Ultra‐Performance Liquid Chromatography‐Mass Spectrometry Analysis of Free and Esterified Oxygenated Derivatives from Docosahexaenoic Acid in Rat Brain

Docosahexaenoic acid (DHA), a prominent long‐chain fatty acid of the omega‐3 family, is present at high amount in brain tissues, especially in membrane phospholipids. This polyunsaturated fatty acid is the precursor of various oxygenated lipid mediators involved in diverse physiological and pathophysiological processes. Characterization of DHA‐oxygenated metabolites is therefore crucial for better understanding the biological roles of DHA. In this study, we identified and measured, by ultrahigh‐performance liquid chromatography coupled with tandem mass spectrometry, a number of oxygenated products derived from DHA in exsanguinated and nonexsanguinated brains. These metabolites were found both in free form and esterified in phospholipids. Interestingly, both (R)‐ and (S)‐monohydroxylated fatty acid stereoisomers were observed free and esterified in phospholipids. Monohydroxylated metabolites were the main derivatives; however, measurable amounts of dihydroxylated products such as protectin DX were detected. Moreover, exsanguination allowed discriminating brain oxygenated metabolites from those generated in blood. These results obtained in healthy rats allowed an overview on the brain oxygenated metabolism of DHA, which deserves further research in pathophysiological conditions, especially in neurodegenerative diseases.     

Layered Simple Hydroxides Functionalized by Fluorene‐Phosphonic Acids: Synthesis,Interface Theoretical Insights,and Magnetoelectric Effect

Copper‐ and cobalt‐based layered simple hydroxides (LSH) are successfully functionalized by a series of fluorene mono‐ and diphosphonic acids, using anionic exchange reactions and a preintercalation strategy. The lateral functionalization of the fluorene moieties has only little impact on the overall structure of the obtained layered hybrid materials but it influences the organization of the molecules within the interlamellar spacing. For bulky fluorene (9,9‐dioctyl derivative), luminescence is preserved when inserted into copper and cobalt hydroxydes, whereas it is completely quenched for the other fluorenes. Detailed characterization of the internal structure and chemical bonding properties for copper‐ and cobalt‐based hybrids is performed via ancillary experimental techniques. For the copper‐based LSH class, for which more elusive findings are found, first‐principles molecular dynamics simulations unravel the fundamental stabilizing role of the H‐bonding network promoted within the local environments of the fluorene mono‐ and diphosphonic acids. The cobalt series of compounds constitute a new class of hybrid magnets, with ordering temperatures ranging from 11.8 to 17.8 K and show a clear magnetoelectric effect. This effect appears above a threshold magnetic field, which is null below the magnetic ordering temperature, and it persists in the paramagnetic regime till about 110 K.     

Structural Insights into the Recognition of N2‐Aryl‐ and C8‐Aryl DNA Lesions by the Repair Protein XPA/Rad14

Aromatic amines are strongly carcinogenic. They are activated in the liver to give reactive nitrenium ions that react with nucleobases within the DNA duplex. The reaction occurs predominantly at the C8 position of the dG base, thereby giving C8‐acetyl‐aryl‐ or C8‐aryl‐dG adducts in an electrophilic aromatic substitution reaction. Alternatively, reaction with the exocyclic 2‐NH₂ group is observed. Although the C8 adducts retain base‐pairing properties, base pairing is strongly compromised in the case of the N² adducts. Here we show crystal structures of two DNA lesions, N²‐acetylnaphthyl‐dG and C8‐fluorenyl‐dG, within a DNA duplex recognized by the repair protein Rad14. The structures confirm that two molecules of the repair protein recognize the lesion and induce a 72 or 78° kink at the site of the damage. Importantly, the same overall kinked structure is induced by binding of the repair proteins, although the structurally different lesions result in distinct stacking interactions of the lesions within the duplex. The results suggest that the repair protein XPA/Rad14 is a sensor that recognizes flexibility. The protein converts the information that structurally different lesions are present in the duplex into a unifying sharply kinked recognition motif.     

