High-throughput mass spectrometry: the mechanism of sudan azo dye fragmentation by ESI tandem mass spectrometry and extensive deuterium labeling experiments

The investigation of the gas-phase chemistry of azo compounds by mass spectrometry dates back to the introduction of this peculiar research field into the armory of physical organic chemistry tools. The mechanism of the fragmentation of the azo double bond from the protonated precursor is discussed with reference to the behavior of deuterium-labeled reference compounds. The investigated molecules belong to the sudan family and the results can be used for the detection of these potential carcinogenic compounds in different matrices by means of the isotope dilution method.     

Poly(Styrene Sulfonate)/Poly(Allylamine Hydrochloride) Encapsulation of TiO<Subscript>2</Subscript> Nanoparticles Boosts Their Toxic and Repellent Activity Against Zika Virus Mosquito Vectors

Green fabricated nanoparticles often need to be encapsulated and stabilized, to ensure uniform dispersion in the aquatic environment and relevant larvicidal activity over time. However, recent research showed that nanoencapsulation processes led to a reduction of nanoparticle larvicidal efficacy. We used an extract of Argemone mexicana to reduce TiO₂ nanoparticles, which were then capped with PSS/PAH (poly(styrene sulfonate)/poly(allylamine hydrochloride)). The toxic and repellent potential of the nanoparticles were compared to elucidate their potential effects against the Zika virus vector Aedes aegypti. Nanoparticles were characterized by biophysical methods including UV–Vis, EDX and FTIR spectroscopy, SEM, TEM, XRD and DLS analyses. In larvicidal and pupicidal experiments, TiO₂ nanoparticles achieved LC₉₀ values from 41.648 (larva I), to 71.74 ppm (pupa). Nanoencapsulated TiO₂ achieved LC₉₀ values from 39.16 (I), to 69.12 ppm (pupa). In adulticidal experiments, LC₉₀ of TiO₂ nanoparticles on Ae. aegypti was 10.31 ppm, while LC₉₀ of nanoencapsulated TiO₂ was 9.54 ppm. At 10 ppm, the repellency towards Ae. aegypti was 80.43% for TiO₂ nanoparticles, and 88.04% for nanoencapsulated TiO₂. This research firstly highlighted the promising potential of PSS/PAH encapsulation, leading to the production of highly effective titania nanostructures, if compared to titania nanoparticles synthesized with eco-friendly routes without further stabilization.     

Influence of composition on properties of nylon 6/EVOH blends

In this work, the relationships between composition and properties of Ny6/EVOH system were examined by means of several techniques and the results were interpreted in terms of level of compatibility. Blends of different ratio of Ny6 and EVOH have been processed in a laboratory‐based film blowing extrusion apparatus. Rheological measurements, FTIR and morphological analysis, and thermal and mechanical properties were carried out. Peculiar rheological, thermal, and mechanical behaviors were observed for the blend containing 25% by weight of EVOH. At this composition, FTIR analysis has pointed out that a minimum in molecular motion is achieved as a consequence of a maximum interaction of the polar groups (amide groups of Ny6 and hydroxyl groups of EVOH) involved. Moreover, gas permeability measurements on the blown films have been performed at T = 30°C. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2445–2455, 1999     

Synthesis and biological activity of 1-, 2- or 3-Substituted benzothieno-[2,3-d]triazole derivatives structurally related to trazodone

A series of new 1-, 2- and 3-piperazinylbenzothieno[2,3-d]triazole derivatives structurally related to Trazodone were prepared and tested for their antiserotonergic, antiadrenergic and antihistaminergic in vitro activities together with their analgesic in vivo activity by using Trazodone as the reference compound.     

Triorganotin(IV) derivatives of 7-amino-2-(methylthio)[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylic acid. Synthesis, spectroscopic characterization, in vitro antimicrobial activity and X-ray crystallography

Triorganotin(IV) complexes of the 7-amino-2-(methylthio)[1,2,4]triazolo[1,5-a]pyrimidine-6-carboxylic acid (HL), Me₃SnL(H₂O), (1), [n-Bu₃SnL]₂(H₂O), (2), Ph₃SnL(MeOH), (3), were synthesized by reacting the amino acid with organotin(IV) hydroxides or oxides in refluxing methanol. The complexes have been characterized by elemental analysis, ¹H, ¹³C and ¹¹⁹Sn NMR, IR, Raman and ¹¹⁹Sn Mössbauer spectroscopic techniques. Single crystal X-ray diffraction data were obtained for compounds (2) and (3). Ph₃SnL(MeOH) presents a trigonal bipyramidal structure with the organic groups on the equatorial plane and the axial positions occupied by a ligand molecule, coordinated to tin through the carboxylate, and a solvent molecule, MeOH. A similar structure is proposed for Me₃SnL(H₂O) on the basis of analytical and spectroscopic data. The tributyltin(IV) derivative, [n-Bu₃SnL]₂(H₂O), is characterized by two different tin sites with similar tbp geometry featured by butyl groups on the equatorial plane. Sn(1) and Sn(2) atoms are axially bridged by a ligand molecule binding through the N(4) and the carboxylate group; the two coordination spheres are saturated by another ligand molecule, binding the metal through the carboxylate group, and a water molecule, respectively. Antimicrobial tests on compounds 1 and 2 showed in vitro activity against Gram-positive bacteria.     

