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The hydration of [Mg.sup.2+] and [Zn.sup.2+] is examined using molecular dynamics simulations using 3 computational approaches of increasing complexity: the CHARMM nonpolarizable force field based on the TIP3P water model, the Drude polarizable force field based on the SWM4-NDP water model, and a combined QM/MM approach in which the inner coordination sphere is represented using a high-quality density functional theory (DFT) model (PBE/de f2-TZVPP), and the remainder of the bulk water solvent is represented using the polarizable SWM4-NDP water model. The characteristic structural distribution functions (radial, angular, and tilt) are comparedand show very good agreement between the polarizable force field and QM/MM approaches. They predict an average Mg-O distance of 2.11 Å and an Zn-O distance of 2.13 Å, in good agreement with the available experimental neutron scattering and EXAFS data, while the Mg-O distances calculated using the nonpolarizable force field are 0.1 Å too short. [Mg.sup.2+] (aq) and [Zn.sup.2+] (aq) both have a coordination number of 6 and have a remarkably similar octahedral coordination mode, despite the chemical differences between these ions. Thermodynamic integration was used to calculate the relative hydration free energies of these ions (ΔΔ[G.sub.hydr]). The nonpolarizable model is in error by 60 kcal mol-1 and incorrectly predicts that [Mg.sup.2+] has the more negative hydration energy. The Drude polarizable model predicts a ΔΔ[G.sub.hydr] of only -13.2 kcal kcal mol-1, an improvement over the results of the nonpolarizable force field, but still signficantly different than the experimental value of - 30.1 kcal [mol.sup.-1]. The combined QM/MM approach performs much better, predicting a ΔΔ[G.sub.hydr] of -34.8 kcal [mol.sup.-1] in excellent agreement with experiment. These calculations support the experimental observation that [Zn.sup.2+] has more favourable solvation free energy than [Mg.sup.2+] despite having a very similar solvation structure. Key words: ion solvation, [Mg.sup.2+], [Zn.sup.2+], molecular dynamics, polarizable force fields, QM/MM, thermodynamic integration. Resume : L'hydratation des ions divalent [Mg.sup.2+] and [Zn.sup.2+] est etudiee a partir de simulations de dynamique moleculaire et trois approches theoriques de complexite croissante: le champ de force non-polarisable de CHARMM base sur le modele de molecules d'eau TIP3P, le champ de force polarisable Drude base sur le modele de molecules d'eau SWM4-NDP, et une approche QM/MM pour laquelle la sphere de coordination est representee par une methode ab initio de haute precision basee sur la theorie de fonctionelle de densite (PBE/de f2-TZVPP) tandis que les molecules d'eau plus distantes sont decrites part le modele polarisable SWM4-NDP. Les proprietees structurales ainsi que les fonctions de distribution (radiale, angulaire et azimutale) sont calculees et comparees, demontrant un excellent accord entre le champ de force polarisable et l'approche QM/MM. La distance Mg-O moyenne au contact est de 2.11 Å et la distance Zn-O moyenne est de 2.13 Å. Ces resultats sont en excellent accord avec les donnees experimentales obetenu par diffusion des neutrons et EXAFS. La distance Mg-O moyenne au contact obtenue par le champ de force non-polarisable est trop courte de 0.1 Å [Mg.sup.2+] et [Zn.sup.2+] ont tous deux un nombre de coordination de 6 et ont un mode de coordination octaedrique remarquablement similaires, malgre les differences chimiques entre ces ions et le grande difference d'energie libre d'hydration entre ces deux ions (ΔΔ[G.sub.hydr]). Un calcul d'integration thermodynamique permet d'estimer ΔΔ[G.sub.hydr] et de comparer avec la valeur experimentale de -30.1 kcal [mol.sup.-1]. Le modele non-polarisable predit incorrectement que l'ion [Mg.sup.2+] est plus fortement hydrate que [Zn.sup.2+] avec une erreur d'environ 60 kcal [mol.sup.-1]. Un meilleur resultat est obtenu avec le modele Drude polarisable, mais le ΔΔ[G.sub.hydr] est sous-estime a -13.2 kcal [mol.sup.-1]. Enfin, un ΔΔ[G.sub.hydr] de -34.8 kcal [mol.sup.-1]est obtenu avec l'approche QM/MM, en excellent accord avec la valeur experimentale. Ces calculs demontrent que l'ion [Zn.sup.2+] est plus favorablement hydrate que l'ion [Mg.sup.2+] bien que ces deux ions possedent une structure d'hydration tres semblable. Mots-cles : hydratation des ions, [Mg.sup.2+],[Zn.sup.2+], dynamique moleculaire, des champs de force polarisables, QM/MM, l'integration thermodynamique., Introduction The solvation of ions is an enduring fascination of physical, inorganic, and analytical chemists. The interaction between an ion and the solvent is strongly dependent on the properties of [...]

