Controlling E. coli adhesion on high-k dielectric bioceramics films using poly(amino acid) multilayers

The influence of high-k dielectric bioceramics with poly(amino acid) multilayer coatings on the adhesion behavior of Escherichia coli (E. coli) was studied by evaluating the density of bacteria coverage on the surfaces of these materials. A biofilm forming K-12 strain (PHL628), a wild-type strain (JM109), and an engineered strain (XL1-Blue) of E. coli were examined for their adherence to zirconium oxide (ZrO(2)) and tantalum oxide (Ta(2)O(5)) surfaces functionalized with single and multiple layers of poly(amino acid) polyelectrolytes made by the layer-by-layer (LBL) deposition. Two poly(amino acids), poly(l-arginine) (PARG) and poly(l-aspartic acid) (PASP), were chosen for the functionalization schemes. All three strains were found to grow and preferentially adhere to bare bioceramic film surfaces over bare glass slides. The bioceramic and glass surfaces functionalized with positively charged poly(amino acid) top layers were observed to enhance the adhesion of these bacteria by up to 4-fold in terms of bacteria surface coverage. Minimal bacteria coverage was detected on surfaces functionalized with negatively charged poly(amino acid) top layers. The effect of different poly(amino acid) coatings to promote or minimize bacterial adhesion was observed to be drastically enhanced with the bioceramic substrates than with glass. Such observed enhancements were postulated to be attributed to the formation of higher density of poly(amino acids) coatings enabled by the high dielectric strength (k) of these bioceramics. The multilayer poly(amino acid) functionalization scheme was successfully applied to utilize this finding for micropatterning E. coli on bioceramic thin films.     

Photoinduced water oxidation by a tetraruthenium polyoxometalate catalyst: ion-pairing and primary processes with Ru(bpy)3(2+) photosensitizer

The tetraruthenium polyoxometalate [Ru(4)(μ-O)(4)(μ-OH)(2)(H(2)O)(4)(γ-SiW(10)O(36))(2)](10-) (1) behaves as a very efficient water oxidation catalyst in photocatalytic cycles using Ru(bpy)(3)(2+) as sensitizer and persulfate as sacrificial oxidant. Two interrelated issues relevant to this behavior have been examined in detail: (i) the effects of ion pairing between the polyanionic catalyst and the cationic Ru(bpy)(3)(2+) sensitizer, and (ii) the kinetics of hole transfer from the oxidized sensitizer to the catalyst. Complementary charge interactions in aqueous solution leads to an efficient static quenching of the Ru(bpy)(3)(2+) excited state. The quenching takes place in ion-paired species with an average 1:Ru(bpy)(3)(2+) stoichiometry of 1:4. It occurs by very fast (ca. 2 ps) electron transfer from the excited photosensitizer to the catalyst followed by fast (15-150 ps) charge recombination (reversible oxidative quenching mechanism). This process competes appreciably with the primary photoreaction of the excited sensitizer with the sacrificial oxidant, even in high ionic strength media. The Ru(bpy)(3)(3+) generated by photoreaction of the excited sensitizer with the sacrificial oxidant undergoes primary bimolecular hole scavenging by 1 at a remarkably high rate (3.6 ± 0.1 × 10(9) M(-1) s(-1)), emphasizing the kinetic advantages of this molecular species over, e.g., colloidal oxide particles as water oxidation catalysts. The kinetics of the subsequent steps and final oxygen evolution process involved in the full photocatalytic cycle are not known in detail. An indirect indication that all these processes are relatively fast, however, is provided by the flash photolysis experiments, where a single molecule of 1 is shown to undergo, in 40 ms, ca. 45 turnovers in Ru(bpy)(3)(3+) reduction. With the assumption that one molecule of oxygen released after four hole-scavenging events, this translates into a very high average turnover frequency (280 s(-1)) for oxygen production.     

Mechanism of Ni2+ and NiOH+ interaction with hydroxamic acids in SDS: evaluation of the contributions to the equilibrium and rate parameters in the aqueous and micellar phase

The equilibria and kinetics (stopped-flow) of the binding of Ni(II) to salicylhydroxamic acid (SHA) and phenylbenzohydroxamic acid (PBHA) have been investigated in aqueous solutions containing SDS micelles. The two ligands are fairly distributed between the two pseudophases present, so the binding reaction occurs in both phases. The contributions to the total reaction from each phase has been evaluated, following a procedure where use is made of the experimentally determined partition coefficients of the reactants involved. The mechanism of the reaction occurring on the micelle surface has been derived and comparison with the mechanism in water shows that the step Ni(2+) + HL ? NiHL(2+) is operative in both pseudophases, whereas the step Ni(2+) + L(-)? NiL(+), which is operative in water, is replaced in SDS by the step NiOH(+) + HL ? NiL(+). The analysis of the equilibrium and of the kinetic data enabled the evaluation of the equilibrium and the rate constants of the individual steps taking part in the binding process over the micelle surface. Interestingly, the first hydrolysis constant of the Ni(H(2)O)(6)(2+) ion in SDS is more than two orders of magnitude higher than in water. The agreement between the equilibrium constants derived from kinetics and those obtained by static measurements confirms the validity of the proposed mechanism.     

