pH- and mol-ratio dependent formation of zinc(II) coordination polymers with iminodiacetic acid: synthesis, spectroscpic, crystal structure and thermal studies

Metal-binding cyclodextrins: Synthesis and complexation with Zn2+ and Ga3+ cations towards antimicrobial applications

Highly resistant bacteria producing metallo-β-lactamases (MBLs) to evade β-lactam antibiotics, constitute a major cause of life-threatening infections world-wide. MBLs exert their hydrolytic action via Zn2+ cations in their active center. Presently, there are no approved drugs to target MBLs and combat the associated antimicrobial resistance (AMR). Towards this issue, we have prepared a family of cyclodextrins substituted with iminodiacetic acid (IDA) on their narrow side, while the wider side is either unmodified or per-2,3-O-methylated. The molecules form strong coordination complexes with Zn2+ or Ga3+ cations in aqueous solution. Free and metal-complexed compounds have been thoroughly characterized regarding structures, pH-dependent ionization states, distribution of species in solution, pKa values and metal-binding constants. At neutral pH the multi-anionic hosts bind up to four Zn2+ or Ga3+ cations. In vitro, 50 μΜ of the compounds achieve complete re-sensitization of MBL-producing Gram-negative clinical bacterial strains resistant to the carbapenems imipenem and meropenem. Moreover, the radioactive complex [67Ga]Ga-β-IDACYD prepared, displays high radiochemical purity, sufficient stability both overtime and in the presence of human plasma apo-transferrin, thus providing an invaluable tool for future biodistribution and pharmacokinetic studies of β-IDACYDin vivo, prerequisites for the development of therapeutic protocols.

Energy-Saving Pathways for Thermoelectric Nanomaterial Synthesis: Hydrothermal/Solvothermal, Microwave-Assisted, Solution-Based, and Powder Processing

The pillars of Green Chemistry necessitate the development of new chemical methodologies and processes that can benefit chemical synthesis in terms of energy efficiency, conservation of resources, product selectivity, operational simplicity and, crucially, health, safety, and environmental impact. Implementation of green principles whenever possible can spur the growth of benign scientific technologies by considering environmental, economical, and societal sustainability in parallel. These principles seem especially important in the context of the manufacture of materials for sustainable energy and environmental applications. In this review, the production of energy conversion materials is taken as an exemplar, by examining the recent growth in the energy-efficient synthesis of thermoelectric nanomaterials for use in devices for thermal energy harvesting. Specifically, "soft chemistry" techniques such as solution-based, solvothermal, microwave-assisted, and mechanochemical (ball-milling) methods as viable and sustainable alternatives to processes performed at high temperature and/or pressure are focused. How some of these new approaches are also considered to thermoelectric materials fabrication can influence the properties and performance of the nanomaterials so-produced and the prospects of developing such techniques further.

Immobilized Metal Affinity Chromatography as a Drug Discovery Platform for Metalloenzyme Inhibitors

Immobilized metal-ion affinity chromatography (IMAC) used to purify recombinant proteins features a resin-bound 1:1 Ni(II)-iminodiacetic acid (IDA) complex. This hemi-saturated Ni(II)-IDA system containing exchangeable sites at the metal ion is re-cast as a surrogate of a coordinatively-unsaturated metalloenzyme active site, with utility for selecting compounds with metal-binding groups from mixtures as potential metalloenzyme inhibitors. Exchanging Ni(II) for other metal ions could broaden the scope of metalloenzyme target. This work examined the performance of Cu(II)-, Fe(III)-, Ga(III)-, Ni(II)-, or Zn(II)-IMAC resins to reversibly bind experimental or clinical metalloenzyme inhibitors of Zn(II)-ACE1, Zn(II)-HDAC, Fe(II)/(III)-5-LO or Cu(II)-tyrosinase from a curated mixture (1-17). Each IMAC system gave a distinct selection profile. The Zn(II)-IMAC system selectively bound the thiol-containing Zn(II)-ACE1 inhibitors captopril and omapatrilat, and the Fe(III)-IMAC system selectively bound the Fe(II)/(III)-5-LO inhibitor licofelone, demonstrating a remarkable IMAC-metalloenzyme metal ion match. IMAC provides a simple, water-compatible platform, which could accelerate metalloenzyme inhibitor discovery.

Iminodiacetic Acid as a Novel Metal-Binding Pharmacophore for New Delhi Metallo-β-lactamase Inhibitor Development

The fungal natural product aspergillomarasmine A (AMA) has been identified as a noncompetitive inhibitor of New Delhi metallo-β-lactamase-1 (NDM-1) that inhibits by removing ZnII from the active-site. The nonselective metal-chelating properties and difficult synthesis and derivatization of AMA have hindered the development of this scaffold into a potent and selective inhibitor of NDM-1. Iminodiacetic acid (IDA) has been identified as the metal-binding pharmacophore (MBP) core of AMA that can be leveraged for inhibitor development. Herein, we report the use of IDA for fragment-based drug discovery (FBDD) of NDM-1 inhibitors. IDA (IC50 =120 μM) was developed into inhibitor 23 f (IC50 =8.6 μM, Ki =2.6 μM), which formed a ternary complex with NDM-1, as evidenced by protein thermal-shift and native-state electrospray ionization mass spectrometry (ESI-MS) experiments. Combining mechanistic analysis with inhibitor derivatization, the use of IDA as an alternative AMA scaffold for NDM-1 inhibitor development is detailed.

