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Carbonic anhydrases (CAs) catalyze the physiological hydration of carbon dioxide and are among the most intensely studied pharmaceutical target enzymes. A hallmark of CA inhibition is the complexation of the catalytic zinc cation in the active site. Human (h) CA isoforms belonging to different families are implicated in a wide range of diseases and of very high interest for therapeutic intervention. Given the conserved catalytic mechanisms and high similarity of many hCA isoforms, a major challenge for CA-based therapy is achieving inhibitor selectivity for hCA isoforms that are associated with specific pathologies over other widely distributed isoforms such as hCA I or hCA II that are of critical relevance for the integrity of many physiological processes. To address this challenge, we have attempted to predict compounds that are selective for isoform hCA IX, which is a tumor-associated protein and implicated in metastasis, over hCA II on the basis of a carefully curated data set of selective and nonselective inhibitors. Machine learning achieved surprisingly high accuracy in predicting hCA IX-selective inhibitors. The results were further investigated, and compound features determining successful predictions were identified. These features were then studied on the basis of X-ray structures of hCA isoform-inhibitor complexes and found to include substructures that explain compound selectivity. Our findings lend credence to selectivity predictions and indicate that the machine learning models derived herein have considerable potential to aid in the identification of new hCA IX-selective compounds.

The employment of the hexyl-substituted anion [HexCB11 Cl11 ]- allowed the synthesis of a ZnII species, Zn[HexCB11 Cl11 ]2 , 3, in which the Zn2+ cation is only weakly coordinated to two carborate counterions and that is soluble in low polarity organic solvents such as bromobenzene. DOSY NMR studies show the facile displacement of at least one of the counterions, and this near nakedness of the cation results in high catalytic activity in the hydrosilylation of 1-hexene and 1-methyl-1cyclohexene. Fluoride ion affinity (FIA) calculations reveal a solution Lewis acidity of 3 (FIA=262.1 kJ mol-1 ) that is higher than that of the landmark Lewis acid B(C6 F5 )3 (FIA=220.5 kJ mol-1 ). This high Lewis acidity leads to a high activity in catalytic CO2 and Ph2 CO reduction by Et3 SiH and hydrogenation of 1,1-diphenylethylene using 1,4-cyclohexadiene as the hydrogen source. Compound 3 was characterized by multinuclear NMR spectroscopy, mass spectrometry, single crystal X-ray diffraction, and DFT studies.

The zinc cation in the structure has a N2O3 coordination set, arranged in a trigonal–bipyramidal configuration. The bridging mode of the organic ligands leads to the formation of a polymeric layer structure parallel to the ab plane., The crystal structure of the title polymer, {[Zn(C8H4O6S)(C10H8N2S)(H2O)]·0.26H2O}n, is characterized by a layered arrangement parallel to the ab plane. The zinc cation is five-coordinated in a slightly distorted trigonal–bipyramidal coordination environment defined by two pyridine ligands, two carboxyl­ate groups of two thio­phene di­carboxyl­ate ligands, and by one water mol­ecule. The ethyl­ene bridge in the dioxine ligand is disordered over two sets of sites [occupancy ratio 0.624 (9):0.376 (9)]. Several hydrogen-bonding inter­actions of the types O—H⋯O, C—H⋯O, C—H⋯S and C—H⋯N ensure the cohesion within the crystal structure.

A new imidazolium macrocycle based on tetraphenylethylene (TPE) has been synthesized. This positively charged macrocycle showed a typical aggregation-induced emission (AIE) effect but fluorescence emission could not be induced by common inorganic anions in aqueous solution, including pyrophosphate bearing four negative charges. However, in the presence of a half equivalent of zinc(II) ions, the addition of pyrophosphate anions could arouse a strong fluorescence while other common inorganic anions gave almost no response. The macrocycle has an inherent cavity with the correct size for binding a pyrophosphate anion, so that the pyrophosphate anion can be easily aggregated together with the macrocycle and a zinc cation, which selectively triggers a turn-on fluorescence.