A zeolite family with chiral and achiral structures built from the same building layer

Porosity and chirality are two of the most important properties for materials in the chemical and pharmaceutical industry. Inorganic microporous materials such as zeolites have been widely used in ion-exchange, selective sorption/separation and catalytic processes. The pore size and shape in zeolites play important roles for specific applications. Chiral inorganic microporous materials are particularly desirable with respect to their possible use in enantioselective sorption, separation and catalysis. At present, among the 179 zeolite framework types reported, only three exhibit chiral frameworks. Synthesizing enantiopure, porous tetrahedral framework structures represents a great challenge for chemists. Here, we report the silicogermanates SU-32 (polymorph A), SU-15 (polymorph B) (SU, Stockholm University) and a hypothetical polymorph C, all built by different stacking of a novel building layer. Whereas polymorphs B and C are achiral, each crystal of polymorph A exhibits only one hand and has an intrinsically chiral zeolite structure. SU-15 and SU-32 are thermally stable on calcination.     

Identification and Optimization of Microbial Attractants for <Emphasis Type="Italic">Philornis downsi</Emphasis>, an Invasive Fly Parasitic on Galapagos Birds

We investigated the role of olfactory cues from actively fermenting yeast (Saccharomyces cerevisiae) in attraction of adult Philornis downsi and identified two synergistically attractive yeast volatiles. Larvae of this invasive fly parasitize the hatchlings of passerines and threaten the Galapagos avifauna. Gas chromatography coupled with electroantennographic detection (GC-EAD), coupled gas chromatography-mass spectrometry (GC-MS), and field trapping experiments were used to identify volatile compounds from a yeast-sugar solution. EAD responses were consistently elicited by 14 yeast volatiles. In a series of field trapping experiments, a mixture of the 14 EAD-active compounds was similarly attractive to P. downsi when compared to the yeast-sugar solution, and we found that acetic acid and ethanol were essential for attraction. A mixture of 0.03 % acetic acid and 3 % ethanol was as attractive as the 14-component blend, but was not as attractive as the yeast-sugar solution. Philornis downsi showed positive and negative dose-responses to acetic acid in the ranges of 0.01 ~ 0.3 % and 0.3 ~ 9 %, respectively. Further optimization showed that the mixture of 1 % acetic acid and 3 % ethanol was as attractive as the yeast-sugar solution. Both mixtures of acetic acid and ethanol were more selective than the yeast-sugar solution in terms of non-target moths and Polistes versicolor wasps captured. These results indicate that acetic acid and ethanol produced by yeasts are crucial for P. downsi attraction to fermented materials on which they feed as adults and can be used to manage this invasive fly in Galapagos.     

Sparse decomposition and modeling of anatomical shape variation

Recent advances in statistics have spawned powerful methods for regression and data decomposition that promote sparsity, a property that facilitates interpretation of the results. Sparse models use a small subset of the available variables and may perform as well or better than their full counterparts if constructed carefully. In most medical applications, models are required to have both good statistical performance and a relevant clinical interpretation to be of value. Morphometry of the corpus callosum is one illustrative example. This paper presents a method for relating spatial features to clinical outcome data. A set of parsimonious variables is extracted using sparse principal component analysis, producing simple yet characteristic features. The relation of these variables with clinical data is then established using a regression model. The result may be visualized as patterns of anatomical variation related to clinical outcome. In the present application, landmark-based shape data of the corpus callosum is analyzed in relation to age, gender, and clinical tests of walking speed and verbal fluency. To put the data-driven sparse principal component method into perspective, we consider two alternative techniques, one where features are derived using a model-based wavelet approach, and one where the original variables are regressed directly on the outcome.     

Greffage de molécules à la surface du silicium par voie électrochimique

The hydrogentated surface of silicon exhibits remarkable properties, but poor resistance to oxidation. To improve its stability, surface hydrogen has been replaced by several organic groups. Such grafting can be carried out chemically by a multi-step reaction scheme. However, an electrochemical approach allows direct reaction with the hydrogenated surface. The porous-silicon surface has been partially methoxylated by a controlled anodic dissolution. If has also been methylated using a non-destructive anodic process, with a yield of 80%, limited only by steric hindrance. The methylated surface of porous silicon exhibits a stability against oxidation increased by an order of magnitude.