Crystal structure and Hirshfeld surface analysis of {2-[bis-(pyridin-2-ylmeth-yl)amino]-ethane-1-thiol-ato}-chlorido-cadmium(II).

The title compound, [Cd(CHNS)Cl] or [CdCl] (), where = 2-[bis-(pyridin-2-ylmeth-yl)amino]-ethane-1-thiol, was prepared and structurally characterized. The Cd complex crystallizes in 2/ with a distorted trigonal-bipyramidal metal coordination geometry. Supra-molecular inter-actions in include parallel offset face-to-face inter-actions between inversion-related pyridyl rings and potential hydrogen bonds with chlorine or sulfur as the acceptor.

Homo- and Heteronuclear Group 12 Metallothionein Type B Cluster Analogs: Synthesis, Structure, H NMR and ESI-MS.

Metallothioneins (MTs) are a ubiquitous class of small cysteine-rich metal-binding proteins involved in metal homeostasis and detoxification with highly versatile metal binding properties. Despite the long-standing association of MT with MS and MS metal clusters, synthetic complexes with these core architectures are exceptionally rare. Here, we demonstrate an approach to synthesizing and characterizing aggregates of group 12 metal ions with monocyclic MS cores in acetonitrile solution without the protection of a protein.

Radical Complexes of Nickel(II)/Copper(II) and Redox Non-innocent MB-DIPY Ligands: Unusual Stability and Strong Near-Infrared Absorption at λ ∼1300 nm.

The preparation of radicals with intense and redox-switchable absorption beyond 1000 nm is a long-standing challenge in the chemistry of functional dyes. Here we report the preparation of a series of unprecedented stable neutral nickel(II) and copper(II) complexes of "Manitoba dipyrromethenes" (MB-DIPYs) in which the organic chromophore is present in the radical-anion state. The new stable radicals have an intense absorption at λ ∼1300 nm and can be either oxidized to regular [M (MB-DIPY)] (M=Cu or Ni) or reduced to [M (MB-DIPY)] compounds.

HYSCORE Insights into the Distribution of the Unpaired Spin Density in an Engineered Cu Site in Azurin and Its His120Gly Variant.

A comparative study of the H and N hyperfine interactions between the Cu site in an engineered Cu center in azurin (WT-CuAz) and its His120Gly variant (H120G-CuAz) using the two-dimensional ESEEM technique, HYSCORE, is reported. HYSCORE spectroscopy has clarified conflicting results in previous electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) studies and found clear differences between the two Cu azurins. Specifically, a hyperfine coupling A of 15.

Nitrite Reductase Activity in Engineered Azurin Variants.

Nitrite reductase (NiR) activity was examined in a series of dicopper P.a. azurin variants in which a surface binding copper site was added through site-directed mutagenesis.

Mercury metallation of the copper protein azurin and structural insight into possible heavy metal reactivity.

Mercury(II) metallation of Pseudomonas aeruginosa azurin has been characterized structurally and biochemically. The X-ray crystal structure at 1.5Å of mercury(II) metallated azurin confirms the coordination of mercury at the copper binding active site and a second surface site.

Structure and isomerization comparison of Zn(II), Cd(II) and Hg(II) perchlorate complexes of 2,6-bis([(2-pyridyl-methyl)amino]methyl)pyridine.

The divalent zinc triad perchlorate coordination chemistry of 2,6-bis([(2-pyridyl-methyl)amino]methyl)pyridine (L) was investigated by X-ray crystallography and solution state (1)H NMR. New complexes [HgL(ClO4)2] (1) and [CdL(ClO4)2] (2) were isolated as bicapped distorted square pyramidal racemates, contrasting with the approximate trigonal bipyramidal structure of [ZnL](ClO4)2 (3). Although rapid inter- and intramolecular exchange is common for simple complexes of zinc triad metal ions, conditions for slow intramolecular isomerization on both the δ and J(HH) time scales were established for 1, 2 and 3.

Isomorphic deactivation of a Pseudomonas aeruginosa oxidoreductase: The crystal structure of Ag(I) metallated azurin at 1.7 Å.

Multiple biophysical methods demonstrate that silver effectively metallates Pseudomonas aeruginosa apo-azurin in solution. X-ray crystallography of the silver-modified protein reveals that silver binds to azurin at the traditional copper mediated active site with nearly identical geometry. Cyclic voltammetry indicates that the silver adduct is redox inert.

Stereoselective synthesis of pyroglutamate natural product analogs from α- aminoacids and their anti-cancer evaluation.

