Smiles rearrangement for the synthesis of 5-amino-substituted [1]benzothieno[2,3-b]pyridine

The Smiles rearrangement was successfully applied to 4-hydroxybenzo[b]thiophene furnishing a facile entry to the 4-amino derivative. The rearrangement was extended to 5-methoxy-4-methoxycarbonyl[1]benzothieno[2,3-b]pyridine obtained via aza-Wittig/electrocyclization reaction of novel N-(4-methoxybenzothiophen-2-yl)iminomethyldiphenylphosphorane with methyl trans-4-oxo-2-pentenoate. The preparation of a novel 5-amino-4-methoxycarbonyl[1]benzothieno[2,3-b]pyridine, which is of interest as a potential secondary peptide structure mimic, was successfully achieved.     

A Non‐Enzymatic Carbohydrate Sensor Based on Multiwalled Carbon Nanotubes Modified with Adsorbed Active Gold Particles

The voltammetric behavior of a glassy carbon electrode modified with multiwalled carbon nanotubes (MWCNTs) and Au particles was studied in alkaline medium towards the electrooxidation of some carbohydrates used as model compounds. The influence of carbohydrate concentration and scan rate on peak potentials, peak currents, etc., observed at the modified electrode was evaluated and critically discussed. The Au particles dispersed into multiwalled carbon nanotubes structures showed favorable electrocatalytic and analytical properties towards the electrooxidation of xylose and glucose molecules. Atomic force microscopy performed on the resulting modified electrode showed a well‐efficient 3D distribution of Au active particles having sharp‐edged and elongated grains along bundles of the MWCNTs. The three‐dimensional MWCNT‐Au composite structure of the catalyst act as a promoter to enhance the diffusive character of recorded currents and probably also increases the rate of the heterogeneous electron transfer of the electrooxidation process considered.     

High-resolution 2-DE for resolving proteins, protein adducts and complexes in plasma

A 2-DE system has been devised in which proteins are first separated in their native state followed by separation according to mass under denaturing conditions (Nat/SDS-PAGE). Hydrophilic properties of the gel and the presence of dihydroxybisacrylamide in the first dimension allowed a good resolution for high-molecular-weight proteins and maintained interactions. With this method 252 plasma spots have been resolved and 140 have been characterized by MS as isoforms of 60 proteins, a relevant part of which (12) were not detected by traditional 2-D gels or by other nondenaturing 2-D techniques. The list includes complement factors (C4d, C7), coagulation factors (coagulation factor II, fibrin beta), apolipoproteins (apolipoprotein B) and cell debris (vinculin, gelsolin, tropomyosin, dystrobrevin beta, fibrinectin I). Nat/SDS PAGE also allowed separation of nicked forms of albumin, Apo B100 and alpha2-macroglobulin and showed the presence of atypical albumin adducts corresponding to post-translational and oxidation products. Our system provides therefore new tools for resolving proteins, protein aggregates and complexes and amplifies the potentiality of traditional electrophoretic analysis.     

A novel amperometric biosensor based on a co-crosslinked l-lysine-α-oxidase/overoxidized polypyrrole bilayer for the highly selective determination of l-lysine

An amperometric biosensor for the determination of l-lysine based on l-lysine-α-oxidase immobilized by co-crosslinking on a platinum electrode previously modified by an overoxidized polypyrrole film is described. The optimization of experimental parameters, such as pH and flow rate, permitted to minimize significantly substrate interferences even using a low specific, commercial enzyme. The relevant biases introduced in the measurement of lysine were just about 1% for l-arginine, l-histidine and l-ornithine, roughly 4% for l-phenylalanine and l-tyrosine. The developed approach allowed linear lysine responses from 0.02 mM up to 2 mM with a sensitivity of 41 nA/(mM × mm²) and a detection limit of 4 μM (S/N = 3). No appreciable loss in lysine sensitivity was observed up to about 40 days. Allowing polypyrrole layer to remove interference from electroactive compounds, the present method revealed suitable to detect l-lysine in a pharmaceutical and cheese sample, showing a good agreement with the expected values.     

[M(bpy)3] (M = Fe,Ru, Os): New Crystalline Materials from the reductive electrocrystallization of [M(bpy)3](PF6)2

Reductive electrocrystallization at a constant current density (11.0–11.5 μA/cm²) of millimolar solutions of [M(bpy)₃](PF₆)₂, where M = Fe, Ru, or Os, and bpy = 2,2′-bipyridine in acetonitrile containing 0.1M Bu₄NPF₆ results in the formation of dark crystals on the Pt cathode. The crystals grow as long, thin, and shiny needles having a hexagonal cross section of 0.1–0.5 mm in diameter. Combustion microanalyses results are consistent with the composition for [Fe(bpy)₃], [Ru(bpy)₃], and [Os(bpy)₃]. In addition, the chromophores are conserved, as confirmed by recording both the electronic and the ¹H-NMR spectra after reoxidation of the electrocrystals in humid air. The spectra are identical to those for authentic samples of [Fe(bpy)₃]²⁺, [Ru(bpy)₃]²⁺, and [Os(bpy)₃]²⁺. A ratio of 2.0 ± 0.1 e^?/molecule is observed upon completion of the controlled potential electrolysis of a solution of [M(bpy)₃]²⁺, which results in the precipitation of a dark solid and the almost complete fading of the color of the original solution. Unexpectedly, the crystals do not exhibit an ESR signal. These data indicate the formation of novel materials, crystalline [Fe(bpy)₃], [Ru(bpy)₃], and [Os(bpy)₃].     

