2 research outputs found

    Synthesis and Characterization of a Mesogen-Jacketed Polyelectrolyte

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    In an attempt to construct a new kind of rodlike polyelectrolyte, poly­[sodium 2,5-bis­(4′-sulfophenyl)­styrene] (PSBSS) was prepared from its precursor, poly­[2,5-bis­(4′-neopentylsulfophenyl)­styrene] (PBNSS), which was polymerized by atom transfer radical polymerization. Small-angle X-ray scattering (SAXS) results demonstrate that PBNSS exhibits a hexagonal columnar phase and PSBSS exhibits a smectic A phase in bulk. The conformation of PSBSS in the aqueous solution is cylindrical, and the length and the diameter of the cylinder are ca. 25 nm and ca. 2.4 nm, respectively. The persistence length (<i>l</i><sub>p</sub>) of the PSBSS chain in the aqueous solution is 11.50 ± 0.09 nm calculated by fitting the SAXS profile with the modified wormlike chain model. The conformation, the maximum length, and the <i>l</i><sub>p</sub> of the chain are only weakly dependent on the concentration of the added salt. These results indicate that we have successfully obtained a new kind of polyelectrolyte with a highly rigid chain, a high charge density, and a narrow molecular weight distribution, which can serve as a new model macromolecule in studying rodlike polyelectrolytes

    Ratiometric Fluorescent Sensing of pH Values in Living Cells by Dual-Fluorophore-Labeled i‑Motif Nanoprobes

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    We designed a new ratiometric fluorescent nanoprobe for sensing pH values in living cells. Briefly, the nanoprobe consists of a gold nanoparticle (AuNP), short single-stranded oligonucleotides, and dual-fluorophore-labeled i-motif sequences. The short oligonucleotides are designed to bind with the i-motif sequences and immobilized on the AuNP surface via Au–S bond. At neutral pH, the dual fluorophores are separated, resulting in very low fluorescence resonance energy transfer (FRET) efficiency. At acidic pH, the i-motif strands fold into a quadruplex structure and leave the AuNP, bringing the dual fluorophores into close proximity, resulting in high FRET efficiency, which could be used as a signal for pH sensing. The nanoprobe possesses abilities of cellular transfection, enzymatic protection, fast response and quantitative pH detection. The <i>in vitro</i> and intracellular applications of the nanoprobe were demonstrated, which showed excellent response in the physiological pH range. Furthermore, our experimental results suggested that the nanoprobe showed excellent spatial and temporal resolution in living cells. We think that the ratiometric sensing strategy could potentially be applied to create a variety of new multicolor sensors for intracellular detection
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