Amino Acid-Derived Sensors for Specific Zn2+ Detection Using Hyperpolarized 13 C Magnetic Resonance Spectroscopy

Alterations in Zn2+ concentration are seen in normal tissues and in disease states, and for this reason imaging of Zn2+ is an area of active investigation. Herein, enriched [1-13 C]cysteine and [1-13 C2 ]iminodiacetic acid were developed as Zn2+ -specific imaging probes using hyperpolarized 13 C magnetic resonance spectroscopy. [1-13 C]cysteine was used to accurately quantify Zn2+ in complex biological mixtures. These sensors can be employed to detect Zn2+ via imaging mechanisms including changes in 13 C chemical shift, resonance linewidth, or T1 .

Crystal structure of a heterometallic coordination polymer: catena-poly[[[tetra-aqua-cobalt(II)]-μ-pyridine-2,6-di-carboxyl-ato-calcium(II)-μ-pyridine-2,6-di-carboxyl-ato] dihydrate]

In the crystal of the title polymeric complex, {[CoCa(C7H3NO4)2(H2O)4]·2H2O} n (1), the CoII ion is N,O,O'-chelated by two pyridine-2,6-di-carboxyl-ate anions in a distorted N2O4 octa-hedral geometry, and two carboxyl-ate O atoms of pyridine-2,6-di-carboxyl-ate anions bridge tetra-aqua-calcium(II) units to form polymeric chains propagating along the b-axis direction. In the crystal, O-H⋯O and C-H⋯O hydrogen bonds, and offset π-π stacking inter-actions [inter-centroid distances = 3.551 (1) and 3.746 (1) Å] involving inversion-related pyridine rings link the polymeric chains and lattice water mol-ecules to form a supra-molecular three-dimensional framework.

A novel hexanuclear titanium(iv)-oxo-iminodiacetate cluster with a Ti6O9 core: single-crystal structure and photocatalytic activities

A new family of hexanuclear titanium(iv)-oxo-carboxylate cluster K7H[Ti6O9(ida)6]Cl2·13H2O {Ti6O9} has been synthesized via the H2O2-assisted reaction between TiCl4 and iminodiacetate ligands. This cluster was fully characterized by single-crystal X-ray diffraction and a wide range of analytical methods, including FT-IR, UV/vis spectroscopy as well as electrochemistry and thermogravimetric analysis. As a new type of carboxylate substituted Ti-oxo-cluster, the structural motif of the {Ti6O9} cluster consists of one symmetric {Ti6O6} hexagonal prism with two staggered triangular {Ti3O3} subunits linked by three μ2-O bridges. The {Ti6O9} polyanions are linked by K(+) cations to form a novel 3D architecture. The structural information and stability of the {Ti6O9} polyanion in aqueous solution were thoroughly investigated by solid-state/solution NMR, ESI-MS spectroscopy. Moreover, this Ti-oxo cluster exhibits remarkable potential as a visible-light homogeneous photocatalyst for degradation of rhodamine B (RhB). Finally, a proposed peroxotitanium(iv)-mediated photocatalytic pathway involved is illustrated by spectroscopic data.

An asymmetric binuclear zinc(ii) complex with mixed iminodiacetate and phenanthroline ligands: synthesis, characterization, structural conversion and anticancer properties

A water-soluble asymmetric binuclear zinc(ii) complex with mixed iminodiacetate and 1,10-phenanthroline ligands exhibited promising anticancer activity and low toxicity, suggesting potential as a chemotherapeutic agent.

Characterization of a nitrilase from Arthrobacter aurescens CYC705 for synthesis of iminodiacetic acid

A nitrilase gene cyc705 from Arthrobacter aurescens CYC705 for synthesis of iminodiacetic acid (IDA) was cloned. This gene contained a 930 bp ORF, which encoded a polypeptide of 310 amino acids. A recombinant Escherichia coli BL21(DE3)/pET28a-cyc705 was constructed to achieve the heterologous expression of cyc705. This recombinant nitrilase was purified to homogeneity with a molecular weight of 36.7 kDa on SDS-PAGE and mass spectrometry, and characterized to be an oligomer of 14 subunits by gel permeation chromatography. Using iminodiacetonitrile (IDAN) as the substrate, the Vmax, Km, kcat and kcat/Km were 9.05 U mg(-1), 43.17 mM(-1), 94.1 min(-1) and 2.18×10(3) min(-1) M(-1), respectively. The optimum temperature and pH were 25°C and 5.8. The suitable substrates for the purified nitrilase were short-chain aliphatic dinitriles. High concentration of IDAN could be hydrolyzed to IDA in a shorter time.

Solvent-directed Structure Variation from Mononuclear to Bis-methoxo-bridged Binuclear Copper (II) Compound: Crystal Structures and Proton-conduction

In ethanol, the reaction of 2-(methylthio)-4-(pyridin-2-yl)pyrimidine) with Cu(NO3)2 (2-MTPP) yielded a mononuclear Cu(II) coordination compound [(C10H9N3S)2CuNO3]NO3.H2O. In contrast, a discrete bis-methoxo-bridged binuclear Cu(II) coordination compound resulted when ethanol was substituted by methanol. [(C10 H9 N3S)2CuNO3]NO3.H2O and [(C10 H9 N3S)(CH3O) CuNO3]2 have been structurally investigated by single crystal X-ray diffraction. In [(C10H9N3S)2CuNO3]NO3.H2O, uncoordinated nitrate anions and water guest molecules form an interesting one-dimensional hydrogen-bonded chain that is accommodated into an open rhomboidal channel constructed by [Cu(NO3)(2-MTPP)2]+ cations. In [(C10H9N3S)(CH3O)CuNO3]2, binuclear molecules are arrayed in a linear fashion via C–H…O hydrogen bonding interactions. Moreover, [(C10H9N3S)2CuNO3]NO3.H2O has a proton-conductive property with a room-temperature conductivity of 4.96×10−8 S cm−1.