Synthesis, characterization and antimicrobial investigation of Rh(III), Ru(III) and Ag(I) complexes with some derivatives of 3-amino-2-thioxo-2,3-dihydroquinazolin-4(1H)-ones

The reaction of 2,3-disubstituted mercapto quinazolines with 2-hydroxy benzaldehyde (HBAMQ) (1), 2-hydroxy naphthaldehyde (HNAMQ) (2), pyridine-2-carboxaldehyde (PMAMQ) (3) and thiophen-2-carboxaldehyde (TMAMQ) (4), and with metals like Rh(III), Ru(III), and Ag(I) in the presence of piperidine resulted in the formation of their respective complexes by physicochemical methods. The newly synthesized complexes were characterized by elemental analysis, magnetic data, and spectroscopic techniques like UV-Visible, IR and 1H NMR, respectively. These compounds were also evaluated for their antimicrobial activities

Zn(II), Cd(II) and Hg(II) metal complexes of 2-aminonicotinaldehyde: Synthesis, crystal structure, biological evaluation and molecular docking study

In this report, the ligand, 2-aminonicotinaldehyde (ANA) and its metal complexes Zn(ANA)(2)Cl-2], Cd (ANA)(2)Cl-2] and Hg(ANA)(2)Cl-2] have been synthesized and characterized by analytical and various spectroscopic (IR, Electronic, H-1 and C-13 NMR) studies. The single crystal X-ray diffraction studies of ANA and Zn(ANA)(2)Cl-2] complex have been discussed. It was found that intra/intermolecular hydrogen bonding exists in both compounds and N-atom of pyridine ring of ANA coordinated to the metal ion in tetrahedral fashion. Metal chlorides, ANA and its complexes were subjected to biological screening, antioxidant, in vitro cytotoxicity and EGFR (Epidermal growth factor receptor) targeting molecular docking studies which indicated the synergistic effect of metal complexes on the biological activity than the free ligand and metal chlorides. (C) 2017 Elsevier B.V. All rights reserved

A Functional Zn(II) Metallacycle Formed from an N‑Heterocyclic Carbene Precursor: A Molecular Sensor for Selective Recognition of Fe³⁺ and IO₄^– Ions

We have reported the synthesis and structural characterization of a unique Zn­(II) metallacycle (<b>1</b>) and its utilization as a fluorescent probe for the shape-specific selective recognition (turn-off) of Fe³⁺ and IO₄^– ions. The relevant Stern–Volmer graphs indicate that the recognitions of Fe³⁺ and IO₄^– ions are examples of diphasic and monophasic quenchings, respectively. The title metallacycle has been prepared by the reaction of a novel N-heterocyclic carbene precursor, 1,3-bis­(2,6-diisopropyl-4-(pyridin-4-yl)­phenyl)-1<i>H</i>-imidazol-3-ium chloride/bromide (<b>L</b>), and zinc­(II) chloride salt. Notably, the ligand itself did not show any type of recognition for any ions. DFT calculations were performed on <b>L</b> and metallacycle <b>1</b> using the geometric parameters, obtained from their single-crystal X-ray diffraction data, to understand the electronic structures of the ligand and macrocycle. The detection limit for the recognition of the Fe³⁺ ion was determined to be 2.5 × 10^–6 mol/L, and that for IO₄^– ion was found to be 6.3 × 10^–5 mol/L

Reduced voltage sensitivity in a K+-channel voltage sensor by electric field remodeling

Propagation of the nerve impulse relies on the extreme voltage sensitivity of Na+ and K+ channels. The transmembrane movement of four arginine residues, located at the fourth transmembrane segment (S4), in each of their four voltage-sensing domains is mostly responsible for the translocation of 12 to 13 eo across the transmembrane electric field. Inserting additional positively charged residues between the voltage-sensing arginines in S4 would, in principle, increase voltage sensitivity. Here we show that either positively or negatively charged residues added between the two most external sensing arginines of S4 decreased voltage sensitivity of a Shaker voltage-gated K+-channel by up to ≈50%. The replacement of Val363 with a charged residue displaced inwardly the external boundaries of the electric field by at least 6 Å, leaving the most external arginine of S4 constitutively exposed to the extracellular space and permanently excluded from the electric field. Both the physical trajectory of S4 and its electromechanical coupling to open the pore gate seemed unchanged. We propose that the separation between the first two sensing charges at resting is comparable to the thickness of the low dielectric transmembrane barrier they must cross. Thus, at most a single sensing arginine side chain could be found within the field. The conserved hydrophobic nature of the residues located between the voltage-sensing arginines in S4 may shape the electric field geometry for optimal voltage sensitivity in voltage-gated ion channels