Thermolysin-like proteases (TLPs), a large group of zinc metalloproteases, are synthesized as inactive precursors. TLPs with a long propeptide (~200 residues) undergo maturation following autoprocessing through an elusive molecular mechanism. We report the first two crystal structures for the autoprocessed complexes of a typical TLP, MCP-02. In the autoprocessed complex, Ala205 shifts upward by 33 [Angstrom] from the previously covalently linked residue, His204, indicating that, following autocleavage of the peptide bond between His204 and Ala205, a large conformational change from the zymogen to the autoprocessed complex occurs. The eight N-terminal residues (residues Ala205-Gly212) of the catalytic domain form a new [beta]-strand, nestling into two other [beta]-strands. Simultaneously, the apparent [T.sub.m] of the autoprocessed complex increases 20[degrees]C compared to that of the zymogen. The stepwise degradation of the propeptide begins with two sequential cuttings at Ser49-Val50 and Gly57-Leu58, which lead to the disassembly of the propeptide and the formation of mature MCP-02. Our findings give new insights into the molecular mechanism of TLP maturation. zymogen conversion | zinc metalloproteases inhibition | intrarnolecular chaperone doi/ 10.1073/pnas.1005681107

N-(Thio)phosphorylated (thio)carbamides and (thio)amides are proposed as modifiers of polymer nitrocellulose membranes for the adsorption preconcentration of Ni(II), Zn(II), and Cd(II) from aqueous solutions. The binding constants of metal ions with the immobilized reagents are 1.5--2.5 times higher than those with monomer ligands in solution. The preconcentration coefficients are 1950--3500. A procedure was developed for the adsorption preconcentration and recovery of Ni(II), Zn(II), and Cd(II) as complex compounds, using nitrocellulose membranes modified with N-(thio)phosphorylated thiocarbamides and thioamides. DOI: 10.1134/S1061934810020061, The use of adsorbents modified with chelating agents or functional groups considerably increases the recovery rate and partition coefficients of metal ions. Some cases are known when mono- and polyamine [...]

We have studied the deposition of Zn metal onto a polished gold-coated quartz crystal with in situ tapping-mode atomic force microscopy (AFM), while simultaneously recording chronoamperometric and acoustic impedance quartz crystal microbalance (QCM) measurements. We are able to demonstrate good correlation between the three techniques. Modeling of the chronoamperometric dam recorded for the initial nucleation process of the same experiment suggests that nucleation initially occurred via a progressive mechanism. Crystallites of different sizes were clearly visible from the AFM images throughout the whole deposition time monitored, suggesting that sustained nucleation also occurs via a progressive mechanism. 10.1021/ac901329e

Hydrolysis of Zn is investigated as the second step in a ZnO/Zn redox solar water splitting process. Zinc is evaporated and hydrolyzed with steam in a hot wall flow tubular reactor The influence of the reactor temperature distribution and residence time on hydrogen conversion was measured for furnace set point temperatures of 1023 K and 1073 K. The yield of ZnO aerosol was measured in situ using a scanning differential mobility sizer. The composition and morphology of the solid product were characterized with X-ray diffraction and microscopy. Hydrogen conversions of 87-96% at temperatures above zinc saturation are attributed primarily to hydrolysis of zinc(g) at the wall of the reactor at temperatures from 800 K to 1077 K.

Room-temperature Mossbauer spectra of five specimens of typical, Zn-poor rhodonite and five of Zn-rich rhodonite ('fowlerite') have been obtained to determine whether the spectra reflect structural differences between the two varieties. All Fe is divalent and in the high spin state, and the spectra support the interpretation that Fe is present in al! five M sites. Assignment of Mossbauer doublets to specific sites is made principally on the basis of isomer shift values and relationships between quadrupole splitting and polyhedral distortion parameters determined from previously reported crystal-structure refinements. Trends in Mossbauer parameters show correlations with trends in steric details of the sites, both among individual M sites within Zn-rich and Zn-poor varieties and between corresponding M sites of rhodonite and fowlerite. In particular, the Mossbauer parameters for the geometrically similar M1 and M2 sites are similar, and those of M4 and M5 reflect the tendency of the former toward more tetrahedral character and the latter toward less distortion in fowlerite. Iron occupancy is largely a function of polyhedral volume, although there is a secondary preference for octahedral coordination. Structural differences previously determined between rhodonite and fowlerite, which are driven principally by high concentrations of Zn in M4 and Ca in MS, ate structurally pervasive and are maintained even when Fe substitutes for Zn or Ca. Keywords: Rhodonite, fowlerite, Mossbauer spectroscopy, pyroxenoid

