Preparation,characterization and catalytic studies of V<Subscript>2</Subscript>O<Subscript>5</Subscript>–SiO<Subscript>2</Subscript> xerogel composite

In this work, we report the synthesis, characterization and catalytic properties of a vanadium oxide–silicon oxide composite xerogel prepared by a soft chemistry approach. In order to obtain such material, we submitted a vanadium pentoxide gel previously synthesized via protonation of metavanadate species to an “in situ” progressive polycondensation into silica gel. The material has been characterized by X-ray diffraction, infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Further, the catalytic activity of this material was evaluated for the epoxidation of styrene and cyclooctene using iodosylbenzene, hydrogen peroxide and m-chloroperbenzoic acid as the oxidizing agent.     

Voltammetric Determination of Chloride Ion in Automotive Fuel Ethanol

Cathodic stripping voltammetry with a hanging mercury drop electrode was used in this study to determine chloride ions in automotive fuel ethanol. Choosing the correct stripping voltammetric technique, the correct choice of deposition potential and time provided well defined voltammetric waves with good repeatability and relatively small errors, with a determination limit of 0.13 mg L^?1, for only 10 s of deposition time, with better sensitivity and repeatability than the normalized method, as well as consumed less volume of the sample, being suitable for routine analysis.     

Electron detachment dissociation of dermatan sulfate oligosaccharides

The structural characterization of glycosaminoglycans (GAG) oligosaccharides has been a long-standing challenge in the field of mass spectrometry. In this work, we present the application of electron detachment dissociation (EDD) Fourier transform mass spectrometry to the analysis of dermatan sulfate (DS) oligosaccharides up to 10 residues long. The EDD mass spectra of DS oligosaccharides were compared with their infrared multiphoton dissociation (IRMPD) mass spectra. EDD produces more abundant fragmentation than IRMPD with far less loss of SO3 from labile sulfate modifications. EDD cleaves all glycosidic bonds, yielding both conventional glycosidic bond fragmentation as well as satellite peaks resulting from the additional loss of 1 or 2 hydrogen atoms. EDD also yields more cross-ring fragmentation than IRMPD. For EDD, abundant cross-ring fragmentation in the form of A- and X-ions is observed, with 1,5Xn cleavages occurring for all IdoA residues and many of the GalNAc4S residues, except at the reducing and nonreducing ends. In contrast, IRMPD produces only A-type cross-ring fragmentation for long oligosaccharides (dp6-dp10). As all the structurally informative fragment ions observed by IRMPD appear as a subset of the peaks found in the EDD mass spectrum, EDD shows great potential for the characterization of GAG oligosaccharides using a single tandem mass spectrometry experiment.     

The effect of the synthesis method on the parameters of pore structure and selectivity of ferrocyanide sorbents based on natural minerals

Ferrocyanide sorbents were obtained via thin-layer and surface modification of natural clinoptilolite and marl. The effect of modification method on surface characteristics of these sorbents and their selectivity for cesium was studied. It was shown that the modification resulted in an increase of selectivity of modified ferrocyanide sorbents to cesium as compared with the natural clinoptilolite in presence of Na⁺, as well as in an increase of cesium distribution coefficients in presence of K⁺. The nickel–potassium ferrocyanide based on the clinoptilolite showed the highest selectivity for cesium at sodium concentrations of 10^?4—2 mol L^?1: cesium distribution coefficient was lg K _d = 4.5 ± 0.4 L kg^?1 and cesium/sodium separation factor was α(Cs/Na) = 250. In the presence of NH₄ ⁺, all modified sorbents showed approximately equal selectivity for ¹³⁷Cs. Probable applications of the sorbents were suggested.     

Diethyl oxalacetate sodium salt as a reagent to obtain functionalized spiro[indoline-3,4′-pyrano[2,3-c]pyrazoles]

An efficient one-pot procedure for the synthesis of ethyl 6′-amino-5′-cyano-2-oxo-2′H-spiro[indoline-3,4′-pyrano[2,3-c]pyrazole]-3′-carboxylates in moderate to high yields is described.     

