NH3 and O2 interaction with tetrahedral Ti3+ ions isomorphously substituted in the framework of TiAlPO-5. A combined pulse EPR, pulse ENDOR, UV-Vis and FT-IR study

Continuous Wave (CW), pulse Electron Paramagnetic Resonance (EPR) and pulse Electron Nuclear Double Resonance (ENDOR) spectroscopies, in conjunction with UV-Vis and Infrared (IR) spectroscopies, are used to investigate the chemical reactivity of tetrahedrally coordinated Ti(3+) ions isomorphously substituted in the framework of AlPO-5 towards NH(3) and O(2). The coordination of ammonia to Ti(3+) centres is followed in detail by complementary vibrational and electron magnetic resonance techniques. In particular HYSCORE spectra allow identifying the coordination of two ammonia molecules to Ti(3+) centres resolving the full hyperfine and quadrupole (14)N coupling tensors. The reactivity of the reduced TiAlPO sample towards molecular oxygen is detailed by means of CW-EPR and pulse ENDOR spectroscopy. (17)O(2) is employed, allowing to establish the formation of a "side-on" η(2) O(2)(-)-Ti(4+) electrostatic complex. Pulse ENDOR spectra provide detailed information on the local environment of the formed superoxide radical anion which acts as a paramagnetic probe, providing evidence for Ti-O-Ti oligomeric species.     

The impact of dihydrogen phosphate anions on the excited-state proton transfer of harmane. Effect of β-cyclodextrin on these photoreactions

Photoinduced proton transfer reactions of harmane (1-methyl-9H-pyrido[3,4-b]indole) (HAR) in the presence of a proton donor/acceptor such as dihydrogen phosphate anions in aqueous solution have been studied by stationary and time-resolved fluorescence spectroscopy. The presence of high amounts of dihydrogen phosphate ions modifies the acid/base properties of this alkaloid. Thus, by keeping the pH constant at pH 8.8 and by increasing the amount of NaH(2)PO(4) in the solution, it is possible to reproduce the same spectral profiles as those obtained in high alkaline solutions (pH >12) in the absence of NaH(2)PO(4). Under these conditions, a new fluorescence profile appears at around 520 nm. This result could be related to the results of a recent investigation which suggests that a high intake of phosphates may promote skin tumorigenesis. The presence of β-cyclodextrin (β-CD) avoids the proton transfer reactions in this alkaloid by means the formation of an inclusion complex between β-CD and HAR. The formation of this complex originates a remarkable enhancement of the emission intensity from the neutral form in contrast to the cationic and zwitterionic forms. A new lifetime was obtained at 360 nm (2.5 ns), which was associated with the emission of this inclusion complex. At this wavelength, the fluorescence intensity decay of HAR can be described by a linear combination of two exponentials. From the ratio between the pre-exponential factors, we have obtained a value of K = 501 M for the equilibrium of formation of this complex.     

Spectral measure and approximation of homogenized coefficients

This article deals with the numerical approximation of effective coefficients in stochastic homogenization of discrete linear elliptic equations. The originality of this work is the use of a well-known abstract spectral representation formula to design and analyze effective and computable approximations of the homogenized coefficients. In particular, we show that information on the edge of the spectrum of the generator of the environment viewed by the particle projected on the local drift yields bounds on the approximation error, and conversely. Combined with results by Otto and the first author in low dimension, and results by the second author in high dimension, this allows us to prove that for any dimension d?≥ 2, there exists an explicit numerical strategy to approximate homogenized coefficients which converges at the rate of the central limit theorem.     

Conformational polymorphism of the PrP106-126 peptide in different environments: a molecular dynamics study

Extensive molecular dynamic simulations (approximately 240 ns) have been used to investigate the conformational behavior of PrP106-126 prion peptide in four different environments (water, dimethyl sulfoxide, hexane, and trifluoroethanol) and under both neutral and acidic conditions. The conformational polymorphism of PrP106-126 in solution observed in the simulations supports the role of this fragment in the structural transition of the native to the abnormal form of prion protein in response to changes in the local environmental conditions. The peptide in solution is primarily unstructured. The simulations show an increased presence of helical structure in an apolar solvent, in agreement with the results from circular dichroism spectroscopy. In water solution, beta-sheet elements were observed between residues 108-112 and either residues 115-121 or 121-126. An alpha-beta transition was observed under neutral conditions. In DMSO, the peptide adopted an extended conformation, in agreement with nuclear magnetic resonance experiments.     

