Hybrid Bis-Histidine Phenanthroline-Based Ligands to Lessen Aβ-Bound Cu ROS Production: An Illustration of Cu(I) Significance

We here report the synthesis of three new hybrid ligands built around the phenanthroline scaffold and encompassing two histidine-like moieties: phenHH, phenHGH and H’phenH’, where H correspond to histidine and H’ to histamine. These ligands were designed to capture Cu(I/II) from the amyloid-β peptide and to prevent the formation of reactive oxygen species produced by amyloid-β bound copper in presence of physiological reductant (e.g., ascorbate) and dioxygen. The amyloid-β peptide is a well-known key player in Alzheimer’s disease, a debilitating and devasting neurological disorder the mankind has to fight against. The Cu-Aβ complex does participate in the oxidative stress observed in the disease, due to the redox ability of the Cu(I/II) ions. The complete characterization of the copper complexes made with phenHH, phenHGH and H’phenH’ is reported, along with the ability of ligands to remove Cu from Aβ, and to prevent the formation of reactive oxygen species catalyzed by Cu and Cu-Aβ, including in presence of zinc, the second metal ions important in the etiology of Alzheimer’s disease. The importance of the reduced state of copper, Cu(I), in the prevention and arrest of ROS is mechanistically described with the help of cyclic voltammetry experiments.

Enantioselective C–H Alkylation of N-Arylbenzamides with Vinyl Ethers Catalyzed by an Iridium/Chiral Phosphoramidite–Olefin Complex

Chiral phosphoramidite−olefin hybrid ligands were found to be effective in the iridium-catalyzed asymmetric alkylation of N-arylbenzamides with vinyl ethers. The reaction was catalyzed by a hydroxoiridium catalyst coordinated with the hybrid ligand to give the corresponding products in high yields with high branch- and enantioselectivity.

Determination of Hybrid TSPO Ligands with Minimal Impact of SNP (rs6971) through Molecular Docking and MD Simulation Study

Background: In an endeavor to ascertain high affinity TSPO ligands with minimal single nucleotide polymorphism (SNP), six hybrid molecules have been identified as new leads for future inflammation PET imaging. Objective: Genesis for chemical design was encouraged from structural families of well-known ligands FEBMP and PBR28/ DAA1106 that has demonstrated remarkable TSPO binding characteristics. Methods: All proposed hybrid ligands 1-6 are subjected to molecular docking and simulation studies with wild and mutant protein to study their interactions, binding, consistency of active conformations and are correlated with well-established TSPO ligands. Results: Each hybrid ligand demonstrate better docking score > -11.00 kcal/mol with TSPO with respect to gold standard PK11195 i.e., -11.00 kcal/mol for 4UC3 and -12.94 kcal/mol for 4UC1. On comparison with FEBMP and GE-180 (-12.57,-7.24 kcal/mol for 4UC3 and -14.10,-11.32 kcal/mol for 4UC1), ligand 3 demonstrate maximum docking energy (>-15.50 kcal/mol), minimum SNP (0.26 kcal/mol). Discussion: Presence of strong hydrogen bond Arg148-3.27Å (4UC1) and Trp50-2.43Å, Asp28-2.57Å (4UC3) apart from short-range interactions including π–π interactions with the aromatic residues such as (Trp39, Phe46, Trp135) and (Trp39, Trp108) that attributes towards its strong binding. Conclusion: Utilizing the results of binding energy, we concluded stable complex formation of these hybrid ligands that could bind to TSPO with least effect of SNP with similar interactions to known ligands. Overall ligand 3 stand out as the best ligand having insignificant deviations per residue of protein that can be further explored and assessed in detail for future inflammation PET application after subsequent detailed biological evaluation.

Identification of novel thiadiazin derivatives as potentially selective inhibitors towards trypanothione reductase from Trypanosoma cruzi by molecular docking using the numerical index poses ratio Pr and the binding mode analysis

Chagas disease is a serious health problem in Central and South America for which effective treatment is not currently available. This illness is caused by the protozoa Trypanosoma cruzi, a species that relies on a thiol-based metabolism to regulate oxidative stress. Trypanothione reductase enzyme plays a central role in the metabolic pathway of the parasite. In this work, a virtual screening of a library of novel thiadiazine derivatives against trypanothione reductase using molecular docking was performed. Four different series of hybrid ligands having in the structure one or two peptoid moieties (series I and II) or the tetrazole ring (series III and IV) were considered. An ad hoc numerical index called poses ratio was introduced to interpret the results of the docking analysis and to establish relevant structure-interaction relationships. In addition, six binding modes were found for the ligands with the highest populated conformational clusters after applying contact-based analysis. The most regular and relevant were binding modes I and II, found mainly for ligands from series I. A subsequent molecular docking on human glutathione reductase enzyme allowed to assess the possible cytotoxicity of the ligands towards human cells. A selective binding profile was found for ligands with interactions in the Hydrophobic cleft, the spermidine and the Z subsites inside the active site of trypanothione reductase. At the end of the study, new thiadiazine-based compounds were identified as plausible candidates to selectively inhibit the parasitic enzyme. Graphic abstract

Fluorescent palladium(II) and platinum(II) NHC/1,2,3-triazole complexes: antiproliferative activity and selectivity against cancer cells

Fluorescent Pd(II) and Pt(II) complexes bearing 4-methylene-7-methoxycoumarin (MMC) and 2,6-diispropylphenyl (Dipp) substituted NHC/1,2,3-triazole hybrid ligands are described. Depending on the reaction conditions two different ligand coordination modes are observed, i.e.,...

Complexes of Th(iv) with neutral O–N–N–O hybrid ligands: a thermodynamic and crystallographic study

Thermodynamics of the Th(iv) complexes with two tetradentate ligands bearing hybrid N- and O-donors in CH3OH/10%(v)H2O solutions were determined at 25 °C.