Evidence of bilayer structure in V2O5 xerogel

Polarized X-ray absorption spectroscopy has been used to study the short-range structure of deposited films of V2O5 xerogel. The material is characterized by a layer of VO5 units with the V-O apical bond perpendicular to the basal (xy) plane. We have focused our attention along the z axis. Experiments were carried out by extended X-ray absorption fine structure (EXAFS) spectroscopy in a grazing incidence geometry and showed evidence for close interactions between neighboring layers of V2O5. The structure is described by two sheets of V2O5 facing each other. Fitting of the EXAFS data has confirmed the existence of a vanadium-vanadium interaction between two different V2O5 layers and an oxygen bridge between them.     

Pure copper vs. mixed copper and palladium hexacyanoferrates for glucose biosensing applications

A glucose amperometric biosensor was developed. Glucose oxidase enzyme was immobilized by means of a Nafion membrane on glassy carbon modified with an electrochemically deposited mixed Cu and Pd hexacyanoferrate (CuPdHCF). According to the data provided by X-ray atomic spectroscopy measurements, this Cu- and Pd-based hexacyanoferrate is likely to be a mixture of single CuHCF and PdHCF pure phases. The biosensor performances were evaluated by recording the steady-state currents due to submillimolar additions of glucose to a potassium buffer solution (pH 5.5) and exploiting the electrocatalytic reduction of the enzymatically produced hydrogen peroxide. The CuPdHCF-based biosensor exhibited a sensitivity of 8.1?±?0.6 A M^?1 m^?2, a limit of detection of 1.4?×?10^?5 M, and a linear response range extending between 5?×?10^?5 and 4?×?10^?4 M, with a dynamic response range up to 4?×?10^?3 M glucose. Electrode sensitivity and signal stability resulted more satisfactory as compared to those of a CuHCF-based biosensor fabricated according to the same procedure. The selectivity was investigated through an interference study. The response to easily oxidizable species was found to be low enough to allow glucose determination in biological samples.     

2-DE and MALDI-TOF-MS for a comparative analysis of proteins expressed in different cellular models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal, neurodegenerative disorder characterized by the selective loss of motor neurons from the spinal cord and brain. About 10% of ALS cases are familial (FALS), and in 20% of these cases the disease has been linked to mutations in the Cu,Zn-SOD1 gene. Although the molecular mechanisms causing these forms of ALS are still unclear, evidence has been provided that motor neurons injuries associated with mutant superoxide dismutase (SOD1)-related FALS result from a toxic gain-in-fuction of the mutated enzyme. To understand better the role of these mutations in the pathophysiology of FALS we have compared the pattern of proteins expressed in human neuroblastoma SH-SY5Y cell line with those of cell lines transfected with plasmids expressing the wild-type human SOD1 and the H46R and G93A mutants. 2-DE coupled to MALDI-TOF-MS were the proteomic tools used for identification of differentially expressed proteins. These included cytoskeletal proteins, proteins that regulate energetic metabolism and intracellular redox conditions, and the ubiquitin proteasome system. The proteomic approach allowed to expand the knowledge on the pattern of proteins, with altered expression, which we should focus on, for a better understanding of the possible mechanism involved in mutated-SOD1 toxicity. The cellular models considered in this work have also evidenced biochemical characteristics common to other SOD1-mutated cellular lines connected to the pathogenesis of ALS.     

Structural characterization of electrodeposited copper hexacyanoferrate films by using a spectroscopic multi-technique approach