Endogenous Retinoic Acid Required to Maintain the Epidermis Following Ultraviolet Light Exposure in SKH‐1 Hairless Mice

Ultraviolet light B (UVB) exposure induces cutaneous squamous cell carcinoma (cSCC), one of the most prevalent human cancers. Reoccurrence of cSCC in high‐risk patients is prevented by oral retinoids. But oral retinoid treatment causes significant side effects; and patients develop retinoid resistance. Exactly how retinoids prevent UVB‐induced cSCC is currently not well understood. Retinoid resistance blocks mechanistic studies in the leading mouse model of cSCC, the UVB‐exposed SKH‐1 hairless mouse. To begin to understand the role of retinoids in UVB‐induced cSCC we first examined the localization pattern of key retinoid metabolism proteins by immunohistochemistry 48 h after UVB treatment of female SKH‐1 mice. We next inhibited retinoic acid (RA) synthesis immediately after UVB exposure. Acute UVB increased RA synthesis, signaling and degradation proteins in the stratum granulosum. Some of these proteins changed their localization; while other proteins just increased in intensity. In contrast, acute UVB reduced the retinoid storage protein lectin:retinol acyltransferase (LRAT) in the epidermis. Inhibiting RA synthesis disrupted the epidermis and impaired differentiation. These data suggest that repair of the epidermis after acute UVB exposure requires endogenous RA synthesis.     

Influence of Trans Fat on Skin Damage in First‐Generation Rats Exposed to UV Radiation

The influence of trans fatty acids (TFA) on lipid profile, oxidative damage and mitochondrial function in the skin of rats exposed to ultraviolet radiation (UVR) was assessed. The first‐generation offspring of female Wistar rats supplemented from pregnancy with either soybean oil (C‐SO, rich in n–6 FA; control group) or hydrogenated vegetable fat (HVF, rich in TFA) were continued with the same supplements until adulthood, when half of each group was exposed to UVR for 12 weeks. The HVF group showed higher TFA cutaneous incorporation, increased protein carbonyl (PC) levels, decreased functionality of mitochondrial enzymes and antioxidant defenses of the skin. After UVR, the HVF group showed increased skin thickness and reactive species (RS) generation, with decreased skin antioxidant defenses. RS generation was positively correlated with skin thickness, wrinkles and PC levels. Once incorporated to skin, TFA make it more susceptible to developing UVR‐induced disorders.     

Recent Progress toward the Introduction of Functionalized Difluoromethylated Building Blocks onto C(sp2) and C(sp) Centers

Fluorine chemistry is a field undergoing tremendous expansion. Although much attention has been paid to the introduction of the fluorine atom and the CF₃ group, less interest has been devoted to the introduction of functionalized fluorinated building blocks, in sharp contrast with the high versatility of the fluorinated products. In this Minireview, the most relevant methods for the introduction of difluoromethylated building blocks are summarized. Access to difluoromethylated arenes, alkenes, and alkynes is highlighted and special attention is paid to explanation of the reaction mechanism.     

Non‐Uniform Sampling and J‐UNIO Automation for Efficient Protein NMR Structure Determination

High‐resolution structure determination of small proteins in solution is one of the big assets of NMR spectroscopy in structural biology. Improvements in the efficiency of NMR structure determination by advances in NMR experiments and automation of data handling therefore attracts continued interest. Here, non‐uniform sampling (NUS) of 3D heteronuclear‐resolved [¹H,¹H]‐NOESY data yielded two‐ to three‐fold savings of instrument time for structure determinations of soluble proteins. With the 152‐residue protein NP_372339.1 from Staphylococcus aureus and the 71‐residue protein NP_346341.1 from Streptococcus pneumonia we show that high‐quality structures can be obtained with NUS NMR data, which are equally well amenable to robust automated analysis as the corresponding uniformly sampled data.