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31.
Grotjahn DB Kragulj EJ Zeinalipour-Yazdi CD Miranda-Soto V Lev DA Cooksy AL 《Journal of the American Chemical Society》2008,130(33):10860-10861
The secondary structure of a bifunctional catalyst positions a crucial reactive proton in the final intermediate of anti-Markovnikov alkyne hydration to give an aldehyde. NMR coupling and isotopic labeling studies elucidate the location of this proton and its involvement in hydrogen bonding. 相似文献
32.
Elijah Bultz Makoto Ouchi Mitsuo Sawamoto Michael F. Cunningham 《Journal of polymer science. Part A, Polymer chemistry》2019,57(3):305-312
This work reports the use of cocatalysts in addition to “smart” ruthenium catalysts for Ru‐mediated reversible deactivation radical polymerization (RDRP) in miniemulsion, allowing for the synthesis of final products with significantly reduced residual metal. Using amine cocatalysts in miniemulsion allows for high conversions (> 90%) in under 10 h. Two forms of ferrocene cocatalysts are also used, including “smart” thermoresponsive PEGylated ferrocene derivatives (FcPEG) and ferrocene containing surfactants (FcTMA). Using “smart” thermoresponsive cocatalyst at low concentrations, rate enhancements in BMA and BzMA polymerizations are observed, with good catalyst removability. Using the FcTMA cocatalyst surfactant, increasing monomer hydrophobicity is shown to increase the polymerization rate and initiator efficiency. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 305–312 相似文献
33.
Sun Jun Park Jushin Kim Jaehwan Kim Yoowon Kim Elijah Hwejin Lee Hyeon Jeong Kim Siwon Kim Byungeun Kim Rium Kim Ji Won Choi Jong-Hyun Park Ki Duk Park 《Molecules (Basel, Switzerland)》2022,27(9)
Sphingosine-1-phosphate-1 (S1P1) receptor agonists are well-known drugs for treating multiple sclerosis (MS) caused by autoreactive lymphocytes that attack the myelin sheath. Therefore, an effective therapeutic strategy is to reduce the lymphocytes in the blood by inducing S1P1 receptor internalization. We synthesized serinolamide A, a natural product of the sea, and performed S1P1 receptor internalization assay to evaluate functionally antagonistic S1P1 receptor agonist activity. In order to synthesize derivatives with better efficacy than serinolamide A and B, new derivatives were synthesized by introducing the phenyl ring moiety of fingolimod. Among them, compounds 19 and 21 had superior S1P1 agonistic effects to serinolamide. We also confirmed that compound 19 effectively inhibited lymphocyte outflow in peripheral lymphocyte count (PLC) assay. 相似文献
34.
35.
Elijah Liflyand 《Journal of Fourier Analysis and Applications》2014,20(5):934-946
An old problem on absolute convergence of the re-expansion in the sine (cosine) Fourier series of an absolutely convergent cosine (sine) Fourier series is extended to the non-periodic case (Fourier transforms). Necessary and sufficient conditions are given as relations between the Fourier transforms and their Hilbert transforms. Sufficient conditions for integrability of the Hilbert transform are obtained. 相似文献
36.
A colloidal synthesis method was developed to produce face centered cubic (fcc) Cu nanoparticles in the presence of surfactants
in an organic solvent under an Ar environment. Various synthetic conditions were explored to control the size of the as-prepared
nanoparticles by changing the precursor, varying the amount of surfactants, and tuning the reaction temperature. Transmission
electron microscopy (TEM), selected-area electron diffraction, and high-resolution TEM were used as the main characterization
tools. Upon exposure to air, these nanoparticles are oxidized at different levels depending on their sizes: (1) an inhomogeneous
layer of fcc Cu2O forms at the surface of Cu nanoparticles (about 30 nm); (2) Cu nanoparticles (about 5 nm) are immediately oxidized into
fcc Cu2O nanoparticles (about 6 nm). The occurrence of these different levels of oxidization demonstrates the reactive nature of
Cu nanoparticles and the effect of size on their reactivity. Furthermore, utilization of their chemical reactivity and conversion
of spherical Cu nanoparticles into CuS nanoplates through the nanoscale Kirkendall effect were demonstrated. The oxidization
and sulfidation of Cu nanoparticles were compared. Different diffusion and growth behaviors were involved in these two chemical
transformations, resulting in the formation of isotropic Cu2O nanoparticles during oxidization and anisotropic CuS nanoplates during sulfidation.