Messenger RNA transcripts are coated from cap to tail with a dynamic combination of RNA binding proteins that process, package, and ultimately regulate the fate of mature transcripts. One class of RNA binding proteins essential for multiple aspects of mRNA metabolism consists of the poly(A) binding proteins. Previous studies have concentrated on the canonical RNA recognition motif-containing poly(A) binding proteins as the sole family of poly(A)-specific RNA binding proteins. In this study, we present evidence for a previously uncharacterized poly(A) recognition motif consisting of tandem CCCH zinc fingers. We have probed the nucleic acid binding properties of a yeast protein, Nab2, that contains this zinc finger motif. Results of this study reveal that the seven tandem CCCH zinc fingers of Nab2 specifically bind to polyadenosine RNA with high affinity. Furthermore, we demonstrate that a human protein, ZC3H14, which contains CCCH zinc fingers homologous to those found in Nab2, also specifically binds polyadenosine RNA. Thus, we propose that these proteins are members of an evolutionarily conserved family of poly(A) RNA binding proteins that recognize poly(A) RNA through a fundamentally different mechanism than previously characterized RNA recognition motif-containing poly(A) binding proteins. CCCH zinc finger | poly(A) binding protein | RNA binding

Fluorescently labeled models of the prion protein that allow prion-prion (PrP-PrP) interactions and metal binding ([Cu.sup.2+] and [Zn.sup.2+]) to be investigated on the molecular level were developed. The results show that PrP-PrP interactions are promoted by addition of [Cu.sup.2+] and [Zn.sup.2+] and glutamine and tryptophan residues also play an important role in PrP-PrP interactions.

Highly efficient (40-70% PL QY) and thermal ultrastable Mn: ZnSe d-dots are synthesized using greener approaches by nucleation-doping strategy. These stable d-dots have features of practical emissive materials, particularly for application with high power, high concentration of emitters, and under tough conditions.

The sensor platform of zinpyr 4 (ZP4) through pyrrole-for-pyridyl substitution is modified and the effects of this variation on both photophysical and metal-binding properties are evaluated. The utility of aniline-based ZP probes for select biological imaging applications are investigated.

A complementary set of conjugated (porphinato)zinc(II)-based chromophores structurally related to [5-(4-dimethylaminophenylethynyl)-15-(5-nitrothienyl)-2-ethynyl)-10,20-bis(3,5-bis(3,3-dimethyl-1-butyloxy)phenyl)porphinato]zinc(II) that features ethynylphenyl-, ethynylthiophenyl-, ethynylthiazolyl-, and ethynylbenzothiazolyl-based electron-donating and -accepting moieties is reported. The results have shown that these neutral dipolar molecules express substantial [[beta].sub.1300] values and have described the design modifications for closely related structures with potential utility in long-wavelength electrooptic applications.

Zinc inverted opals are fabricated by means of electrochemical deposition templated on polystyrene artificial opals grown on indium tin oxide and n-doped substrates. Several differences in the infiltration are observed between samples infilled by linear cyclic voltammetry and square wave pulsating potential approaches, leading to the fabrication of metallic photonic crystals with different topologies on semiconducting substrates.

Asymmetric hetero-Diels-Alder (HDA) reactions of N-sulfinyl dienophiles are described using bis(oxazoline)-copper(II) and -zinc(II) triflates and the cycloadditions with cyclic and acyclic 1,3-dienes are studied. The HDA adducts are transformed into N-protected alpha-amino acid methyl esters, amino esters, amino alcohols, and homoallylic amines.

The synthesis, crystal structure and properties of two dimanganese(II) and tetrazinc(II) discrete assemblies from a rigid organic clip and corresponding metal acetates are presented.

The ligand of N,N'-diethyl-2,3-dihydroxyterephthalamide are characterized in metal complexes with Zn(IV), Ce(IV), Th(IV). In addition, single crystal x-ray diffraction analysis is reported.

