Fluorophore-encapsulated solid-supported bilayer vesicles: a method for studying membrane permeation processes

This letter describes a new method for studying the interaction of the membrane-lysing enzyme phospholipase A(2) (PLA(2)) with phospholipid bilayers by simultaneous measurements of enzyme binding and vesicle lysis using surface plasmon resonance (SPR) and permeabilization using surface plasmon field-enhanced fluorescence spectroscopy (SPFS). The PLA(2) inhibitor dimethyl-eicosadienoic acid was incorporated into the surface-bound vesicles and support bilayer in order to study its role in preventing PLA(2)-mediated vesicle lysis. This methodology has a generic applicability for the study of a range of membrane-disrupting agents.     

Canonical and microcanonical Monte Carlo simulations of lattice-gas mixtures

We propose strict canonical and microcanonical Monte Carlo algorithms for an arbitrary lattice-gas binary mixture. We deduce formulas that allow us to obtain field quantities over the ensembles in which their conjugate extensive quantities are conserved. As an example, we have considered a lattice-gas mixture that is equivalent to the spin-1 Blume-Emery-Griffiths model [Phys. Rev. A 4, 1071 (1971)]. For a finite system and near a phase coexistence, the field as a function of its extensive conjugate shows a loop that disappears in the thermodynamic limit giving rise to the usual tie line. The first-order phase transition was determined by the use of three criteria.     

In Vitro Photodynamic Activity of 5,15-bis(3-Hydroxyphenyl)porphyrin and Its Halogenated Derivatives Against Cancer Cells

5,15-Diarylporphyrins ( 1-5 ) with hydroxyl groups and halogens as substituents were prepared by condensation between unsubstituted dipyrromethane and halogenated m -hydroxybenzaldehydes. Photophysical properties show that the nonhalogenated porphyrin 1 has higher fluorescence yield but lower singlet oxygen formation quantum yield than the halogenated derivatives due to the heavy atom effect. The in vitro activity of these derivatives was tested against WiDr colorectal adenocarcinoma and A375 melanoma cancer cells. All porphyrins present a much higher phototoxicity than Photofrin^® with IC ₅₀ values lower than the 50 n m level for WiDr cells and 25 n m level for A375 cancer cells. The most photoactive compound is the nonhalogenated porphyrin 1 which also presents the highest uptake. Halogenated derivatives present much lower uptakes than 1 . However, their photoactivity is similar to compound 1 showing that their intrinsic photoactivity (ISP) is very high. Iodinated compound 4 presents the highest ISP. The greater ability of these porphyrins to destroy cancer cells could be related to their photophysical and photochemical properties.     

Evaluation of measurement uncertainties for the determination of total metal content in soils by atomic absorption spectrometry

In this work estimation of measurement uncertainties associated with the total metal content in soils was done by an intralaboratory approach based on method validation and quality control data, and using two certified reference materials (CRM). CRM and soil samples were analyzed following procedures based on the methods that are applied to silicate materials. All elements were determined by atomic absorption spectrometry following a quality assurance program previously established. Quality control actions were implemented in order to provide reliable data. The precision under within-laboratory reproducibility conditions was estimated from triplicate analysis. The trueness component was determined as recovery of the analyte from CRMs: soil sample, SO-2 and river clay sediment, LGC 6139. Combined measurement uncertainty was expressed in terms of precision and recovery uncertainties and the later further split on CRM replicate analysis and uncertainty of the certified value components. The results obtained are critically discussed on the basis of the different contributions. For the selection of the reference material, the CRM dependent terms are critically compared in order to fulfill specific requirements. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Thermal stability and water content determination of glycerol by thermogravimetry

During the last years, the demand for biofuels has increased significantly. In Brazil, a production of 1 billion liters of biodiesel was produced by the end of 2007, due to its obligatory use in the composition of the diesel for vehicle use. In this production, a hundred thousand tons of glycerol are produced as by-product, for which alternative uses are needed. As glycerol has already been studied by other conventional characterization methods in the past, thermal analysis has been used mostly for characterization of sub ambient temperature properties of glycerol. In this paper, thermogravimetry (TG), derivative thermogravimetry (DTG) and differential thermal analysis (DTA) were used for its thermal characterization above room temperature. Thermal stability was determined from experimental data, which show that even in air, only a very small part of the volatilized glycerol is burned out. A thermogravimetric quantitative method was developed to determinate the water content of glycerol–water mixtures, which also was used to quantify the water impurity in pro-analysis samples of glycerol, showing compatible results with those obtained by Karl Fischer method.     

Seismic denoising using curvelet analysis

A curvelet is a new and effective spectral transform, that allows sparse representations of complex data. It has many applications in several fields, including denoising, wave propagation in disordered media and pattern recognition. This spectral technique is based on directional basis functions that represent objects having discontinuities along smooth curves. In this work we apply this technique to the removal of Ground Roll, which is an undesired feature signal present in seismic data obtained by sounding the geological structures of the Earth. In this methodology the original seismic data is decomposed by curvelet transform in scales and angular domains. For each scale the curvelet denoising technique allows a very efficient separation of the Ground Roll in angle sections. The precise identification of the Ground Roll pattern allows an effective erasing of its coefficients. In contrast to conventional denoising techniques we do not use any artificial attenuation factor to decrease the amplitude of the Ground Roll coefficients. We have estimated that, depending on the scale, around 75% of the energy of the strong undesired signal is removed.     

Lexicographic optimization for the multi-container loading problem with open dimensions for a shoe manufacturer

4OR - Motivated by a real-world application, we present a multi-container loading problem with 3-open dimensions. We formulate it as a biobjective mixed-integer nonlinear program with lexicographic...