Nickel(II) and Copper(II) complexes of sulphamide and ethylenediamine

Summary The following ethylenediamine(sulphamide)nickel(II) and ethylenediamine(sulphamide)copper(II) complexes were prepared: Ni(en)₃(H₂Su)Cl₂, in which H₂Su is not coordinated; Ni(en)₂(H₂Su)Cl₂ , Ni(en)₂(HSu)Cl · EtOH, Ni(en)₂(HSu)₂,Ni(en)₂(HSu)₂(H₂Su)₂ · EtOH, Cu(en)₂(HSu)₂(H₂Su) · O.5EtOH, in which the sulphamide molecule, H₂Su, or the sulphamidato anion [HSu] are totally or partially coordinated. The comparison of the i.r. spectra of these complexes with those of H₂ Su and NaHSu and with those of the M(en)₂Cl₂ complexes permits the isolation of the sulphamide or sulphamidato (SO₂) and (SN₂) bands which show oxygen-coordination of these ligands to the metal. Some (MO) bands were identified in the far i.r. region.     

Unexpected behaviour of the oxidizing agent sodium m-nitrobenzenesulfonate: Synthesis of a new class of 5-hydroxy benzopyrano-[4,3-c]pyridazin-3(2H)-ones

Sodium m-nitrobenzene sulfonate, widely used in dehydrogenation of 4,5-dihydro-3(2H)-pyridazinones to their corresponding aromatic derivatives, behaves in an unexpected way when 4,4a-dihydro-5H[1]benzopyrano[4,3-c]pyridazin-3(2H)-ones are employed as substrate. The synthesis of a new class of 5-hydroxy[1]benzopyrano[4,3-c]pyridazin-3(2H)-ones is described.     

Synthesis,characterization, crystal structure and antiproliferative in vitro activity of long-chain aliphatic thiosemicarbazones and their Ni(II) complexes

In the course of a research on metal-based compounds active on white blood cell cancers (leukemia, lymphoma and myeloma) nine aliphatic thiosemicarbazones and their nickel complexes have been synthesized with the aim to test their effect on histiocytic lymphoma U937 cell proliferation. All compounds were characterized by elemental, IR and NMR spectra analyses and for five of the complexes also by X-ray crystallography diffraction analysis. Heptanal thiosemicarbazone and the corresponding nickel complex were chosen after a solubility/stability test to carry out preliminary experiments in vitro on human leukemia cell line U937. The complex possesses a remarkable biological activity in inhibiting cell growth and in inducing apoptosis.     

The Binding Pocket at the Interface of Multimeric Telomere G-quadruplexes: Myth or Reality?

Human telomeric DNA with hundreds of repeats of the 5’-TTAGGG-3’ motif plays a crucial role in several biological processes. It folds into G-quadruplex (G4) structures and features a pocket at the interface of two contiguous G4 blocks. Up to now no structural NMR and crystallographic data are available for ligands interacting with contiguous G4s. Naphthalene diimide monomers and dyads were investigated as ligands of a dimeric G4 of human telomeric DNA comparing the results with those of the model monomeric G4. Time-resolved fluorescence, circular dichroism, isothermal titration calorimetry and molecular modeling were used to elucidate binding features. Ligand fluorescence lifetime and induced circular dichroism unveiled occupancy of the binding site at the interface. Thermodynamic parameters confirmed the hypothesis as they remarkably change for the dyad complexes of the monomeric and dimeric telomeric G4. The bi-functional ligand structure of the dyads is a fundamental requisite for binding at the G4 interface as only the dyads engage in complexes with 1 : 1 stoichiometry, lodging in the pocket at the interface and establishing multiple interactions with the DNA skeleton. In the absence of NMR and crystallographic data, our study affords important proofs of binding at the interface pocket and clues on the role played by the ligand structure.     

Product Gauss quadrature rules vs. cubature rules in the meshless local Petrov–Galerkin method

A crucial point in the implementation of meshless methods such as the meshless local Petrov–Galerkin (MLPG) method is the evaluation of the domain integrals arising over circles in the discrete local weak form of the governing partial differential equation. In this paper we make a comparison between the product Gauss numerical quadrature rules, which are very popular in the MLPG literature, with cubature formulas specifically constructed for the approximation of an integral over the unit disk, but not yet applied in the MLPG method, namely the spherical, the circularly symmetrical and the symmetric cubature formulas. The same accuracy obtained with 64×64 points in the product Gauss rules may be obtained with symmetric quadrature formulas with very few points.     

Detection of Significant Aprotic Solvent Effects on the Conformational Distribution of Methyl 4‐Nitrophenyl Sulfoxide: From Gas‐Phase Rotational to Liquid‐Crystal NMR Spectroscopy

The conformational equilibrium of methyl 4‐nitrophenyl sulfoxide (MNPSO) was experimentally investigated in the gas phase by using microwave spectroscopy and in isotropic and nematic liquid‐crystal solutions, in which the solvents are nonaqueous and aprotic, by using NMR spectroscopy; moreover, it was theoretically studied in vacuo and in solution at different levels of theory. The overall set of results indicates a significant dependence of the solute conformational distribution on the solvent dielectric permittivity constant: when dissolved in low‐polarity media, the most stable conformation of MNPSO proved to be strongly twisted with respect to that in more polar solvents, in which the conformational distribution maximum essentially coincides with that obtained in the gas phase. We discuss a possible explanation of this behavior, which rests on electrostatic solute–solvent interactions and is supported by calculations of the solute electric dipole moment as a function of the torsional angle. This function shows that the least polar conformation of MNPSO is located at a twist angle close to that of the conformational distribution maximum found in less‐polar solvents. This fact, associated with a relatively flat torsional potential, can justify the stabilization of the twisted conformation by the less‐polar solvents.     

Facile production of multivalent enzyme-nanoparticle conjugates

Nanoparticles (NPs) enable the development of new, biologically relevant, multifunctional agents. Multifunctional NPs can mimic the invasive biological processes involved in cancer metastasis. We have demonstrated a facile and controllable method of conjugating multiple enzyme species to superparamagnetic (SPM) NPs. Horseradish peroxidase, α-glucosidase, and collagenase were conjugated to SPM NPs with a functional enzyme:NP ratio of 15:127:103:1. N-succinimidyl-S-acetylthiopropionate (SATP)-mediated addition of sulfhydryls to enzymes was achieved without significant activity loss. Conjugation of all enzymes was simultaneously accomplished using maleimide reactive groups generated from activation of amines associated with polyethylene glycol molecules on the NP surface. Cross reactivity between enzyme activity assay systems was negligible.     

Microwave irradiation effects on random telegraph signal in a MOSFET

We report on the change of the characteristic times of the random telegraph signal (RTS) in a MOSFET operated under microwave irradiation up to 40 GHz as the microwave field power is raised. The effect is explained by considering the time dependency of the transition probabilities due to a harmonic voltage generated by the microwave field that couples with the wires connecting the MOSFET. The RTS experimental data are in agreement with the prediction obtained with our model.     

The Equations of Ostwald Ripening for Dilute Systems

We consider a dilute mixture in 3D of a finite number of particles initially close to spherical, but of varying sizes, and representing one of the phases evolving according to the quasistatic dynamics. Under the scaling hypotheses that (1) typical size/typical distance and (2) deviation from sphericity/typical size are small, we associate centers and radii to each particle for the whole evolution and derive rigorously a set of ODEs fo the radii which we relate to the Lifschitz–Slyosov–Wagner theory of coarsening.