Synthesis of phosphonate functionalized ferrocene allowed its subsequent inorganic polymerization with a zinc salt. The crystallographic structure of the compound shows a unique two-dimensional ferrocane arrangement anchored on a one dimensional Zn-O-P-Zn backbone.

The molecular structures of [Ni (H-4)](sub 2) and [Zn (H-4)](sub 4) are determined by X-ray diffraction. The findings indicate distorted tertrahedral coordination geometry for the zinc (II) ions in an NS(sub 3) coordination sphere.

The reaction of nucleobases (adenine or purine) with metallic salt in the presence of potassium oxalate in an aqueous solution yields one-dimensional Oxalato-bridged Cu(II), Co(II), and Zn(II) complexes with nucleobases as terminal ligands. Variable-temperature magnetic susceptibility measurements of the Cu(II) and Co(II) complexes show that occurrence of antiferromagnetic interchain interactions.

Five new dinuclear zinc complexes are synthesized in order to make new structural and functional models for active site of zinc phosphotriesterase. The reactivity of a symmetric Zn2BCIMP complex (BCIMP = 2,6-bis[N-(N-(carboxylmethyl)-N-((1-methylimidazol)-methyl)amine)methyl]-4-methylphenolate) with coordinatively saturated zinc ions are compared to a corresponding asymmetric Zn2ICIMP (ICIMP = 2-(N-isopropyl-N-((1-methylimidazolyl)methyl)aminomethyl)-6-(N-carboxylmethyl-N-((1-methylimidazolyl)methyl)aminomethyl)-4-methylphenol) complex with an available coordination site and the functional studies modeling the hydrolysis of both RNA and DNA are discussed.

The bis (imino) pyridine iron complex, [{2,6-(MeC=N-2,6-Pr2C6H3)2C5H3N}FeCl2], in combination with MAO and ZnEt2(> 500 equiv), is shown to catalyze polyethylene chain growth on zinc. The catalyzed chain growth process is characterized by an exceptionally fast and reversible exchange of the growing polymer chains between the iron and zinc centers.

The structure-property relationships in a series of meso-tetraphenylporphyrins modified by annulations of the pyrrole ring with either benzo or naphtho substituents are studied. Direction of this research includes modification of the structure of the annulated porphyrin by adding various functional groups to the benzo and/or naphtho region for maintaining solubility in the absence of the meso-phenyl groups.

The synthesis of high-quality alloyed Zn(sub x)Cd(sub 1-x)S nanocrystals at high temperatures is accomplished by the reaction of a mixture of CdO-oleic and ZnO-oleic acid complexes with sulfur in the noncoordinating solvent octadecene system. Results indicate that the uniform particle size and shape, high homogeneity in composition, and large ratio of particle radius and exciton Bohr radius (R(sub r/B)) corresponding to the quantum confinement effect (QCE) could be responsible for the highly narrow spectral width.

Bismuth metal, upon activation by zinc fluoride, can effect the crossed aldol reaction between [alpha]-bromocarbonyl compounds and aldehydes in aqueous media. The reaction was found to be regiospecific and syndiastereoselective. Key words: bismuth, zinc fluoride, aldol reaction, regioselectivity, aqueous media.

The assembly kinetics of a membrane protein, the bc1 complex, is investigated using a newly developed continuous-angle laser light scattering technique. The assembly process of the bc1 complex increases both the size of the aggregates and the compactness of the internal structure. The assembly rate is controlled by the presence of zinc as well as by the concentration of PEG, the crystallizing reagent.

The preparation, structural characterization, and detailed lactide polymerization behavior of a new Zn(II) alkoxide complex, (L1ZnOEt)(Sub 2) (L1=2,4-di-tert-butyl-6- {[(2'-dimethylaminoethyl)methylamino]-methyl}phenolate) is reported. The effect of impurities on the molecular weight of the product polymers was accounted for using a simple model.

ZnS-passivated CdS:Mn nanocrystals are synthesized for a yellow emitting nanocrystal phosphor. The different roles of the conjugated polymer and the nanocrystal layers for hole transport and electron transport are discussed.

The synthesis of semiconductor nanocrystals of PbS, ZnS, CdS, and MnS is reported through a facile and inexpensive synthetic process. The synthetic procedure developed, offers several important, advantageous features for the synthesis of sulfide nanocrystals.

