Origin of photoactivity of nitrogen-doped titanium dioxide under visible light

Nitrogen-doped titanium dioxide (N-TiO2), a photocatalytic material active in visible light, has been investigated by a combined experimental and theoretical approach. The material contains single-atom nitrogen impurities that form either diamagnetic (Nb-) or paramagnetic (Nb*) bulk centers. Both types of Nb centers give rise to localized states in the band gap of the oxide. The relative abundance of these species depends on the oxidation state of the solid, as, upon reduction, electron transfer from Ti3+ ions to Nb* results in the formation of Ti4+ and Nb-. EPR spectra measured under irradiation show that Nb centers are responsible for visible light absorption with promotion of electrons from the band gap localized states to the conduction band or to surface-adsorbed electron scavengers. These results provide a characterization of the electronic states associated with N impurities in TiO2 and, for the first time, a picture of the processes occurring in the solid under irradiation with visible light.     

Solvent-free, heterogeneous photooxygenation of hydrocarbons by hyflon membranes embedding a fluorous-tagged decatungstate

Hybrid fluoropolymeric membranes with 25% loading of the fluorous-tagged (RfN)4W10O32 effect the solvent-free photooxygenation of benzylic C-H bonds with up to 6100 TONs in 4 hours.     

Temperature effects upon aqueous micellar-assisted decarboxylation of 6-nitrobenzisoxazole-3-carboxylate and its 5-methyl derivative

An investigation of temperature effects upon first-order rate constants in the micellar pseudophase for decarboxylation of 6-nitrobenzisoxazole-3-carboxylate (6-NBIC) and its 5-methyl derivative (6-NBIC-5-Me) was carried out. Surfactants used were cationic cetyltrialkylammonium bromide with alkyl = methyl (CTABr), ethyl (CTEABr), n-propyl (CTPABr), and n-butyl (CTBABr). The investigation shows that micelles speed up reactions by decreasing enthalpies of activation. Increase in head group bulk further speeds reactions still by a small decrease in the enthalpies, for both substrates. Values of DeltaH# and DeltaS# for 6-NBIC in the various surfactants give linear isokinetic plot, with CTBABr as outlier.     

Optimal packet-to-slot assignment in mobile telecommunications

The problem of assigning information packets of different services to time slots of a radio frame is addressed. Packet sizes are divisible, and a maximum time slot to which a packet can be assigned is given. We present a polynomial-time scheduling algorithm maximizing the number of scheduled packets.     

Quantification of Protein “Biomarkers” in Wheat-Based Food Systems: Dealing with Process-Related Issues

Selected food proteins may represent suitable markers for assessing either the presence/absence of specific food ingredients or the type and intensity of food processes. A fundamental step in the quantification of any protein marker is choosing a proper protocol for solubilizing the protein of interest. This step is particularly critical in the case of solid foods and when the protein analyte is prone to undergo intermolecular disulfide exchange reactions with itself or with other protein components in the system as a consequence of process-induced unfolding. In this frame, gluten-based systems represent matrices where a protein network is present and the biomarker proteins may be either linked to other components of the network or trapped into the network itself. The protein biomarkers considered here were wheat gluten toxic sequences for coeliac (QQPFP, R5), wheat germ agglutinin (WGA), and chicken egg ovalbumin (OVA). These proteins were considered here in the frame of three different cases dealing with processes different in nature and severity. Results from individual cases are commented as for: (1) the molecular basis of the observed behavior of the protein; (2) the design of procedure aimed at improving the recovery of the protein biomarker in a form suitable for reliable identification and quantification; (3) a critical analysis of the difficulties associated with the plain transfer of an analytical protocol from one product/process to another. Proper respect for the indications provided by the studies exemplified in this study may prevent coarse errors in assays and vane attempts at estimating the efficacy of a given treatment under a given set of conditions. The cases presented here also indicate that recovery of a protein analyte often does not depend in a linear fashion on the intensity of the applied treatment, so that caution must be exerted when attributing predictive value to the results of a particular study.     

Polyadenylic acid binding on cationic liposomes doped with the non-ionic nucleolipid Lauroyl Uridine

In this work unilamellar liposomes doped with a novel non-ionic 5′-Uridine-head nucleolipid, Lauroyl Uridine (LU), were prepared and characterized for their ability to interact with the polynucleotide polyadenylic acid (poly-A). Vesicles, were made up of the cationic lipid DOTAP (1,2-Dioleoyl-3-Trimethylammonium-Propane), the zwitterionic lipid DOPE (1,2-Dioleoyl-sn-Glycero-3-Phosphoethanolamine), and the novel amphiphile Lauroyl Uridine. The influence of the non-ionic nucleolipid on essential liposomes properties, such as the structure and net charge was first investigated by a comparative analysis performed on the different lipoplex preparations by means of ζ-potential and size measurements. Both structure and net charge of liposomes were shown to be not modified by the presence of the non-ionic nucleolipid.The role of the synthetic lipid inserted as anchor in the liposome bilayer in the condensation process between vesicles and the polynucleotide poly-A was then analyzed by UV–vis, Circular Dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopies. The data presented comparative UV–vis analyses that evidenced the occurrence of staking interactions in the poly-A only in LU containing lipoplexes. CD and NMR studies indicated the presence of H-bonding interaction between Lauroyl Uridine containing vesicles and the polynucleotide poly-A. The results presented in this work support a role for Lauroyl Uridine in A-U molecular recognition, thus, suggesting that cationic liposomes doped with the non-ionic nucleolipid Lauroyl Uridine could represent a model system to study molecular interactions among single stranded polynucleotides and lipid anchor bearing the complementary bases.     

ChemInform Abstract: Ab initio Theory of Point Defects in Oxide Materials: Structure,Properties, Chemical Reactivity

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

ChemInform Abstract: A Route Toward the Generation of Thermally Stable Au Cluster Anions Supported on the MgO Surface.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

A Metal-Free C−H Amination-Based Strategy for N-Amino Indole Synthesis

An oxidative cyclization of electron-rich α-arylhydrazones promoted by phenyliodine bis(trifluoroacetate) (PIFA) has been accomplished. This metal-free, chemoselective transformation allows to obtain synthetically and medicinally important N-amino-1H-indoles, obviating the need for pre-functionalization of substrates.