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  1. Abstract

    Macropinosomes are formed by shaping actin-rich plasma membrane ruffles into large intracellular organelles in a phosphatidylinositol 3-kinase (PI3K)-coordinated manner. Here, we utilize lattice lightsheet microscopy and image visualization methods to map the three-dimensional structure and dynamics of macropinosome formation relative to PI3K activity. We show that multiple ruffling morphologies produce macropinosomes and that the majority form through collisions of adjacent PI3K-rich ruffles. By combining multiple volumetric representations of the plasma membrane structure and PI3K products, we show that PI3K activity begins early throughout the entire ruffle volume and continues to increase until peak activity concentrates at the base of the ruffle after the macropinosome closes. Additionally, areas of the plasma membrane rich in ruffling had increased PI3K activity and produced many macropinosomes of various sizes. Pharmacologic inhibition of PI3K activity had little effect on the rate and morphology of membrane ruffling, demonstrating that early production of 3′-phosphoinositides within ruffles plays a minor role in regulating their morphology. However, 3′-phosphoinositides are critical for the fusogenic activity that seals ruffles into macropinosomes. Taken together, these data indicate that local PI3K activity is amplified in ruffles and serves as a priming mechanism for closure and sealing of ruffles into macropinosomes.

     
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  2. Abstract

    In targeting reduced valent lanthanide chalcogenides, we report the first nanoparticle synthesis of the mixed‐valent ferromagnets Eu3S4and EuSm2S4. Using divalent lanthanide halides with bis(trimethylsilyl)sulfide and oleylamine, we prepared nanoparticles of EuS, Eu3S4, EuSm2S4, SmS1.9, and Sm3S4. All nanoparticle phases were identified using powder X‐ray diffraction, transmission electron microscopy was used to confirm morphology and nanoparticle size, and magnetic susceptibility measurements for determining the ordering temperatures and valence. The UV/Vis, Raman and X‐ray photoelectron spectroscopies for each phase were compared. Surprisingly, the phase is influenced by the halide and the reaction temperature, where EuCl2formed EuS while EuI2formed Eu3S4, highlighting the role of kinetics in phase stabilization. Interestingly, at lower temperatures EuI2initially forms EuS, and converts over time to Eu3S4.

     
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  3. Abstract

    In targeting reduced valent lanthanide chalcogenides, we report the first nanoparticle synthesis of the mixed‐valent ferromagnets Eu3S4and EuSm2S4. Using divalent lanthanide halides with bis(trimethylsilyl)sulfide and oleylamine, we prepared nanoparticles of EuS, Eu3S4, EuSm2S4, SmS1.9, and Sm3S4. All nanoparticle phases were identified using powder X‐ray diffraction, transmission electron microscopy was used to confirm morphology and nanoparticle size, and magnetic susceptibility measurements for determining the ordering temperatures and valence. The UV/Vis, Raman and X‐ray photoelectron spectroscopies for each phase were compared. Surprisingly, the phase is influenced by the halide and the reaction temperature, where EuCl2formed EuS while EuI2formed Eu3S4, highlighting the role of kinetics in phase stabilization. Interestingly, at lower temperatures EuI2initially forms EuS, and converts over time to Eu3S4.

     
    more » « less