Self-assembly and molecular recognition are critical processes both in life and material sciences. They usually depend on strong, directional non-covalent interactions to gain specificity and to make long-range organization possible. Most supramolecular constructs are also at least partially governed by topography, whose role is hard to disentangle. This makes it nearly impossible to discern the potential of shape and motion in the creation of complexity. Here, we demonstrate that long-range order in supramolecular constructs can be assisted by the topography of the individual units even in the absence of highly directional interactions. Molecular units of remarkable simplicity self-assemble in solution to give single-molecule thin two-dimensional supramolecular polymers of defined boundaries. This dramatic example spotlights the critical function that topography can have in molecular assembly and paves the path to rationally designed systems of increasing sophistication.
Obligate human pathogenic Neisseria gonorrhoeae are the second most frequent bacterial cause of sexually transmitted diseases. These bacteria invade different mucosal tissues and occasionally disseminate into the bloodstream. Invasion into epithelial cells requires the activation of host cell receptors by the formation of ceramide-rich platforms. Here, we investigated the role of sphingosine in the invasion and intracellular survival of gonococci. Sphingosine exhibited an anti-gonococcal activity in vitro. We used specific sphingosine analogs and click chemistry to visualize sphingosine in infected cells. Sphingosine localized to the membrane of intracellular gonococci. Inhibitor studies and the application of a sphingosine derivative indicated that increased sphingosine levels reduced the intracellular survival of gonococci. We demonstrate here, that sphingosine can target intracellular bacteria and may therefore exert a direct bactericidal effect inside cells.
The reactivity of a literature‐known, ring‐strained bismuth amide cation towards a range of unsymmetric heterocumulene substrates has been investigated. Reactions with ketenes R2C=C=O (R=Me, Ph), isocyanates R'N=C=O, and isothiocyanates R'N=C=S (R’=Ph, 4‐CF3‐C6H4) proceed via facile insertion of the heterocumulene in the Bi−N bond of the cationic bismuth amide. Unexpectedly pronounced differences in the regioselectivity of these insertion reactions have been observed, yielding a rich variety of heterocycle motifs (BiC2NC2, BiC2NCO, BiC2NCS, BiC2NCN), some of which are unprecedented. Parameters that control the regioselectivity of the insertion reactions have been identified and are discussed based on experimental and theoretical investigations. Analytical techniques applied in this work include heteronuclear and two‐dimensional NMR spectroscopy, IR spectroscopy, elemental analysis, single‐crystal X‐ray diffraction analyses, and DFT calculations.
The reactivity of a literature-known, ring-strained cationic bismuth amide toward the unsaturated substrates RNCNR, CS2, and acrylonitrile is reported (R = iPr, Cy, and pTol). Subtle changes in the polarity of the reaction medium (THF vs pyridine) can be exploited to selectively address two different reaction pathways. Either the dinuclear nature of the starting material is preserved, only one substrate molecule per two bismuth atoms is incorporated into the product, and an aryl migration is possible or well-defined mononuclear compounds with a Bi/substrate ration of 1:1 are observed. These findings correlate with an unexpected increase in reactivity of the cationic bismuth species, when the polarity of the solvent is increased from THF to pyridine, and are likely to be connected to the nuclearity of the cationic bismuth amide starting material.
Self-assembly and molecular recognition are critical processes both in life and material sciences. They usually depend on strong, directional non-covalent interactions to gain specificity and to make long-range organization possible. Most supramolecular constructs are also at least partially governed by topography, whose role is hard to disentangle. This makes it nearly impossible to discern the potential of shape and motion in the creation of complexity. Here, we demonstrate that long-range order in supramolecular constructs can be driven by the topography of the individual units even in the absence of directional interactions. Here, molecular units of remarkable simplicity self-assemble in solution to give homogeneous single-molecule thin two-dimensional supramolecular polymers of defined boundaries. This dramatic example spotlights the critical function that topography can have in molecular assembly and paves the path to rationally designed systems of increasing sophistication.
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