Alkylation of α-amino acid derived iminoesters with Baylis-Hillman (BH) reaction template based allyl bromides/allyl acetates followed by acidic hydrolysis furnished α-methylene-β-substituted-pyroglutamates and α-alkylidene pyroglutamates respectively. Application of these methodologies has been demonstrated in the synthesis of fused [3.2.

Carbonate-templated self-assembly of an alkylthiolate-bridged cadmium macrocycle.

In the presence of Cd(ClO4)2 and a base, a new mixed N,S-donor alkylthiolate ligand supported both carbonate formation from atmospheric CO2 and the self-assembly of a novel bicapped puckered (CdS)6 molecular wheel. The remarkable stability of the complex was demonstrated by slow intermolecular ligand exchange on the (2)J(HH) and J((111/113)Cd(1)H) time scales at elevated temperature. Both CO2 and the base were required to convert amorphous "CdLClO4" precipitated in the absence of air to the carbonate complex.

Reduction potential variations in azurin through secondary coordination sphere phenylalanine incorporations.

Recent evidence has shown that the properties of metal binding sites can be tuned by more than the ligands in the primary coordination sphere. We investigated the incorporation of four phenylalanine residues into the secondary coordination sphere of the small soluble blue copper protein azurin. The locations for placement of these residues in azurin were based on the structure of the highly hydrophobic blue copper protein rusticyanin, which is known to have a significantly higher reduction potential than azurin.

A synthetic model of Hg(II) sequestration.

Tridentate ligand N-(2-pyridylmethyl)-N-(2-(ethylthiolato)amine (L) forms the novel complex [Hg(5)(L)(6)](ClO(4))(4).toluene () with a bicyclo[3.3.

9-O-Ethyl-berberrubinium iodide monohydrate.

9-eth-oxy-10-meth-oxy-5,6-dihydro-1,3-dioxolo[4,5-g]isoquinolino-[3,2-a]isoquin-olin-7-ium iodide monohydrate), 2C(21)H(20)NO(4) (+)·2I(-)·H(2)O, two independent mol-ecules pack in the unit cell, where interactions between the molecules are stabilized by weak inter-molecular π-π stacking inter-actions [centroid-centroid distances in the range 3.571 (4) to 3.815 (4)Å].

Structural and NMR characterization of Sm(III), Eu(III), and Yb(III) complexes of an amide based polydentate ligand exhibiting paramagnetic chemical exchange saturation transfer abilities.

Complexes of Sm(III), Eu(III), and Yb(III) with a new polydentate ether ligand with amide arms were synthesized. Solid state X-ray structures of the complexes reveal all three complexes crystallize in monoclinic unit cells. The mononuclear complexes have nine coordinate tricapped trigonal prismatic geometries with coordination of all four amide carbonyl oxygen and all three of the backbone ether oxygen atoms.

Bis-tridentate Chelates of an Asymmetric Ligand: X-ray Structures and Solution NMR Characterization of Divalent Zinc Triad Metal Ion Complexes of N-(2-pyridylmethyl)-N-(2-(methylthio)ethyl)amine.

Divalent zinc triad metal ion complexes of type M(L)(2)(ClO(4))(2) (L = N-(2-pyridylmethyl)-N-(2-(methylthio)ethyl)amine) with N(4)S(2) metal coordination spheres were isolated and characterized by X-ray crystallography and variable temperature proton NMR. Although bis-tridentate chelates have nine geometric isomers, the crystallographically characterized complexes of all three metal ions had trans facial octahedral coordination geometry with C(i) symmetry. Despite the low coordination number and geometric preferences of d(10) metal ions, which facilitate inter- and intramolecular exchange processes, dilute solutions of these bis-tridentate chelates exhibited slow geometric isomerization.

Models of noncoupled dinuclear copper centers in azurin.

The successful modeling of metalloproteins is an important step in understanding their structure and function. Toward this goal, models of the noncoupled copper centers found in the enzymes peptidyl alpha-hydroxylating monooxygenase (PHM), dopamine beta-monooxygenase (DBM), and nitrite reductase (NiR) were designed into the small soluble protein azurin. The models are significant because they maintain the existing type 1 (T1) copper, electron transfer site of azurin while including the second designed type 2 (T2) copper center that mimics the T2 catalytic sites in the target enzymes.

Reduction potential tuning of the blue copper center in Pseudomonas aeruginosa azurin by the axial methionine as probed by unnatural amino acids.

