A 3,7-diazabicyclo[3.3.1]nonane linking to two melamines is a unique transmembrane H /Cl carrier. In the solid state, the V-shaped compound forms a HCl-bound zig-zag network through cooperative protonation and hydrogen bond interactions. In the lipid membrane, the receptor forms a dimeric self-assembly involving multiple H and Cl leading to the efficient transport of the acid. The pH-dependent Cl efflux observed for the compound was rationalized based on a gradual protonation model that confers an active transmembrane carrier at physiological pH.
An
amphiphilic pyrene derivative exhibiting unusually stable excimer
emission due to strong aggregation is presented. The aggregated system
served as an intelligent sensor for metal ions and nitro explosives
in aqueous media. The excimer displayed excellent selectivity toward
Cu2+ among the tested cations. The observation
was interpreted on the basis of chelation of metal ions involving
the hydroxyl and amino groups of two molecules, leading to the ligand-to-metal
charge-transfer (CT) process. The excimer was further applied for
the cell imaging of Cu2+ ions. Also, while treating the
excimer with various nitro explosives, it displayed efficient 2,4,6-trinitrophenol
sensing, corroborating mainly the CT process from pyrene to the analyte
due to intercalation of the analyte within pyrene.
Acyclic αγα-tripeptides derived from fluorinated-furanoid sugar amino acid frameworks act as reverse-turn inducers with a U-shaped conformation, whereas the corresponding nonfluorinated αγα-tripeptides show random peptide conformations. The NMR studies showed the presence of bifurcated weak intramolecular hydrogen bonding (F···HN) and N···F charge-dipole attraction compel the amide carbonyl groups to orient antiperiplanar to the C-F bond, thus, demonstrating the role of the fluorine substituent in stabilizing the U-shaped conformation. The NOESY data indicate that the U-shaped tripeptides self-assembly formation is stabilized by the intermolecular hydrogen bonding between C═O···HN with antiparallel orientation. This fact is supported by ESI-MS data, which showed mass peaks up to the pentameric self-assembly, even in the gas phase. The morphological analysis by FE-SEM, on solid samples, showed arrangement of fibers into nanorods. The antiparallel self-assembled pore of the fluorinated tripeptides illustrates the selective ion-transport activity. The experimental findings were supported by DFT studies.
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