A Non‐damaging Method to Analyze the Configuration and Dynamics of Nitrotyrosines in Proteins

Often, deregulation of protein activity and turnover by tyrosine nitration drives cells toward pathogenesis. Hence, understanding how the nitration of a protein affects both its function and stability is of outstanding interest. Nowadays, most of the in vitro analyses of nitrated proteins rely on chemical treatment of native proteins with an excess of a chemical reagent. One such reagent, peroxynitrite, stands out for its biological relevance. However, given the excess of the nitrating reagent, the resulting in vitro modification could differ from the physiological nitration. Here, we determine unequivocally the configuration of distinct nitrated‐tyrosine rings in single‐tyrosine mutants of cytochrome c. We aimed to confirm the nitration position by a non‐destructive method. Thus, we have resorted to ¹H‐¹⁵N heteronuclear single quantum coherence(HSQC) spectra to identify the ³J(N? H) correlation between a ¹⁵N‐tagged nitro group and the adjacent aromatic proton. Once the chemical shift of this proton was determined, we compared the ¹H‐¹³C HSQC spectra of untreated and nitrated samples. All tyrosines were nitrated at ε positions, in agreement to previous analysis by indirect techniques. Notably, the various nitrotyrosine residues show a different dynamic behaviour that is consistent with molecular dynamics computations.     

Coupling of nanoporous chromium, aluminium-containing silicates with an ionic liquid for the transformation of glucose into 5-(hydroxymethyl)-2-furaldehyde

Micro/mesoporous chromium, aluminium-containing silicates of the type TUD-1 (Al-TUD-1, Cr-TUD-1, CrAl-TUD-1) and zeolite BEA, Cr-BEA, and related composites BEA/TUD-1 and Cr-BEA/TUD-1, were prepared, characterised, and tested as solid acids coupled with the ionic liquid (IL) 1-butyl-3-methylimidazolium chloride ([bmim]Cl) as solvent, in the transformation of D-glucose into 5-(hydroxymethyl)-2-furaldehyde (Hmf), at 120 °C. The chromium-containing catalytic systems lead to considerably higher Hmf yields in comparison to the related systems without chromium. The IL is a favourable solvent for this target reaction (in terms of Hmf yields reached) compared to water or dimethylsulfoxide. A detailed study on the stabilities of the nanoporous solid acids in the IL medium is presented.     

Structure and electronic properties of a benzene-water solution

Electronic properties of benzene in water were investigated by a sequential quantum mechanical/molecular dynamics approach. Emphasis was placed on the analysis of the structure, polarization effects, and ionization spectrum. By adopting a polarizable model for both benzene and water the structure of the benzene-water solution is in good agreement with data from first principles molecular dynamics. Further, strong evidence that water molecules acquire enhanced orientational order near the benzene molecule is found. Upon hydration, the quadrupole moment of benzene is not significantly changed in comparison with the gas-phase value. We are also reporting results for the dynamic polarizability of benzene in water. Our results indicate that the low energy behaviour of the dynamic polarizability of gas-phase and hydrated benzene is quite similar. Outer valence Green's function calculations for benzene in liquid water show a splitting of the gas-phase energy levels associated with the 1e(1g)(π), 2e(2g), and 2e(1u) orbitals upon hydration. Lifting of the orbitals degeneracy and redshift of the outer valence bands is related to symmetry breaking of the benzene structure in solution and polarization effects from the surrounding water molecules.     

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.     

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.     

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...