Strong,Thermally Superinsulating Biopolymer–Silica Aerogel Hybrids by Cogelation of Silicic Acid with Pectin

Silica aerogels are excellent thermal insulators, but their brittle nature has prevented widespread application. To overcome these mechanical limitations, silica–biopolymer hybrids are a promising alternative. A one‐pot process to monolithic, superinsulating pectin–silica hybrid aerogels is presented. Their structural and physical properties can be tuned by adjusting the gelation pH and pectin concentration. Hybrid aerogels made at pH 1.5 exhibit minimal dust release and vastly improved mechanical properties while remaining excellent thermal insulators. The change in the mechanical properties is directly linked to the observed “neck‐free” nanoscale network structure with thicker struts. Such a design is superior to “neck‐limited”, classical inorganic aerogels. This new class of materials opens up new perspectives for novel silica–biopolymer nanocomposite aerogels.     

Asymmetric catalysis,CIII: EnantioselectiveMichael addition of 1,3-dicarbonyl compounds to conjugated nitroalkenes

Summary Optically activeMichael adducts were synthesized by addition of 1,3-dicarbonyl compounds to conjugated nitroalkenes. Good chemical yields were obtained for nitroalkenes stabilized by an aromatic substituent without any further substituents at the double bond. Acetylacetone and methyl-2,3-dihydro-1-oxo-1H-indene-2-carboxylate were used asMichael donors and four cinchona alkaloids as chiral base catalysts. Enantiomeric excess determinations were performed by¹H NMR spectroscopy in the presence of thePirkle alcohol and by HPLC on chiral stationary phases. A correlation between the relative configuration of the prevailing isomer of theMichael adduct and the catalysts was established.

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Asymmetrische Katalyse, 103. Mitt.: EnantioselektiveMichael-Addition von 1,3-Dicarbonylverbindungen an konjugierte Nitroalkene

Zusammenfassung Optisch aktiveMichael-Addukte werden durch die Addition von 1,3-Dicarbonylverbindungen an konjugierte Nitroalkene synthetisiert. Gute chemische Ausbeuten werden für durch aromatische Substituenten stabilisierte Nitroalkene ohne weitere Substituenten an der Doppelbindung erreicht. Acetylaceton und 2,3-Dihydro-1-oxo-1H-inden-2-carbonsäuremethylester werden alsMichael-Donoren und vier Cinchona-Alkaloide als chirale basische Katalysatoren verwendet. Die Bestimmung des Enantiomerenüberschusses wird mittels¹H-NMR-Spektroskopie in Gegenwart vonPirkle-Alkohol und HPLC an chiralen stationären Phasen durchgeführt. Eine Korrelation zwischen der relativen Konfiguration der Vorzugsisomeren derMichael-Addukte und den Katalysatoren wurde hergestellt.

     

Multielement (H,C, N,O, S) stable isotope characteristics of lamb meat from different Italian regions

The study focuses on the ²H/H, ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O and ³⁴S/³²S values of defatted dry matter (DFDM) and on the ²H/H, ¹³C/¹²C and ¹⁸O/¹⁶O values of the fat fraction of meat samples from various lamb types reared in seven Italian regions, following different feeding regimes (forage, concentrate, milk). The ¹³C/¹²C (r = 0.922), ²H/H (r = 0.577) and ¹⁸O/¹⁶O (r = 0.449) values of fat and DFDM are significantly correlated, the fat values being significantly lower for C and H and higher for O than for DFDM values and the differences between the two fractions not being constant for different lamb types. The feeding regime significantly affected the ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O and ²H/H of fat. The DFDM ²H/H, and ¹⁸O/¹⁶O values, excluding an outlier, are significantly correlated with the corresponding values in meteoric waters, thus allowing us to trace the variability of geoclimatic factors. ¹⁵N/¹⁴N is influenced by pedoclimatic conditions, whereas ³⁴S/³²S is influenced by the sea spray effect and the surface geology of the provenance area. By applying stepwise linear discriminant analysis only the ²H/H of fat was found not to be significant and 97.7% of the samples were correctly assigned to the lamb type and more than 90% cross‐validated. With the feeding regime, 97.7% of the samples were both correctly assigned and cross‐validated using a predictive model including ¹³C/¹²C, ¹⁵N/¹⁴N, ¹⁸O/¹⁶O, ³⁴S/³²S of DFDM and ¹⁸O/¹⁶O of fat. Copyright © 2009 John Wiley & Sons, Ltd.     

Enzymatic synthesis and chromatographic purification of lignan glucuronides

Enterolactone, enterodiol and secoisolariciresinol were conjugated with glucuronic acid by solubilized rabbit liver microsomal UDP-glucuronyltrasnferase. The monoglucuronide conjugate of all three substrates was formed and its identity confirmed by nuclear magnetic resonance (NMR) spectroscopy. Analytical high pressure liquid chromatography (HPLC) and NMR spectroscopy indicated conjugation with glucuronic acid to occur at several positions in the molecule. The enzymatic conjugation was monitored by analytical capillary isotachophoresis (ITP). The Km-values for enterlactone, enterodiol, and secoisolariciresinol were calculated to be 0.30, 0.23, and 0.22 mmol/l respectively.     

Zur Kenntnis der Netzhautstoffe

Ohne ZusammenfassungDie vorstehende Arbeit wurde seitens der Akademie der Wissenschaften in Wien durch Gewährung einer Subvention aus den Mitteln derZach-Stiftung gefördert. Wir gestatten uns auch an dieser Stelle unseren ergebensten Dank hiefür zum Ausdruck zu bringen.Auch der I. Gr. Farbenindustrie A. G., Leverkusen am Rhein (bzw. Vedepha, Wien) sind wir für die liebenswürdige Überlassung von Cautan (Bayer) zu Dank verpflichtet.     

Trends in solid-state NMR spectroscopy and their relevance for bioanalytics

Based on continuous methodical advances and developments, solid-state NMR spectroscopy has become a powerful tool for the investigation of various materials, including polymers, glasses, zeolites, fullerenes, and many others. During the past decade, solid-state NMR spectroscopy also found increasing interest for the study of biomolecules. For example, membrane proteins reconstituted into lipid environments such as bilayers or vesicles, protein aggregates such as amyloid fibrils, as well as carbohydrates can now be studied by solid-state NMR spectroscopy. This review briefly introduces the principles of solid-state NMR spectroscopy and highlights novel methodical trends. Selected applications demonstrate the possibilities of solid-state NMR spectroscopy as a valuable bioanalytical tool.     

The global version of the gyrokinetic turbulence code GENE

The understanding and prediction of transport due to plasma microturbulence is a key open problem in modern plasma physics, and a grand challenge for fusion energy research. Ab initio simulations of such small-scale, low-frequency turbulence are to be based on the gyrokinetic equations, a set of nonlinear integro-differential equations in reduced (five-dimensional) phase space. In the present paper, the extension of the well-established and widely used gyrokinetic code GENE [F. Jenko, W. Dorland, M. Kotschenreuther, B.N. Rogers, Electron temperature gradient driven turbulence, Phys. Plasmas 7 (2000) 1904–1910] from a radially local to a radially global (nonlocal) version is described. The necessary modifications of both the basic equations and the employed numerical methods are detailed, including, e.g., the change from spectral methods to finite difference and interpolation techniques in the radial direction and the implementation of sources and sinks. In addition, code verification studies and benchmarks are presented.