Asymptotics for eigenvalues of the Laplacian in higher dimensional periodically perforated domains

This paper considers the periodic spectral problem associated with the Laplace operator written in \mathbbR^N{\mathbb{R}^N} (N = 3, 4, 5) periodically perforated by balls, and with homogeneous Dirichlet condition on the boundary of holes. We give an asymptotic expansion for all simple eigenvalues as the size of holes goes to zero. As an application of this result, we use Bloch waves to find the classical strange term in homogenization theory, as the size of holes goes to zero faster than the microstructure period.     

Antibacterial activity of tetraaryl-porphyrin photosensitizers: an in vitro study on Gram negative and Gram positive bacteria

BACKGROUND: Photodynamic therapy exploits visible light and photosensitizers to inactivate cells and this methodology is currently used for the treatment of several types of malignancy. Although various tumours are successfully treated with PSs and light, the application on microorganisms (photodynamic antimicrobial chemotherapy) has not yet found specific medical applications and still remains an open field of fundamental research. PURPOSE: The assessment of the effect of a panel of seven tetraaryl-porphyrins, two commercial (PS 1 and 2) and five synthetic (PS 3-7) in in vitro experiments against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. METHODS: Three of the new photosensitizers (PS 3, 4 and 5) are tetracationic porphyrins and were prepared by N-alkylation of 5,10,15,20-tetra-4-pyridylporphyrin with a large excess of different benzyl chlorides; compound 7 is a dicationic porphyrin and was obtained in a similar way using a lower excess of 4-methoxybenzyl chloride. The neutral porphyrin (PS 6) was previously described. Dose-response curves were obtained titrating the survivors of cell suspensions (10(8)cfu/ml) exposed to the PSs and irradiated with visible light (total fluence rate 266 J/cm2). RESULTS: The non ionic porphyrin 6 was the least active PS against all the tested bacteria. Cationic PSs 3, 4, 5 and 7 were more active than the commercial 1 and 2. The Gram positive S. aureus was more sensitive to all the PSs than the Gram negative E. coli and P. aeruginosa, the latter being the more resistant one. Compound 7 was found particularly efficient against P. aeruginosa, causing a 7 log units reduction of survivors at a concentration of 8 microM. CONCLUSIONS: The reported results confirm that the presence of positively charged groups on porphyrin frame is fundamental for PSs antibacterial activity, however our data suggest that a moderate degree of lipophilicity, achievable by the introduction of aromatic hydrocarbon side chains on the pyridyl moieties, may improve PSs efficiency. Furthermore dicationic porphyrin 7 seems to be more efficient than the corresponding tetracationic derivatives thus emphasizing an interesting feature involved in the PSs activity.     

A modified Lagrange–Galerkin method for a fluid-rigid system with discontinuous density

In this paper, we propose a new characteristics method for the discretization of the two dimensional fluid-rigid body problem in the case where the densities of the fluid and the solid are different. The method is based on a global weak formulation involving only terms defined on the whole fluid-rigid domain. To take into account the material derivative, we construct a special characteristic function which maps the approximate rigid body at the (k?+?1)-th discrete time level into the approximate rigid body at k-th time. Convergence results are proved for both semi-discrete and fully-discrete schemes.     

Cytotoxic performances of new anionic cyclometalated Pt(II) complexes bearing chelated O^O ligands

The in vitro biological activity towards the MDA-MB-231 triple-negative breast cancer cell line of two different series of anionic Pt(II) organometallic complexes was tested. For the first time, cytotoxic activity of anionic Pt(II) complexes has been observed. The anionic compounds of general formula NBu₄[(C^N)Pt(O^O)], where (C^N) represents the cyclometalated form of 2-phenylpyridine (H(PhPy)), 2-thienylpyridine (H(Thpy)) or 2-benzo[h]quinoline (H(Bzq)), feature two different (O^O) chelated ligands: tetrabromocatechol [BrCat]²⁻ ( 1 – 3 ) or alizarine [Aliz]²⁻ ( 4 – 6 ). Complexes 1 – 6 displayed a significant cytotoxic effect against the studied cell line (IC₅₀ range of 1.9–52.8 μM). For BrCat-containing complexes 1 – 3 , the biological activity was independent of the nature of the coordinated (C^N) ligand. In contrast, in the case of 4 – 6 , the cytotoxicity (significantly high for 4 ) was concomitantly induced by the presence of either the PhPy or the [Aliz]²⁻ ligand. Since complexes 1–6 are emissive in solution, the potential use of 4 as a theranostic agent was investigated using confocal analysis. The fluorescence signal from MDA-MB-231 cells incubated with 4 indicated the localization of the compound into the cytosol region.