A deep structural investigation predominantly by X-ray spectroscopic techniques is conducted on films of copper hexacyanoferrate (CuHCF) deposited under different conditions, aimed at establishing structure-properties relationships. We show that the potentiodynamic electrosynthesis of CuHCF on carbon-based surfaces produces a highly disordered material, with a variable amount of Prussian Blue (PB). The subsequent Cu(2+) intercalation induces the partial conversion of PB into CuHCF, which explains the improved electrocatalytic properties after the intercalation process. Both Cu and Fe K-edge data have been recorded. For the sample with the lower amount of PB, we could perform a multiple edge data analysis to determine the local atomic environment around both metal centres using the same set of structural parameters. The presence of high multiplicity Cu-N-C-Fe linear chains has allowed us to determine accurately the local environment of Fe while fitting the Cu K-edge data only. Using this approach we have retrieved structural information around Fe for those samples in which the concomitant presence of PB would have made impossible the analysis of the Fe K-edge. The Fe-C, C-N and Cu-N bond distances have been found in agreement with those of the bulk structures, but higher values of [Fe(CN)(6)] vacancies for the building blocks have been evidenced, reaching a value of ~45% in one sample. XANES, Raman and SEM data agree with the model proposed for each studied electrode.     

Capillary electrophoresis investigation of a partially unfolded conformation of beta(2)-microglobulin

Dialysis-related amyloidosis is a disease in which partial unfolding of beta(2)-microglobulin plays a key pathogenetic role in the formation of the amyloid fibrils. We have recently demonstrated that a partially unfolded conformer of beta(2)-microglobulin is involved in fibrillogenesis and that this species is significantly populated under physiological conditions. In this work capillary electrophoresis has been used to measure the equilibrium between the native protein and this conformer in samples known to have a higher or lower amyloidogenic potential, namely full-length beta(2)-microglobulin, two truncated species and a mutant, created by replacing histidine in position 31 with thyrosine. In addition, for all protein species folding stability experiments have been carried out by monitoring the secondary structure by circular dichroism at increasing concentrations of guanidinium chloride. The values of free energy of unfolding in the absence of denaturant, obtained by elaboration of these experiments, were found to be inversely correlated to the area percent of the partially unfolded conformer, as measured by capillary electrophoresis. Affinity capillary electrophoresis experiments have been also carried out under nondenaturing conditions to assess the affinity of copper and suramin to either the native form or the conformational intermediate of full-length beta(2)-microglobulin.     

Sulfonated molecules that bind a partially structured species of beta2-microglobulin also influence refolding and fibrillogenesis

Human beta2-microglobulin (beta2-m) is a small amyloidogenic protein responsible for dialysis-related amyloidosis, which represents a severe complication of long-term hemodialysis. A therapeutic approach for this amyloidosis could be based on the stabilization of beta2-m through the binding to a small molecule, to possibly inhibit protein misfolding and amyloid fibril formation. The search of a strong ligand of this protein is extremely challenging: by using CE in affinity and refolding experiments we study the effect that previously selected sulfonated molecules have on the equilibrium between the native form and an ensemble of conformers populating the slow phase of beta2-m folding. These data are correlated with the effect that the same molecules exert on in vitro fibrillogenesis experiments.     

Ag nanoparticles obtained by pulsed laser ablation in water: surface properties and SERS activity

We studied the surface properties and reactivity of silver nanoparticles obtained by picosecond or nanosecond pulsed laser ablation in water and with 1064‐nm wavelength. Ultraviolet–visible spectroscopy results and subsequent modelling by Mie theory indicated the presence of an oxide layer on the nanoparticle surface, which favours the colloidal stability, but reduces the interaction with the environment. The oxide layer is also responsible for the reduced surface enhanced Raman spectroscopy (SERS) activity of these colloids with respect to those obtained by chemical reduction. However, SERS activation can be efficiently obtained by addition of chloride ions to the colloids, leading to SERS enhancement factors that are comparable with those of the chemically prepared counterparts. Copyright © 2015 John Wiley & Sons, Ltd.     