Streamlined, asymmetric synthesis of 8,4'-oxyneolignans

Highly direct, modular syntheses of several natural 8,4'-oxyneolignans [(-)-1, (+)-1, (-)-2, and (-)-3] and some related variants [(-)-26, (+)-26, (+)-27, and (-)-28] are reported. Utilizing (S)- or (R)-methyl lactate as the chiral sources, two complementary syn- or anti-oriented routes were designed, encompassing nine and five steps, which were carried out to deliver the targets in an enantiomerically pure form. The embodiment of the two independent aryl and aryloxy moieties onto the lactate frame was performed according to a diversity-oriented protocol from the common precursors, aldehydes 6 and ent-6 for the syn-oriented routes and mesyl esters 19 and ent-19 for the anti-oriented routes. These syntheses set the stage for the generation of a wide and diverse repertoire of 8,4'-oxyneolignan compounds and the broad biological interrogation of its members.     

Multimodal Biomedical Implant with Plasmonic and Simulated Body Temperature Responses

This work presents a novel nanoparticle-based thermosensor implant able to reveal the precise temperature variations along the polymer filaments, as it contracts and expands due to changes in the macroscale local temperature. The multimodal device is able to trace the position and the temperature of a polypropylene mesh, employed in abdominal hernia repair, by combining plasmon resonance and Raman spectroscopy with hydrogel responsive system. The novelty relies on the attachment of the biocompatible nanoparticles, based on gold stabilized by a chitosan-shell, already charged with the Raman reporter (RaR) molecules, to the robust prosthesis, without the need of chemical linkers. The SERS enhanced effect observed is potentiated by the presence of a quite thick layer of the copolymer (poly(N-isopropylacrylamide)-co-poly(acrylamide)) hydrogel. At temperatures above the LCST of PNIPAAm-co-PAAm, the water molecules are expulsed and the hydrogel layer contracts, leaving the RaR molecules more accessible to the Raman source. In vitro studies with fibroblast cells reveal that the functionalized surgical mesh is biocompatible and no toxic substances are leached in the medium. The mesh sensor opens new frontiers to semi-invasive diagnosis and infection prevention in hernia repair by using SERS spectroscopy. It also offers new possibilities to the functionalization of other healthcare products.     

Raman and FTIR imaging of lung tissue: bronchopulmonary sequestration

Bronchopulmonary sequestration (BPS) involves abnormal pulmonary tissue lacking trancheobronchial connection and having a separate vascular supply that arises from the thoracic or abdominal aorta. For the first time, BPS is studied by Raman and Fourier‐transform infrared (FTIR) imaging. Cryosections were mounted on calcium fluoride substrates from tissue samples of two BPS patients. Raman images were collected at a step size of 66–100 µm to assess the whole tissue section, and at a lower step size of 10 µm to resolve details in selected areas. FTIR images were collected at resolutions of 63 and 4 µm per pixel. Data sets were segmented by cluster analyses, and the spectra of each cluster were compared. The spectra revealed higher red blood cell content and lower collagen and lipid content in BPS than in an additional tissue section from the BPS margin. Comparison with previous Raman and FTIR images of congenital cystic adenomatoid malformations (CCAM) and normal lung tissue suggested that the marginal tissue sample of the BPS patient contains CCAM. We conclude that CCAM and BPS are biochemically distinct, which enable the differential diagnosis of lung malformations by specific vibrational spectroscopic fingerprints. Copyright © 2008 John Wiley & Sons, Ltd.     

Crystal and Molekular Structure of Piperidinium-acet-p-Cl-anilide-chloride

Piperidinium-acet-p-Cl-anilide-chloride crystallizes in the triclinic space group P 1 with 2 formula units C₁₃H₁₈ON₂Cl₂ in the unit cell. The lattice constants are a = 10.471 Å, b = 12.545 Å, c = 6.149 Å, α = 72.14°, β = 105.70° and γ = 105.21°. Bond lengths, bond angles and the conformational flexibility were determined by X-ray structure analysis. The crystal structure contains dimeres consisting of drug molecules connected by hydrogen bonds.     

Blends Based on Polystyrene and Statistical Aromatic Copolycarbonates

The compatibility of polystyrene (PS) with aromatic copolycarbonates containing bisphenol A (BPA) and tetramethyl bisphenol A (TMBPA) was investigated. The simple prevision scheme developed by Sonja Krause was employed to evaluate the effect of the copolymer molecular structure on the miscibility with polystyrene. These prevision data were used to select copolycarbonates of potential interest. Statistical copolycarbonates (CPC) containing different BPA/TMBPA molar ratios were synthesised by polycondensation reaction between a mixture of the two monomers and phosgene. PS/polycarbonates blends, prepared by casting from chloroform solution, were studied with differential scanning calorimetry and optical microscopy to evaluate the components compatibility, which increases with the TMBPA copolymer content.