International audience; We report the solid-state structure of an unexpected trinuclear zinc dimeric porphyrin complex resulting of zinc insertion into a single strap porphyrin. The latter bears an overhanging carboxylic acid which usually interacts with metal cations either in out-of-plane (OOP) or in hanging-atop (HAT) coordination mode by changing its location above the porphyrin coordination site. However, in the present studies, the overhanging carboxylic group acts as a bidentate ligand and binds the OOP-bound zinc cation together with another zinc cation bridging two porphyrin units.

Basic properties of bis[5-(3-oxyphenyl)-2,8,12,18-tetrabutyl-3,7,13,17-tetramethylporphyrinyl]-3,6,9-trioxyundecane-1,11 and bis[5-(3-oxyphenyl)-2,8,12,18-tetrabutyl-3,7,13,17-tetramethylporphyrinyl]-3,6,9,12-tetraoxytetradecane-1,14 were studied spectrophotometrically in an ethanol-sulfuric acid system; the influence of the basicity of the inner cycle nitrogen atom on the complexation properties of these polyethylene oxide-substituted porphyrins towards zinc cation in ethanol was considered.

The structure of the title complex, [ZnCl2(C11H9N3)2], comprises two 2-(phenyldiazenyl)pyridine ligands coordinating to a central ZnIIdichloride unitviathe pyridyl N-atom donors, resulting in a slightly distorted tetrahedral geometry. The complex exhibits twofold rotation symmetry, with the rotation axis bisecting the zinc cation. The structure is stabilized by weak intermolecular C—H...Cl interactions [C...Cl = 3.411 (2) and 3.675 (2) Å], connecting neighbouring molecules into layers perpendicular to thecaxis.

The hydrogen bond network influence on the carbonic anhydrase II (CAII) zinc binding site has been studied theoretically by using the semiempirical AM1 method. To this aim, quantum mechanical reduced models of wild-type CAII and several CAII variants have been constructed. We have shown that, when a direct metal ligand donates a hydrogen bond to an indirect metal ligand, the first-shell residues enhance their electrostatic interaction with the zinc cation. Thus, the hydrogen-bond network is able to modulate the zinc binding affinity and the zinc-water pKa.Key words: hydrogen bond network, carbonic anhydrase II, Zn2+ metalloenzyme ligands.

We report the selective modification of cysteine residues engineered in peptides that have two additional cysteine residues as part of a Cys2His2 zinc finger motif. The chemoselective modification is achieved, thanks to the protecting effect exerted by the zinc cation upon coordination with the native cysteines and histidines of the zinc-finger fold. The strategy allows a straightforward synthesis of DNA binding zinc finger constructs We acknowledge the support from the Spanish grants SAF2010-20822-C02, CTQ2009-14431/BQU, CSD2007-00006, the Xunta de Galicia GRC2010/12, GRC2013-041 and INCITE09 209 084PR. J. R. thanks the Fundación Gil Dávila and the Xunta de Galicia and J. M. the Spanish MCINN for their PhD fellowships SI

From a solution of [Zn(H2O)6](NO3)2 and acetyl­enedicarb­oxylic acid in deionized water, single crystals of zinc acetyl­ene­dicarboxyl­ate dihydrate, {[Zn(C4O4)(H2O)2]}n, were obtained by slow evaporation of the solvent. The asymmetric unit consits of one zinc cation which is located on a centre of symmetry, half of an acetyl­enedicarboxyl­ate anion, the anion lying on a twofold axis, and one water mol­ecule in a general position. Thus, zinc is octa­hedrally coordinated by four O atoms of acetyl­enedicarboxyl­ate anions and two water mol­ecules in trans positions. These octa­hedra are connected by dicarboxyl­ate ligands into a three-dimensional network.

Fifteen selected vegetables and fruits were processed by conventional procedures with modified blanching conditions. The texture of blanched and processed samples was determined. Low-Temperature-Long-Time (LTLT) blanching considerably increased the final firmness of sterilized carrot, endive and green bean samples, as well as pasteurized cherry samples. After screening experiments, green bean and endive were chosen for further research. Analysis of variance revealed that LTLT blanching treatments in a blanching solution containing calcium and zinc cation significantly affected the texture and color of processed green bean and endive. The blanching treatments were optimized to improve the texture and color of sterilized green bean and endive.