Nitroimidazole and glucosamine conjugated heteroscorpionate ligands and related copper(II) complexes. Syntheses, biological activity and XAS studies

New nitroimidazole and glucosamine conjugated heteroscorpionate ligands, namely 2,2-bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide (L(MN)) and 1,3,4,6-tetra-O-acetyl-2-{[bis(3,5-dimethyl-1H-pyrazol-1-yl)acetyl]amino}-2-deoxy-β-D-glucopyranose (L(DAC)), respectively, were synthesized by direct coupling of preformed side chain acid and amine components. The related copper(II) complexes {[(L(MN))(2)Cu]Cl(2)}, and {[(L(DAC))(2)Cu]Cl(2)} have been prepared from the reaction of CuCl(2)*2H(2)O with L(MN) or L(DAC) ligand in methanol solution. Single crystal structural characterization was undertaken for the L(MN) ligand. In the absence of a coordinated metal core, the overall arrangement of the ligand is determined by some loose intra- and inter-molecular nonbonding contacts. X-Ray Absorption Spectroscopy (XAS) has been used to probe the local structure of the two copper(II) complexes, {[(L(MN))(2)Cu]Cl(2)} and {[(L(DAC))(2)Cu]Cl(2)}. The EXAFS analysis has permitted the identification of the local environment of the copper site. Copper interacts with 2 units of ligand in both complexes, and it is found to be 6-fold coordinated. Its local structure is described by four Cu-N and two Cu-O interactions to form a pseudo-octahedron core, with a 0.14 ? lengthening of the Cu-O bond length in the case of L(DAC) complex with respect to the L(MN) one, likely due to the higher steric hindrance of the glucosamine moiety. The XANES analysis agrees with these results, also confirming the Cu(II) formal copper oxidation state for both complexes. The new copper(II) complexes {[(L(MN))(2)Cu]Cl(2)} and {[(L(DAC))(2)Cu]Cl(2)} as well as the corresponding uncoordinated ligands were evaluated for their cytotoxic activity towards a panel of several human tumour cell lines. The results reported here indicate that both copper(II) complexes show similar spectra of cytotoxicity and very low resistance factors (RF < 2) against C13* ovarian cancer cells which have acquired resistance to cisplatin.     

Screening of fibrillogenesis inhibitors of β2-microglobulin: integrated strategies by mass spectrometry capillary electrophoresis and in silico simulations

The challenging search of ligands for the amyloidogenic protein β₂-microglobulin led us to set up an integrated strategy that combines analytical techniques and molecular modelling. Using a chemical library composed of 90 sulphonated molecules and a novel MS screening approach, we initially single out a few new binders. To check for anti-amyloid activity, the best hit obtained was thoroughly studied by docking analysis, affinity and refolding experiments by capillary electrophoresis and in vitro fibrillogenesis Thioflavin T test. Correlative analysis of the overall results obtained from the MS screening led to develop an equation able to identify the key factors of the affinity for β₂-microglobulin and to predict the affinity for novel derivatives. The proposed equation was then used for a virtual screening of a large compound database. Studies on the new hit thus retrieved confirm the predictive potential of both the equation on affinity and of docking analysis on anti-amyloid activity.     

The effects of nano-TiO<Subscript>2</Subscript> on seed germination,development and mitosis of root tip cells of <Emphasis Type="Italic">Vicia narbonensis</Emphasis> L. and <Emphasis Type="Italic">Zea mays</Emphasis> L

This study aimed to provide new information about phyto-toxicology of nano-TiO₂ on plant systems. To contribute to the evaluation of the potential harmful effects of the nanoparticles on monocots and dicots we considered their effects on seed germination and root elongation applying a concentration range from 0.2 to 4.0‰ in the plants Zea mays L. and Vicia narbonensis L. Moreover, we achieved a genotoxicity study at cytological level in root meristems by means of traditional cytogenetic approach, to evidence possible alterations in mitotic activity, chromosomal aberrations, and micronuclei release. From these analyses it comes out that nano-TiO₂ particles, after short-term exposure and under our experimental conditions, delayed germination progression for the first 24 h in both materials. Root elongation was affected only after treatment with the higher nano-TiO₂ concentration. Further significant effects were detected showing mitotic index reduction and concentration-dependent increase in the aberration emergence that evidenced a nano-TiO₂-induced genotoxic effect for both species.