A study is conducted to clarify the nature of the zinc phase present in Zn/SiO2 samples not only after calcination, but also after drying. It is found that after drying at 25 or 50 degree C, the supported zinc phase is an amorphous nitrate, whereas after drying at 200 degree C, it is almost already fully transformed into zinc silicate.

Time-resolved polarized pump-probe spectroscopic studies show that the excited states of two meso-to-meso ethyne-bridged bis[(porphinato)zinc(II)] compounds displays a number of unusual spectroscopic and dynamic properties. Both the compounds exhibit significant dynamic in both the Q-state and NIR spectra domains.

A second-generation fluorescent sensor for Zn(super 2) from the Zinpyr family, ZP4 is synthesized and characterized. ZP4 is prepared by a convergent synthesis, where the fluorescein scaffold and the Zn(super 2+) binding fragment are prepared independently and then linked to yield the final sensor.

Density functional methods are utilized to compute pK(sub a) values using a model of the catalytic site of tumor necrosis factor alpha converting enzyme (TACE) and to predict a concomitant mechanism of binding, consistent with lowering the pK(sub a) of the bound ligand and raising the pK(sub a) of the active site Glu-406. The calculations suggest that binding to the zinc ion (Zn(super 2+)) within the binding cavity of TACE lowers the pK(sub a) of hydroxamic and carboxylic acids.

The findings on Lewis acid-catalyzed cyclopropanation of halomethylzinc alkoxides generated from an alcohol and bis(halomethyl)zinc are described. The species can be used as inter-or intra molecular cyclopropanating agents.

The synthesis of zinc blende (InP)ZnCdSe2 core-shell quantum dots (QDs) is reported. The quality of the epitaxially grown shells was monitored by adsorption and emission spectra and transmission electron microscopy (TEM).

Nonlocal DFT provides an excellent description of the structural and conformational properties of metallohydroporphyrins and related complexes. The nickel (II) complexes are found to be strongly ruffled and the zinc (II) complexes planar, consistent with experimental results.

The bis(mercaptoimidazolyl)(pyrazolyl)hydroborato derivatives [pzBm(super Me)](sub 2)Zn, [pzBm(super Me)](sub 2)Co, and [pzBm(super Me)](sub 2)Cd are isolated and structurally characterized by X-ray diffraction. These comparisons state that zinc has a greater preference for tetrahedral M[S4] coordination than does either cobalt or cadmium, an observation that is in accord with the prevalent role of zinc in the structural sites of enzymes.

The coordination chemistry of lead(II) is investigated with three O, S donor ligands: thiomaltol, 3-hydroxy-1-methyl-2(1H)-pyridinethione (3,2-HOPTO), and 3-hydroxy-1,2-dimethyl-4(1H)-pyridinethione (3,4-HOPTO). Further the X-ray structures of [Pb(thiomaltolato)2] and [Pb(3,4-HOPTO)2] are solved, revealing the expected 4-coordinate geometries.

The framework in Zinc(II) coordination polymer is described. Reversible construction of a nonporous framework from a nonporous framework is found in the zinc(II) coordination polymer with 4,4'-oxybis(benzoate) (oba) [Zn2(oba)2(dmf)2], which has 1nm scale channels transforms to the nonporous coordination polymer with the loss of a porous framework.

A nickel-catalyzed synthesis of unsymmetrical aryl sulfides from various aryl iodides and dialkyl- or diaryl-disulfide by the addition of zinc in one-pot is described. Two RS groups in (RS)2 can be used in this system.

A study is conducted to demonstrate that high exposed lead is vulnerable to metal ion displacement on reaction with zinc which results in a regular square pyramidal coordination about zinc within a [N (sub 2)S(sub 2)Zn](sub 2). Analysis of the two monomeric subunits accounted for the stability of the zinc structure over that of the lead.

Pyridine-2,4,6-tricarboxylic acid (ptcH3) reacts with a Zn(II) salt at room temperature to form different products depending upon the presence or absence of pyridine in the reaction mixture. It has been shown that ptcH3 can be broken almost instantaneously at room temperature by Zn(II) ion in the presence of pyridine, the anion present has no role in this reaction and the reaction is driven forward due to high stability of the product.

A structural characterization of the zinc(II) and copper(II) complexes of clioquinol is reported. A ligand to metal stoichiometry of 2:1 is found in both cases, though in the presence of quite different coordination polyhedra, the findings are discussed in the frame of modern approaches to AlzheimerEs disease treatment.