Switching from 4+1 to 4+2 zinc coordination number through the methyl group position on the pyridyl ligand in the geometric isomers bis[N-2-(4/6-methyl-pyridyl)salicylaldiminato-κ2N,O]zinc(II)

Metal induced non-metallothionein protein in earthworm: A new pathway for cadmium detoxification in chloragogenous tissue

Earthworms neutralize toxic metals by a small (∼13 kDa) cysteine rich metal binding protein, metallothionein (MT). Although the rate of metal accumulation and MT expression does not correlate well, the reason behind such inconsistency has not yet been deciphered. The present investigation clearly demonstrates that expression of some non-MT metal induced proteins is responsible for such incongruity. Applying selective protein isolation techniques in fluorescence tagged cadmium exposed (135 mg/kg) earthworms we were able to purify a 150 kDa metal induced protein (MIP) among others. After 60 days of exposure cadmium accumulation in earthworm intestines was significant. Immunofluorescence staining followed by confocal microscopy exhibited that MIP accumulates ingested cadmium in the intestinal region and eventually deposits the metal in the chloragogenous tissue. We determined the N-terminal sequence of 15 amino acid residues and after bioinformatics analysis, it was concluded that MIP is most probably a glutamic acid rich, novel cadmium binding protein. To further validate the binding mechanism, we conducted paper chromatography and continuous variation experiments which evidenced that cadmium readily binds to glutamic acid. The present finding is the first in-vivo evidence of a non-metallothionein cadmium binding protein induced in the intestines of earthworm exposed to a cadmium rich environment.

Schiff base ligands derived from 1,2-bis(2′-nitro-/amino-phenoxy)-3-R-benzene and 2-hydroxy-1-naphthaldehyde and their Cu/Zn(ii) complexes: synthesis, characterization, X-ray structures and computational studies

Racemic crystals of Cu/Zn(ii)-tetradentate Schiff base ligands with Λ/Δ-chirality induction at-metal center.

Zinc(II) complexes with aromatic nitrogen-containing heterocycles as antifungal agents: Synergistic activity with clinically used drug nystatin

Three novel Zn(II) complexes, [ZnCl₂(qz)₂] (1), [ZnCl₂(1,5-naph)]_n (2) and [ZnCl₂(4,7-phen)₂] (3), where qz is quinazoline, 1,5-naph is 1,5-naphthyridine and 4,7-phen is 4,7-phenanthroline, were synthesized by the reactions of ZnCl₂ and the corresponding N-heterocyclic ligand in 1:2 molar ratio in ethanol at ambient temperature. The characterization of these complexes was done by NMR, IR and UV-Vis spectroscopy, and their crystal structures were determined by single-crystal X-ray diffraction analysis. Complexes 1 and 3 are mononuclear species, in which Zn(II) ion is tetrahedrally coordinated by two nitrogen atoms belonging to two qz or 4,7-phen ligands, respectively, and by two chloride anions, while complex 2 is a 1D coordination polymer that contains 1,5-naph as bridging ligand between two metal ions. In agar disc-diffusion assay, complexes 1-3 manifested good inhibitory activity against two investigated Candida strains (C. albicans and C. parapsilosis), while not inducing toxic effects on the healthy human fibroblast cell line (MRC-5). This activity was not fungicidal, as revealed by the broth microdilution assay, however complex 3 showed the ability to modulate Candida hyphae formation, which is an important process during infection and showed significant synergistic effect with clinically used antifungal polyene nystatin.

Spontaneous resolution of a Δ/Λ-chiral-at-metal pseudo-tetrahedral Schiff-base zinc complex to a racemic conglomerate with C–H⋯O organized 41- and 43-helices

Weak supramolecular interactions can be decisive!

Determination of trace metal concentration in compost, DAP, and TSP fertilizers by neutron activation analysis (NAA) and insights from density functional theory calculations

Leaching of toxic metals from fertilizers is a growing concern in an agricultural country like Bangladesh due to the serious consequences in health and food chain. Fertilizers used in farming fields and nurseries (plant sales outlet) in the mid-southern part of Bangladesh were collected for the determination of toxic metals. This study employed the neutron activation method and a relative standardization approach. Three standard/certified reference materials, namely NIST coal fly ash 1633b, IAEA-Soil-7, and IAEA-SL-1 (lake sediment), were considered for elemental quantification. Concentration of As (2.63-16.73 mg/kg), Cr (40.93-261.77 mg/kg), Sb (0.47-63.58 mg/kg), Th (1.44-19.16 mg/kg), and U (1.90-209.41 mg/kg) were determined in fertilizers. High concentrations of Cr, Sb, and U were detected in some compost and phosphate fertilizers (TSP and diammonium phosphate (DAP)) in comparison with the IAEA/European market standard and other studies. Quantum mechanical calculations were performed to understand the molecular level interaction of CrO₃, Sb₂O₃, and AsO₃, with DAP by employing density functional theory with the B3LYP/SDD level of theory. Our results indicated that CrO₃ and Sb₂O₃ have strong binding affinity with DAP compared to AsO₃, which supports the experimental results. These compounds attached to the phosphate group through covalent-like bonding with oxygen. The frontier molecular orbital calculation indicated that HOMO-LUMO gap of the AsO₃-DAP (5.46 eV) and Sb₂O₃-DAP (6.48 eV) complexes are relatively lower than the CrO₃-DAP, which indicates that As and Sb oxides are chemically more prone to attach with the phosphate group of DAP fertilizer.

Exploring metal detoxification and accumulation potential during vermicomposting of Tea factory coal ash: sequential extraction and fluorescence probe analysis

Metal contamination from coal ashes (CAs) is widely recognized as a significant environmental concern. To learn more about metal detoxification and accumulation potential of earthworm species, metal-rich tea factory coal ashes (TFCA) were fed to Eisenia fetida and Lampito mauritii by employing a fluorescent tag detection method. Fascinatingly, on feeding fluorescence probed Zn and Cd along with cow dung to Eisenia fetida, the detection of the gut-proteins with a molecular mass higher than 100 kDa was a distinct evidence of metal binding. Significant increases were observed in the content of humified organic C [humic acid (HAC) and fulvic acid C (FAC)] and degree of humification during vermicomposting. Concurrently, considerably large amount of toxic metals (Cr, Cd, Pb, and Zn) was transformed from exchangeable to recalcitrant (organic matter and mineral bound) fractions. Moreover, total metal concentrations were reduced with high removal efficiency upon vermicomposting.

Chirality at metal and helical ligand folding in optical isomers of chiral bis(naphthaldiminato)nickel(ii) complexes

Ni-Schiff base complexes combine ligand chirality, chirality at metal, and helical ligand folding in a concerted way.