Energies and structures of six different isomers resulted of complex between glycylglycine dipeptide and zinc cation were calculated at the BLYP and B3LYP levels of theory with 6-311G** and 6-311++G** basis sets. The energies of the glycylglycine-Zn2+different complexes at the BLYP/6-311++G** obtained more stable than another methods. In this method, the most stable complex was zinc cation bound to the two oxygen sites of the glycylglycine zwitterion and acted as a bidentate ligand. The vibrational frequencies, thermodynamic and electronic properties, HOMO, LUMO, and energy gap for the most stable isomer in different solvents were calculated at the BLYP/6-311++G** level of theory.

Di-aza-benzo crown etherp-tert-butyl calix[4]arene (1) has been prepared by hydrogenating the already known Schiff-base precursor (2). The metal ion complexing ability of (1) toward zinc cation is presented. The formation of a 2:1 (Zn: (1) complex and the location of zinc cations were deduced from1H-NMR investigations.

The asymmetric unit of the title compound, [Zn(NCS)(2)(C(6)H(7)N)(2)], consists of one Zn(2+) cation and two thio-cyanate anions, all situated on special positions with site symmetry .m., and one 3-methyl-pyridine ligand. The zinc cation is coordinated by four N atoms of two terminal N-bonded thio-cyanate anions and of two symmetry-related 3-methyl-pyridine co-ligands, defining a slightly distorted tetra-hedral coordination polyhedron.

In the title complex, [Zn(C7H4NO3S)2(C8H22N4)]·H2O or [Zn(sac)2(paen)]·H2O [sac = saccharinate and paen = N,N′-bis(3-aminopropyl)ethylenediamine], the zinc cation is octahedrally coordinated. The equatorial plane of the octahedron is formed by N atoms of the paen ligand, whereas the axial positions are occupied by the carbonyl O atoms of the two sac ligands. One of the sulfonyl groups of the sac ligands shows disorder and was modelled with two different orientations and site occupancies of 0:38 (1):0.62 (1). The molecular packing is stabilized by intermolecular O—H...O and N—H...O hydrogen bonds between water molecules and neighbouring [Zn(sac)2(paen)] molecules, which form chains running parallel to [010]. The crystal used was an inversion twin.

Recently, cadmium-containing additives for plastics have been designated as undesirable environmentally. Prior to this adverse characterization of cadmium derivatives most flexible vinyl in the United States involving severe stabilizer demand during processing or service utilized metal blends based on cadmium salts. As a result many vinyl formulators have been forced to find suitable alternatives. Replacement of a stabilizer composed of specific levels of barium/cadmium salts in flexible vinyl with another containing the same levels of barium/zinc has been found to give dramatically reduced performance in heat stability tests. Results of this study has shown that satisfactory replacement of barium/cadmium/zinc or barium/cadmium systems in flexible vinyl is possible with barium/zinc stabilizers. This replacement appears to depend on higher barium-to-zinc ratios than those utilized in barium/cadmium analogs, use of special ligands that compensate for the smaller sized zinc cation; and prevention of their destruction by inadvertent addition of competitors.

The title compound, [Zn(NO3)(C8H8N2O)2]NO3·H2O, consists of a tris-chelated zinc cation and a nitrate anion, along with an uncoordinated water mol­ecule. These inter­act through O—H⋯O and N—H⋯O hydrogen bonds, giving rise to a three-dimensional network structure. The ZnII ion has an octa­hedral coordination.

The title compound, [Zn(C8H4N4O2)]n, is a coordination polymer prepared by the hydro­thermal reaction of zinc chloride and 3-(1H-tetrazol-5-yl)­benzoic acid. The zinc cation is tetrahedrally coordinated by two N atoms and two O atoms from four ligands, resulting in a three-dimensional framework encapsulating one-dimensional channels.

The asymmetric unit of the title compound, [Zn(NCSe)(2)(C(4)H(4)N(2))(2)](n), consists of one Zn(2+) cation located on a special position with site symmetry 2/m, one seleno-cyanate anion on a mirror plane and one pyrimidine ligand on a twofold rotation axis. The zinc cation is coordinated by six N atoms of four pyrimidine ligands and two N-bonded seleno-cyanate anions in mutually trans orientations within a slightly distorted octa-hedral coordination environment. The Zn atoms are μ-1,3-bridged via the pyrimidine ligands into a polymeric layer extending parallel to (100).