)‐Based paraCEST Agent that can be Detected In Vivo by Magnetic Resonance Imaging 下载免费PDF全文
Dr. Alexander M. Funk Dr. Veronica Clavijo Jordan Prof. A. Dean Sherry Dr. S. James Ratnakar Prof. Zoltan Kovacs 《Angewandte Chemie (International ed. in English)》2016,55(16):5024-5027
The EuII complex of 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) tetra(glycinate) has a higher reduction potential than most EuII chelates reported to date. The reduced EuII form acts as an efficient water proton T1 relaxation reagent, while the EuIII form acts as a water‐based chemical exchange saturation transfer (CEST) agent. The complex has extremely fast water exchange rate. Oxidation to the corresponding EuIII complex yields a well‐defined signal from the paraCEST agent. The time course of oxidation was studied in vitro and in vivo by T1‐weighted and CEST imaging. 相似文献