A DNA nanodevice for mapping sodium at single-organelle resolution.

Cellular sodium ion (Na+) homeostasis is integral to organism physiology. Our current understanding of Na+ homeostasis is largely limited to Na+ transport at the plasma membrane. Organelles may also contribute to Na+ homeostasis; however, the direction of Na+ flow across organelle membranes is unknown because organellar Na+ cannot be imaged. Here we report a pH-independent, organelle-targetable, ratiometric probe that reports lumenal Na+. It is a DNA nanodevice containing a Na+-sensitive fluorophore, a reference dye and an organelle-targeting domain. By measuring Na+ at single endosome resolution in mammalian cells and Caenorhabditis elegans, we discovered that lumenal Na+ levels in each stage of the endolysosomal pathway exceed cytosolic levels and decrease as endosomes mature. Further, we find that lysosomal Na+ levels in nematodes are modulated by the Na+/H+ exchanger NHX-5 in response to salt stress. The ability to image subcellular Na+ will unveil mechanisms of Na+ homeostasis at an increased level of cellular detail.

Use of a "Shoe-Last" Solid-State Template in the Mechanochemical Synthesis of High-Porosity RHO-Zinc Imidazolate.

We report the first use of a nonionic solid (NIS) as a template in mechanosynthesis of a metal-organic framework. Through eight intermolecular C-H···O hydrogen bonds, the macrocyclic MeMeCH2 template predictably functions as a "shoe-last" for the assembly of double-eight rings in the liquid-assisted reaction of ZnO and imidazole (ImH). The resulting new form of ZnIm2 (namely xMeMeCH2@RHO-Zn16Im32) is available in multigram amounts, highly porous, and thermally stable.

Reproducible Synthesis and High Porosity of mer-Zn(Im)2 (ZIF-10): Exploitation of an Apparent Double-Eight Ring Template.

Reproducible synthesis of the elusive merlinoite (mer) topology of zinc imidazolate (mer-Zn(Im)2, or ZIF-10) has been achieved by employing a simple macrocyclic solute-MeMeCH2-as a kinetic template. The corresponding phase-pure material, mer-MeMeCH2@Zn16(Im)32, is confirmed to be porous and exhibits one of the highest experimental surface areas (1893 m(2)/g, BET) yet reported for any ZIF. The X-ray single crystal structure of mer-MeMeCH2@Zn16(Im)32·xsolvent reveals the role of the macrocyle as an 8-fold hydrogen bond acceptor in templating the requisite double-eight rings (d8r) of the mer framework.