Tilted objects EFI extracted at once by 3D output of the angular spectrum method

Since many optical imaging systems suffer from a limited depth of focus, three-dimensional (3D) objects, or even flat objects tilted with respect to the optical axis, are imaged with only a portion of them in focus. Typically, to overcome this problem, in-focus areas are extracted from different images taken at different depths. The in-focus regions are thus merged together to build the extended focus image (EFI). In this work, we propose a quasi-automatic method for the EFI construction of tilted objects, extracted at once by 3D output of the Angular Spectrum Method (ASM) from a single digitally recorded hologram. Results show that our method can be effectively used for the correction of the anamorphism due to the reconstruction on a tilted plane with respect to the hologram one.     

Nuclear magnetic resonance in contemporary art: the case of “Moon Surface” by Turcato

Nuclear Magnetic Resonance (NMR) methodologies were applied to characterize the constitutive materials and the state of degradation of a contemporary painting. The investigation was mandatory to plan a suitable restoration. Noninvasive, portable NMR allowed the detection of degraded regions of the painting based on the measurement of longitudinal relaxation time. A few samples were investigated by high resolution solid state NMR and NMR in solution, which allowed us to identify the polyurethane constituting the artefact, to investigate the microstructure in detail, and to assess that the degradation process mostly affected the ethylene units used to cap the polypropylene oxide polymeric chain. As a matter of fact, a shortening of longitudinal relaxation time was accompanied by a degradation of ethylene units. The degradation of the inorganic loading was investigated by ²⁷Al MAS, which evidenced the absence of penta-coordinated aluminum in degraded samples.     

On the structure of the directions not determined by a large affine point set

Given a point set U in an n-dimensional affine space of size q ^n?1?ε, we obtain information on the structure of the set of directions that are not determined by U, and we describe an application in the theory of partial ovoids of certain partial geometries.     

Phosphoric acid mediated tautomerism of imines: addition of a secondary enamine intermediate to aldehydes

A phosphoric acid derivative has been shown to promote the addition between an imine and several aldehyde substrates through an enamine intermediate to give cross-aldol condensation products. The reaction scope and preliminary mechanistic investigations will be presented.     

Chitosan-Polyoxometalate Nanocomposites: Synthesis,Characterization and Application as Antimicrobial Agents

Polyoxometalates (POMs) were used, together with chitosan (CS), to obtain hybrid nanoaggregates. Three representative POMs were efficiently assembled into nanoparticles of few hundred nm diameter, featuring entangled ribbons substructure. In order to establish suitable preparation and stability conditions, the assemblies were characterized in solution by UV–Vis spectroscopy, dynamic light scattering and ζ-potential. The nanoparticles were tested against E. coli (10⁶ CFU/ml) in aqueous solution, showing a synergic activity of the heteropolyacid H₅PMo₁₀V₂O₄₀ and CS. For such components, a highly porous and antibacterial film was obtained upon lyophilisation of the colloidal mixture.     

Direct catalytic synthesis of enantiopure 5-substituted oxazolidinones from racemic terminal epoxides

A venerable scaffold for asymmetric synthesis and drug development, chiral 5-substituted oxazolidinones are obtained in almost enantiomerically pure form (up to 99.9% ee) starting from racemic terminal epoxides. The salient features of this process include the very simple and convenient experimental protocol and the employment of a readily accessible catalyst and inexpensive, easily handled starting materials. An enantioconvergent approach for the total conversion of racemic epoxide into a single stereoisomeric oxazolidinone is also described.     

Copper(II) chloride complexes of 2-(4′-Methyl-2′-pyridyl)-benzoxazole,their sulphur and nitrogen analogues and 2-(4′-Methyl-2′ {or8′} -quinolyl)benzoxazoles

Summary Copper(II) complexes CuLCl₂, where L=2-(4-methyl-2-pyridyl)benzimidazole(mpbi); 2-(4-methyl-2-pyridyl)benzothiazole(mpbt); 2-(4-methyl-2-pyridyl)benzoxazole (mpbo); 2-(4-methyl-2-quinolyl)benzoxazole (mqbo); 2-(4-methyl8-quinolyl)benzoxazole (mqbo), and Cu(mpbi)₂Cl₂(H₂O) have been synthesized and characterized by conductivity and magnetic measurements as well as by i.r., electronic and e.s.r. spectra. The ligands are bidentate donors through the pyridine and isoxazole nitrogen atoms. The CuLCl₂ complexes exhibit spectral properties consistent with CuN₂Cl₂ chromophores differing in the degree of tetrahedral distortion, which is found to parallel the steric hindrance near the donor sites. Cu(mpbi)₂ Cl₂(H₂O) is five-coordinate.