相似文献
37.
Grewia gum is a naturally occurring polysaccharide which has potential as a pharmaceutical excipient. Differential scanning
calorimetry and Fourier transform infrared (FT-IR) spectroscopy techniques were used to examine the thermal and molecular
behaviours, respectively, of mixtures of grewia gum with cimetidine, ibuprofen or standard excipients, to assess potential
interactions. No disappearance or broadening of the melting endotherm was seen with cimetidine or ibuprofen. Similarly, there
was no interaction between grewia gum and the standard excipients tested. The results obtained using thermal analyses were
supported by FT-IR analysis of the material mixtures. Grewia gum is an inert natural polymer which can be used alone or in
combination with other excipients in the formulation of pharmaceutical dosage forms. 相似文献
38.
Ying Jin Anthony P. Kotula Angela R. Hight Walker Kalman B. Migler Young Jong Lee 《Journal of Raman spectroscopy : JRS》2016,47(11):1375-1384
We use moving‐window two‐dimensional correlation spectroscopy (MW‐2DCOS) for phase‐specific Raman analysis of the n‐alkane (C21H44) during melting from the crystalline solid phase to the intermediate rotator phase and to the amorphous molten phase. In MW‐2DCOS, individual peak‐to‐peak correlation analysis within a small subset of spectra provides both temperature‐resolved and spectrally disentangled Raman assignments conducive to understanding phase‐specific molecular interactions and chain configurations. We demonstrate that autocorrelation MW‐2DCOS can determine the phase transition temperatures with a higher resolving power than commonly used analysis methods including individual peak intensity analysis or principal component analysis. Besides the enhanced temperature resolving power, we demonstrate that asynchronous 2DCOS near the orthorhombic‐to‐rotator transition temperature can spectrally resolve the two overlapping peaks embedded in the Raman CH2 twisting band in the orthorhombic phase, which had been only predicted but not observed because of thermal broadening near the melting temperature. Published 2016. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
39.
40.
Ustinov A Weissman H Shirman E Pinkas I Zuo X Rybtchinski B 《Journal of the American Chemical Society》2011,133(40):16201-16211
Self-assembly in aqueous medium is of primary importance and widely employs hydrophobic interactions. Yet, unlike directional hydrogen bonds, hydrophobic interactions lack directionality, making difficult rational self-assembly design. Directional hydrophobic motif would significantly enhance rational design in aqueous self-assembly, yet general approaches to such interactions are currently lacking. Here, we show that pairwise directional hydrophobic/π-stacking interactions can be designed using well-defined sterics and supramolecular multivalency. Our system utilizes a hexasubstituted benzene scaffold decorated with 3 (compound 1) or 6 (compound 2) amphiphilc perylene diimides. It imposes a pairwise self-assembly mode, leading to well-defined supramolecular polymers in aqueous medium. the assemblies were characterized using cryogenic electron microscopy, small-angle X-ray scattering, optical spectroscopy, and EPR. Supramolecular polymerization studies in the case of 2 revealed association constants in 10(8) M(-1) range, and significant enthalpic contribution to the polymerization free energy. The pairwise PDI motif enables exciton confinement and localized emission in the polymers based on 1 and 2's unique photonic behavior, untypical of the extended π-stacked systems. Directional pairwise hydrophobic interactions introduce a novel strategy for rational design of noncovalent assemblies in aqueous medium, and bring about a unique photofunction. 相似文献