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111.
Ferreira TM Medronho B Martin RW Topgaard D 《Physical chemistry chemical physics : PCCP》2008,10(39):6033-6038
A lyotropic nonionic lamellar system composed of pentaethyleneglycol mono n-dodecyl ether and D(2)O was studied using natural abundance (13)C NMR under magic-angle spinning. Applying a two-dimensional recoupling method proposed by Dvinskikh (R-PDLF), (1)H-(13)C dipolar couplings were estimated over a range of temperatures (300-335 K), thus enabling analysis of structural changes in the liquid crystalline system. The results obtained are used to correlate the conformation and mobility of local sites in the surfactant molecule with overall changes in the lamellar structure. 相似文献
112.
Rachel Atzmon Ori Cheshnovsky Baruch Raz Joshua Jortner 《Chemical physics letters》1974,29(3):310-313
We report an experimental study of Xe(3P1) → Xe(3P2) electronic quenching by Ar in Xe/Ar mixtures optically excited by the 1470 Å line of Xe. The quenching process was monitored by the observation of the Xe*2 second emission continuum at low Xe pressures. 相似文献
113.
Dr. Rachel Hevey 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(7):2240-2253
Glycans are well established to play important roles at various stages of infection and disease, and ways to modulate these interactions have been sought as novel therapies. The use of native glycan structures has met with limited success, which can be attributed to their characteristic high polarity (e.g., low binding affinities) and inherently poor pharmacokinetic properties (e.g., short drug–target residence times, rapid renal excretion), leading to the development of ′glycomimetics′. Fluorinated drugs have become increasingly common over recent decades, with fluorinated glycomimetics offering some unique advantages. Deoxyfluorination maintains certain electrostatic interactions, while concomitantly reducing net polarity through ′polar hydrophobicity′, improving residence times and binding affinities. Fluorination destabilizes the oxocarbenium transition state associated with metabolic degradation, and can restore exo- and endo-anomeric effects in C-glycosides and carbasugars. Lastly, it has shown great utility in radiotracer development and enhancement of antigenicity in glycan-based vaccines. Owing to synthetic challenges, fluorinated glycomimetics have been somewhat underutilized to date, but methodological improvements will advance their use in glycomimetic drugs. 相似文献
114.
Mary E. Neubert Corresponding author Michael R. Fisch Sandra S. Keast Julie M. Kim Mark C. Lohman Rachel S. Murray 《Liquid crystals》2013,40(7):941-963
The typical sidewalls produced in the fabrication of protrusion electrodes are proposed to create a low voltage (4.5 Vrms) and high transmittance (93%) blue-phase liquid crystal display (BP-LCD). The tilted electrodes produce a strong horizontal electrical field that reduces the operating voltage considerably. The common problem of the ‘dead zones’ is solved by reflecting the light onto the electrodes. In order to estimate the phase retardation of the reflected light, a ray tracing simulation program for anisotropic mediums has been developed. The proposed device is more competitive than vertical field switching based BP-LCD and also, has the advantages of protruded in-plane-switching structures. These facts make this technology a potential candidate for the next generation of BP-LCDs. 相似文献
115.
116.
Rebecca J. Hopkins Rachel Symes Robert M. Sayer Jonathan P. Reid 《Chemical physics letters》2003,380(5-6):665-672
Cavity-enhanced Raman scattering is used to determine the size and composition of multicomponent ethanol/water droplets in the concentration range 7.5–19% ethanol by volume. Under the experimental conditions presented here, the integrated CERS signal from ethanol shows an exponential increase with increase in ethanol concentration when compared with the integrated intensity of the water band. The calibration is shown to be invariant with particle size over the droplet radius range 20–35 μm. In addition to providing a method for determining particle size and composition, initial studies show that the evaporation dynamics of these multicomponent droplets can be probed by CERS. 相似文献
117.
Davies SG Díez D El Hammouni MM Garner AC Garrido NM Long MJ Morrison RM Smith AD Sweet MJ Withey JM 《Chemical communications (Cambridge, England)》2003,(19):2410-2411
Comparison of the kinetic and parallel kinetic resolutions of methyl (RS)-5-tert-butyl-cyclopentene-1-carboxylate allows for the efficient synthesis of both (1R,2S,5S)- and (1S,2R,5R)-enantiomers of methyl 2-amino-5-tert-butyl-cyclopentane-1-carboxylate. 相似文献
118.
Botta M Aime S Barge A Bobba G Dickins RS Parker D Terreno E 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(9):2102-2109
The (1)H and (17)O NMR relaxometric properties of two cationic complexes formed by Gd(III) with a macrocyclic heptadentate triamide ligand, L(1), and its Nmethylated analogue, L(2), have been investigated in aqueous media as a function of pH, temperature and magnetic field strength. The complexes possess two water molecules in their inner coordination sphere for which the rate of exchange has been found to be sensibly faster for the Nmethylated derivative and explained in terms of electronic effects (decrease of the charge density at the metal center) and perturbation of the network of hydrogen-bonded water molecules in the outer hydration sphere. The proton relaxivity shows a marked dependence from pH and decreases of about six units in the pH range 6.5 to 9.0. This has been accounted for by the displacement of the two water molecules by dissolved carbonate which acts as a chelating anion. The formation of ternary complexes with lactate, malonate, citrate, acetate, fluoride and hydrogenphosphate has been monitored by (1)H NMR relaxometric titrations at 20 MHz and pH 6.3 and the value of the affinity constant, K, and of the relaxivity of the adducts could be obtained. Lactate, malonate and citrate interact strongly with the complexes (log K > or =3.7) and coordinate in a bidendate mode by displacing both water molecules. Larger affinity constants have been measured for GdL(2). Acetate, fluoride and hydrogenphosphate form monoaqua ternary complexes which were investigated in detail with regard to their relaxometric properties. The NMR dispersion (NMRD) profiles indicate a large contribution to the relaxivity of the adducts from water molecules belonging to the second hydration shell of the complexes and hydrogen-bonded to the anion. A VT (17)O NMR study has shown a marked increase of the rate of water exchange upon binding which is explained by coordination of the anion in an equatorial site, thus leaving the water molecule in an apical position, more accessible for interactions with the solvent molecules of the second hydration shell which facilitate the exchange process. 相似文献
119.
Rachel L. Weller 《Tetrahedron letters》2004,45(30):5807-5810
Ethyl (E)-4,5-dibromo-2-pentenoate readily reacts with an assortment of primary amines in the presence of DBU to afford the corresponding conjugated aziridines in good to moderate yields. That the reaction is compatible with a nucleoside-derived amine suggests a broad scope of application. 相似文献
120.
Dr. Thomas G. Hayhow Rachel E. A. Borrows Dr. Coura R. Diène Gary Fairley Dr. Charlene Fallan Dr. Shaun M. Fillery Dr. James S. Scott Dr. David W. Watson 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(70):16818-16823
A palladium-catalysed Buchwald–Hartwig amination for lenalidomide-derived aryl bromides was optimised using high throughput experimentation (HTE). The substrate scope of the optimised conditions was evaluated for a range of alkyl- and aryl- amines and functionalised aryl bromides. The methodology allows access to new cereblon-based bifunctional proteolysis targeting chimeras with a reduced step count and improved yields. 相似文献