Multistimuli-Responsive Hydrolytically Stable “Smart” Mercury(II) Coordination Polymer

A new one-dimensional double chain photoluminescent Hg­(II) coordination polymer (CP), {[Hg­(L)2]·(ClO4)2}n (1), was synthesized using a benzimidazole-appended tripodal tridentate ligand, 1,3,5-tris­(benzimidazolylmethyl)­benzene (L). The dynamic and flexible framework of 1 allows it to be entitled as first Hg­(II)-based CP belonging to the rare category of CPs that exhibit multistimuli-responsive photoluminescence sensing properties and called as “smart” material. The sensitivity of this material via luminescence quenching method showing “turn off” behavior to a range of stimuli, including anions, solvents, and nitroaromatic compounds (NACs), offers more fine-grained control over its properties. 1 can easily adjust its channel dimensions to encapsulate different guest anions forming complete/partial anion-exchanged materials 1A–1B/1C–1E using NO3–, BF4–, OTf–, OTs–, and PF6– anions, respectively. Reversible (1A and 1B) and irreversible (1C–1E) anion exchange behaviors were observed for the complete and partial anion-exchanged products, respectively. The noteworthy feature of the anion-exchanged compounds is their anion-triggered luminescent behavior depending on different properties of anions.The excellent emission in water and high hydrolytic stability of 1 allows its use for rapid and efficient fluorescence-based detections of NACs in aquatic system. The uncoordinated pendant benzimidazole moiety in 1 serves as Lewis basic recognition site for trinitrophenol (TNP) detection, and along with electron- and energy-transfer mechanisms, 1 forms a luminescent probe for detection of TNP with low detection limits (0.55 ppm), exhibiting excellent photostability and recyclability. 1 also represents the first reported Hg­(II)-based sensory CP material that can discriminate nitrophenol and nitroaniline isomers through fluorescence sensing

A Hexameric Hexagonal Organotin Macrocycle. Supramolecular Entrapment of an Iodide–Iodide Short Contact

A hexanuclear hexagonal organotin macrocycle [(<i>n</i>-Bu₃Sn)₆­(μ-L)₆(I^–)₂­(MeOH)₆] (<b>1</b>) was synthesized in a 1:1 reaction of (<i>n</i>-Bu₃Sn)₂O and 4,5-dicarboxy-1,3-dimethyl-1<i>H</i>-imidazol-3-ium iodide (LH₂I). The molecular structure of <b>1</b> reveals that it is a 42-membered hexatin macrocycle possessing a <i>C</i>₃ (pseudo-<i>S</i>₆) symmetry. The alternate up–down arrangement of imidazolium units allows the molecule to assume a <i>chair</i> topology. The hexagonal packing of these macrocycles, in the solid-state, results in nanoscale one-dimensional channels which entrap two I^– ions in close proximity (∼3.7 Å) as a result of various supramolecular interactions

A Hexameric Hexagonal Organotin Macrocycle. Supramolecular Entrapment of an Iodide–Iodide Short Contact

A hexanuclear hexagonal organotin macrocycle [(<i>n</i>-Bu₃Sn)₆­(μ-L)₆(I^–)₂­(MeOH)₆] (<b>1</b>) was synthesized in a 1:1 reaction of (<i>n</i>-Bu₃Sn)₂O and 4,5-dicarboxy-1,3-dimethyl-1<i>H</i>-imidazol-3-ium iodide (LH₂I). The molecular structure of <b>1</b> reveals that it is a 42-membered hexatin macrocycle possessing a <i>C</i>₃ (pseudo-<i>S</i>₆) symmetry. The alternate up–down arrangement of imidazolium units allows the molecule to assume a <i>chair</i> topology. The hexagonal packing of these macrocycles, in the solid-state, results in nanoscale one-dimensional channels which entrap two I^– ions in close proximity (∼3.7 Å) as a result of various supramolecular interactions

Effect of tetracycline family of antibiotics on actin aggregation, resulting in the formation of Hirano bodies responsible for neuropathological disorders

Actin, an ATPase superfamily protein, regulates some vital biological functions like cell locomotion, cytokinesis, synaptic plasticity and cell signaling in higher eukaryotes, and is dependent on the dynamics of actin polymerization process. Impaired regulation of actin polymerization has been implicated in the formation and deposition of rod-like paracrystalline structures called as Hirano bodies in neuronal cells of patients suffering from Alzheimer’s disease, Pick’s disease, Guam amyotrophic lateral sclerosis and parkinsonism–dementia complex. Aggregation of actin forming amorphous deposition in the brain cells is also associated with chronic alcoholism and aging of the neurons. In the current article, we propose the breaking of the highly amorphous and dysregulated actin aggregates using generic compounds like tetracycline, oxytetracycline, doxycycline and minocycline which are used as antibiotics against tuberculosis and infection caused due to various Gram-negative bacteria. We have investigated the effect and affinity of binding of these four compounds to that of actin aggregates using 90° light scattering, size exclusion chromatography, dynamic light scattering, circular dichroism, scanning electron microscopy, transmission electron microscopy imaging and kinetic analysis. The isothermal calorimetric measurements showed that the binding constant for the cycline family molecules used in this study range from 9.8 E4 M−1 to 1.3 E4 M−1. To understand the in vivo effect, we also studied the effect of these drugs on Saccharomyces cerevisiae Δend3 mutant cells. Our data suggest that these generic compounds can plausibly be used for the treatment of various neurodegenerative diseases occurring due to Hirano body formation in brain cells. Communicated by Ramaswamy H. Sarma</p