Configurational entropy of a finite number of dumbbells close to a wall

The European Physical Journal E - Many types of motile cells perform durotaxis, namely directed migration following gradients of substrate stiffness. Recent experiments have revealed that cell...     

Highly dispersed palladium nanoparticles on mesocellular foam: an efficient and recyclable heterogeneous catalyst for alcohol oxidation

Palladium nanoparticles immobilized on amino-functionalized mesocellular foam constitute an efficient catalyst for the aerobic oxidation of primary and secondary alcohols to their corresponding carbonyl compounds in high to excellent yields. An exceptionally high TON of 365?000 was reached for the oxidation of 1-phenylethanol under solvent-free reaction conditions. The catalyst can be recycled many times with retained activity as shown by the identical rate curves of the first and fifth runs.     

Quadracyclic adenine: a non-perturbing fluorescent adenine analogue

Fluorescent-base analogues (FBAs) comprise a group of increasingly important molecules for the investigation of nucleic acid structure and dynamics as well as of interactions between nucleic acids and other molecules. Here, we report on the synthesis, detailed spectroscopic characterisation and base-pairing properties of a new environment-sensitive fluorescent adenine analogue, quadracyclic adenine (qA). After developing an efficient route of synthesis for the phosphoramidite of qA it was incorporated into DNA in high yield by using standard solid-phase synthesis procedures. In DNA qA serves as an adenine analogue that preserves the B-form and, in contrast to most currently available FBAs, maintains or even increases the stability of the duplex. We demonstrate that, unlike fluorescent adenine analogues, such as the most commonly used one, 2-aminopurine, and the recently developed triazole adenine, qA shows highly specific base-pairing with thymine. Moreover, qA has an absorption band outside the absorption of the natural nucleobases (>300?nm) and can thus be selectively excited. Upon excitation the qA monomer displays a fluorescence quantum yield of 6.8?% with an emission maximum at 456?nm. More importantly, upon incorporation into DNA the fluorescence of qA is significantly less quenched than most FBAs. This results in quantum yields that in some sequences reach values that are up to fourfold higher than maximum values reported for 2-aminopurine. To facilitate future utilisation of qA in biochemical and biophysical studies we investigated its fluorescence properties in greater detail and resolved its absorption band outside the DNA absorption region into distinct transition dipole moments. In conclusion, the unique combination of properties of qA make it a promising alternative to current fluorescent adenine analogues for future detailed studies of nucleic acid-containing systems.     

The total synthesis of (-)-aurafuron A

The first total synthesis of (-)-aurafuron A is presented. It features a Suzuki cross-coupling reaction and a high yielding anionic aldol addition as central carbon skeleton building reactions. The synthesis confirms the proposed structure including its configuration and allows for detailed SAR studies.     

A ridge walk between reaction modes: an unprecedented Pd-catalyzed domino sequence of diynyl-substituted bromoarenes

Diynyl-substituted bromoarenes underwent a novel Pd-catalyzed domino reaction to provide benzofurans, pyridinofurans, isochromenes, and indole derivatives. Slight changes of the substrate push the reaction in another direction resulting in benzene annulation.     

Multivariate statistics for the differentiation of erythropoietin preparations based on intact glycoforms determined by CE-MS

Owing to the increasing number of erythropoietin biosimilars being approved, the comparison of different erythropoietin preparations in the pharmaceutical area is gaining in importance. Erythropoietin has a distinct natural heterogeneity arising from its glycosylation, which shows strong composition variations. This heterogeneity increases the complexity of the analysis of erythropoietin considerably, but may also be used to distinguish different preparations. Here, a method is presented for the differentiation of various erythropoietin preparations by capillary electrophoresis–mass spectrometry and the subsequent application of multivariate statistics. Relative peak areas of selected intact erythropoietin isoforms were used as variables in principal component analysis and hierarchical agglomerative clustering. Both of these strategies were suited for the clear differentiation of all erythropoietin preparations, including marketed products and preproduction preparations, which differ in the manufacturer, the production cell line, and the batch number. By this means, even closely related preparations were distinguished on the basis of the combined information on the antennarity, the sialoform, and the acetylation of the observed isoforms.     

The facile reduction of carbon dioxide to carbon monoxide with an amido-digermyne

Taking the fizz out: A digermyne compound with a Ge?Ge single bond has been shown to quantitatively reduce CO(2) to CO at temperatures as low as -40?°C. The mechanism of this unprecedented reaction has been probed by spectroscopic and computational techniques and involves a metastable intermediate (see picture; Ar*=C(6) H(2) {C(H)Ph(2) }(2) Me-2,6,4).     

Enantioselective Titanium(III)-Catalyzed Reductive Cyclization of Ketonitriles

Reduction, please! The title reaction affords α-hydroxyketones, a common structural motif in biologically active natural products, in good yields and high enantioselectivities at room temperature. The commercially available ansa-titanocene 1 was found to be an efficient catalyst for this process, which presumably proceeds by addition of a ketyl radical to a nitrile.