Chloroquine disrupts zinc storage granules in primary Malpighian tubule cells of Drosophila melanogaster.

Contrasting reports exist in the literature regarding the effect of chloroquine treatment on cellular zinc uptake or secretion. Here, we tested the effect of chloroquine administration in the Drosophila model organism. We show that larvae grown on a diet supplemented with 2.5 mg/ml chloroquine lose up to 50% of their stored zinc and around 10% of their total potassium content. This defect in chloroquine-treated animals correlates with the appearance of abnormal autophagolysosomes in the principal cells of the Malpighian tubules, where zinc storage granules reside. We further show that the reported increase of Fluozin-3 fluorescence following treatment of cells with 300 µM chloroquine for 1 h may not reflect increased zinc accumulation, since a similar treatment in Madin-Darby canine kidney cells results in a 36% decrease in their total zinc content. Thus, chloroquine should not be considered a zinc ionophore. Zinc supplementation plus chloroquine treatment restored zinc content both in vivo and in vitro, without correcting autophagic or other ionic alterations, notably in potassium, associated with the chloroquine treatment. We suggest that chloroquine or hydroxychloroquine administration to patients could reduce intracellular zinc storage pools and be part of the drug's mechanism of action.

Geometry-dependent DNA-TiO2 immobilization mechanism: A spectroscopic approach.

DNA nucleotides are used as a molecular recognition system on electrodes modified to be applied in the detection of various diseases, but immobilization mechanisms, as well as, charge transfers are not satisfactorily described in the literature. An electrochemical and spectroscopic study was carried out to characterize the molecular groups involved in the direct immobilization of DNA structures on the surface of nanostructured TiO2 with the aim of evaluating the influence of the geometrical aspects. X-ray photoelectron spectroscopy at O1s and P2p core levels indicate that immobilization of DNA samples occurs through covalent (POTi) bonds. X-ray absorption spectra at the Ti2p edge reinforce this conclusion. A new species at 138.5eV was reported from P2p XPS spectra analysis which plays an important role in DNA-TiO2 immobilization. The POTi/OTi ratio showed that quantitatively the DNA immobilization mechanism is dependent on their geometry, becoming more efficient for plasmid ds-DNA structures than for PCR ds-DNA structures. The analysis of photoabsorption spectra at C1s edge revealed that the molecular groups that participate in the C1s→LUMO electronic transitions have different pathways in the charge transfer processes at the DNA-TiO2 interface. Our results may contribute to additional studies of immobilization mechanisms understanding the influence of the geometry of different DNA molecules on nanostructured semiconductor and possible impact to the charge transfer processes with application in biosensors or aptamers.

The Critical Role of Thioacetamide Concentration in the Formation of ZnO/ZnS Heterostructures by Sol-Gel Process.

ZnO/ZnS heterostructures have emerged as an attractive approach for tailoring the properties of particles comprising these semiconductors. They can be synthesized using low temperature sol-gel routes. The present work yields insight into the mechanisms involved in the formation of ZnO/ZnS nanostructures. ZnO colloidal suspensions, prepared by hydrolysis and condensation of a Zn acetate precursor solution, were allowed to react with an ethanolic thioacetamide solution (TAA) as sulfur source. The reactions were monitored in situ by Small Angle X-ray Scattering (SAXS) and UV-vis spectroscopy, and the final colloidal suspensions were characterized by High Resolution Transmission Electron Microscopy (HRTEM). The powders extracted at the end of the reactions were analyzed by X-ray Absorption spectroscopy (XAS) and X-ray diffraction (XRD). Depending on TAA concentration, different nanostructures were revealed. ZnO and ZnS phases were mainly obtained at low and high TAA concentrations, respectively. At intermediate TAA concentrations, we evidenced the formation of ZnO/ZnS heterostructures. ZnS formation could take place via direct crystal growth involving Zn ions remaining in solution and S ions provided by TAA and/or chemical conversion of ZnO to ZnS. The combination of all the characterization techniques was crucial to elucidate the reaction steps and the nature of the final products.

Electronic structure determination using an assembly of conventional and synchrotron techniques: The case of a xanthate complex.

The electronic properties of the coordination complex nickel (II) bis-n-propylxanthate, Ni(CH3(CH2)2OC(S)S)2, were studied by a combination of complementary experimental (both laboratory and synchrotron based techniques) and theoretical methods. Energy differences between HOMOs and LUMOs were determined from UV-visible spectroscopy. The assignment of the transitions were performed with the aid of TD-DFT calculations and based in symmetry considerations. The analysis of the Raman excitation profiles of selected vibrational modes of the complex, taken in resonance with a particular electronic transition, was found to reinforce the electronic assignment. Experimental binding energies of inner and core electrons were determined by PES measurements. Ni K-edge, S K-edge, Ni L-edge, O K-edge and C K-edge XANES spectra were interpreted in terms of the promotion of core electrons to unoccupied electronic levels. An experimental quantitative molecular orbital diagram was constructed using the information extracted from the different techniques.

Thermally induced anchoring of fullerene in copolymers with Si-bridging atom: Spectroscopic evidences.

We use X-ray photoelectron spectroscopy (XPS), Near-edge X-ray absorption fine structure (NEXAFS), resonant Auger spectroscopy (RAS), Attenuation Total Reflection Infrared (ATR-IR) and Atomic Force Microscopy (AFM) to study the blend between the copolymer poly[2,7-(9,9-bis(2-ethylhexyl)-dibenzosilole)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PSiF-DBT) and the fullerene derivative PC71BM submitted to different annealing temperatures. Those measurements indicate that there is an incidental anchoring of a fullerene derivative to the Si-bridging atoms of a copolymer induced by thermal annealing of the film. Insights about the physical properties of one possible PSiF-DBT/PC71BM anchored structure are obtained using Density Functional Theory calculations. Since the performance of organic photovoltaic based on polymer-fullerene blends depends on the chemical structure of the blend components, the anchoring effect might affect the photovoltaic properties of those devices.