The conserved axial ligand methionine 121 from Pseudomonas aeruginosa azurin (Az) has been replaced by isostructural unnatural amino acid analogues, oxomethionine (OxM), difluoromethionine (DFM), trifluoromethionine (TFM), selenomethionine (SeM), and norleucine (Nle) using expressed protein ligation. The replacements resulted in < 6 nm shifts in the S(Cys)-Cu charge transfer (CT) band in the electronic absorption spectra and < 8 gauss changes in the copper hyperfine coupling constants (AII) in the X-band electron paramagnetic resonance spectra, suggesting that isostructural replacement of Met resulted in minimal structural perturbation of the copper center. The slight blue shifts of the CT band follow the trend of stronger electronegativity of the ligands.

Investigation of group 12 metal complexes with a tridentate SNS ligand by X-ray crystallography and 1H NMR spectroscopy.

Two series of zinc triad complexes containing the ligand 2,6-bis(methylthiomethyl)pyridine (L1) were synthesized and characterized by X-ray crystallography and solution-state 1H NMR spectroscopy. The distorted meridional octahedral M(L1)2(ClO4)2 series includes the first structurally characterized Zn(II) and Cd(II) complexes with N2(SR2)4 coordination spheres. Coordination of HgCl2 and ZnCl2 with 1 equiv of ligand afforded mononuclear, five-coordinate species Hg(L1)Cl2 and Zn(L1)Cl2, respectively, with distorted square-pyramidal and trigonal-bipyramidal geometries.

Axial methionine has much less influence on reduction potentials in a CuA center than in a blue copper center.

The role of the highly conserved axial methionine of the purple CuA center in an engineered CuA azurin on modulating the reduction potentials of the copper center was investigated by a systematic replacement of the methionine with glutamate, aspartate, and leucine. In contrast to the same substitutions in the structurally related blue copper azurin, much smaller changes in reduction potential were observed in the CuA azurin upon replacing the methionine ligand with negatively charged Glu (-8 mV) and Asp (-5 mV) and more hydrophobic Leu (+16 mV). These findings are important in understanding the different roles of the two cupredoxins.

Solid-state and solution-state coordination chemistry of the zinc triad with the mixed N,S donor ligand bis(2-methylpyridyl) sulfide.

The binding of group 12 metal ions to bis(2-methylpyridyl) sulfide (1) was investigated by X-ray crystallography and NMR. Seven structures of the chloride and perchlorate salts of Hg(II), Cd(II), and Zn(II) with 1 are reported. Hg(1)(2)(ClO(4))(2), Cd(1)(2)(ClO(4))(2), and Zn(1)(2)(ClO(4))(2).

The selenocysteine-substituted blue copper center: spectroscopic investigations of Cys112SeCys Pseudomonas aeruginosa azurin.

Azurin is a small electron-transfer protein belonging to the cupredoxin family. The Cu atom is located within a trigonal plane coordinated by two histidines (His46 and His117) and a cysteine (Cys112) with two more distant ligands (Gly45 and Met121) providing axial interactions. A Cys112SeCys derivative has been prepared by expressed protein ligation, and detailed UV/vis, EPR and EXAFS studies at the Cu and Se K-edges have been carried out.

Probing the role of axial methionine in the blue copper center of azurin with unnatural amino acids.

Expressed protein ligation was used to replace the axial methionine of the blue copper protein azurin from Pseudomonas aeruginosa with unnatural amino acids. The highly conserved methionine121 residue was replaced with the isostructural amino acids norleucine (Nle) and selenomethionine (SeM). The UV-visible absorption, X- and Q-band EPR, and Cu EXAFS spectra of the variants are slightly perturbed from WT.

Role of the coordinating histidine in altering the mixed valency of Cu(A): an electron nuclear double resonance-electron paramagnetic resonance investigation.

The binuclear Cu(A) site engineered into Pseudomonas aeruginosa azurin has provided a Cu(A)-azurin with a well-defined crystal structure and a CuSSCu core having two equatorial histidine ligands, His120 and His46. The mutations His120Asn and His120Gly were made at the equatorial His120 ligand to understand the histidine-related modulation to Cu(A), notably to the valence delocalization over the CuSSCu core. For these His120 mutants Q-band electron nuclear double resonance (ENDOR) and multifrequency electron paramagnetic resonance (EPR) (X, C, and S-band), all carried out under comparable cryogenic conditions, have provided markedly different electronic measures of the mutation-induced change.