Synthesis of some dibenzodiazepinone derivatives as potent and m2-selective antimuscarinic compounds

Two series of 5-[[4-[4-(dialkylamino)butyl]-l-cyclohexyl]acetyl], and 5-[(dialkylamino)acyl]-10,11-dihydro-5H- dibenzo[b,e][1,4]diazepin-11-ones were synthesized as potential m2-selective ligands 1,2. Their affinity and selectivity for the muscarinic cholinergic receptor m-AChR subtypes were determined. Replacing a nitrogen with CH in the piperidine ring of 5-[[4-[4-(dialkylamino)butyl]-l-piperidinyl]acetyl]-10,11-dihydro-5H-dibenzo-[b,e][1,4]diazepin-11-ones 3 significantly altered the affinity and selectivity to the muscarinic receptor subtypes.     

A biomimetic approach to the chemical inactivation of chrysotile fibres by lichen metabolites

Some lichens were recently reported to modify the surface state of asbestos. Here we report some new insight on the physico-chemical modifications induced by natural chelators (lichen metabolites) on two asbestos samples collected in two different locations. A biomimetic approach was followed by reproducing in the laboratory the weathering effect of lichen metabolites. Norstictic, pulvinic and oxalic acid (0.005, 0.5 and 50 mM) were put in contact with chrysotile fibres, either in pure form (A) or intergrown with balangeroite, an iron-rich asbestiform phase (B). Mg and Si removal, measured by inductively coupled plasma atomic emission spectrometry (ICP-AES) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), reveals an incongruent dissolution for pure chrysotile (A), with Mg removal always exceeding that of Si, while chrysotile-balangeroite (B) follows a congruent dissolution pattern in all cases except in the presence of 50 mM oxalic acid. A much larger removal of Mg than Si in the solutions of 0.5 and 50 mM oxalic acid with chrysotile (A) suggests a structural collapse, which in the case of chrysotile-balangeroite (B) only occurs with 50 mM oxalic acid; in these cases both samples are converted into amorphous silica (as detected by X-ray diffraction (XRD)). Subsequent to incubation, some new phases (Fe(2)O(3), CaMg(CO(3))(2), Ca(C(2)O(4)) x H(2)O and Mg(C(2)O(4))2 x H(2)O), similar to those observed in the field, were detected by XRD and micro-Raman spectroscopy. The leaching effect of lichen metabolites also modifies the Fenton activity, a process widely correlated with asbestos pathogenicity: pure chrysotile (A) activity is reduced by 50 mM oxalic acid, while all lichen metabolites reduce the activity of chrysotile-balangeroite (B). The selective removal of poorly coordinated, highly reactive iron ions, evidenced by NO adsorption, accounts for the loss in Fenton activity. Such fibres were chemically close to the ones observed in the field. Chrysotile-rich rocks, colonised by lichens, could be exposed to a natural bioattenuation and considered as a transient environmental hazard.     

Influence of Cyclodextrin Complexation on the in vitro Human Skin Penetration and Retention of the Sunscreen Agent, Oxybenzone

The objective of this study was to investigate the influence of cyclodextrins on the cutaneous availability of the sunscreen oxybenzone. The interaction between oxybenzone and hydrophilic α-, β- and γ-cyclodextrin derivatives was studied in water by phase-solubility analysis. Among the available cyclodextrins, hydroxypropyl-β-cyclodextrin (HP-β-CD) and especially sulfobutylether-β-cyclodextrin (SBE-β-CD) had the greatest solubilizing activity. Ethanol–water solutions containing oxybenzone free or complexed with HP-β-CD or SBE-β-CD were applied to human skin in Franz diffusion cells and the amount of sunscreen permeated into the different cutaneous compartments was determined by HPLC. As much as 20.5% of the oxybenzone applied dose diffused within the skin tissue after 6 h application. Between 39.4% and 54.9% of the penetrated UV filter was localized in the stratum corneum, with no significant difference between uncomplexed oxybenzone or its complex with HP-β-CD. Conversely, the amount retained in the stratum corneum was markedly decreased (ca. 50%) by complexation with SBE-β-CD. Considerable quantities of oxybenzone accumulated into the viable epidermis (5.7% of the applied dose) and dermis (6.2% of the applied dose) from the preparation containing the free UV filter. The sunscreen penetration to the deeper living layers of the skin was remarkably lower (1.0% and 2.0% of applied dose for epidermis and dermis, respectively) upon application of the sunscreen complexed with SBE-β-CD, whereas HP-β-CD had no effect. In addition, photostability experiments demonstrated that SBE-β-CD complexation did not alter the sunscreen photochemical properties.     

The origins of Euler's early work on continued fractions

In this paper, I examine Euler's early work on the elementary properties of continued fractions in the 1730s, and investigate its possible links to previous writings on continued fractions by authors such as William Brouncker. By analysing the content of Euler's first paper on continued fractions, ‘De fractionibus continuis dissertatio’ (1737, published 1744) I conclude that, contrary to what one might expect, Euler's work on continued fractions initially arose not from earlier writings on continued fractions, but from a wish to solve the Riccati differential equation.     

The economic effect of interlocking directorates in Italy: new evidence using centrality measures

We use measures of vertex centrality to examine interlocking directorates and their economic effects in Italy. We employ centrality measures like degree, eigenvector centrality, betweenness, and flow betweenness, along with the clustering coefficient. We document the existence of a negative relationship between both degree and eigenvector centrality and firm value. Betweenness and flow betweenness, on the other hand, are not associated with lower firm valuations. We argue that these differences derive from the different properties of these measures: while degree and eigenvector centrality measures the influence and the power of the connections, betweenness and flow betweenness are proxies for the volume of information that passes between the nodes. This result is robust with respect to the use of both stock market and operating performance measures, as well as several controlling variables.