RNA Cleavage Catalyzed by Amphoteric Bis(acyl)guanidinium Derivatives

Described herein are two series (twelve compounds each) of very closely related guanidinium‐based receptors and their ability to catalyze hydrolytic cleavage of a unique RNA substrate – oligo‐dT flanked t rans‐ A ctivation R esponsive region of the HIV‐1 mRNA, TAR RNA. The significant difference in activities of otherwise very similar compounds is discussed, and direct and indirect evidences supporting our interpretation are presented. The results indicate that improvements in catalytic efficiency could be achieved with little modification of the structure of a relatively weak catalyst, and that a crucial feature could be a finely calibrated interplay between anion‐binding and proton‐donating abilities.     

Adaptive Modelling,Simulation and Optimization of Gas and Water Supply Networks

We consider the simulation and optimisation of transport processes through gas and water supply networks. Using a consistent modeling of the network, adjoint equations for the whole system including initial, coupling and boundary conditions can be derived. These are suitable to compute gradients for optimization tasks but can also be used to estimate the accuracy of models and the discretization with respect to a given cost functional. We show the applicability of an adaptive algorithm that automatically steers the discretization and models while maintaining a given accuracy in an optimisation framework. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Chemical mimicry: hierarchical 1D TiO2@ZrO2 core-shell structures reminiscent of sponge spicules by the synergistic effect of silicatein-α and silintaphin-1

In nature, mineralization of hard tissues occurs due to the synergistic effect of components present in the organic matrix of these tissues, with templating and catalytic effects. In Suberites domuncula, a well-studied example of the class of demosponges, silica formation is mediated and templated by an axial proteinaceous filament with silicatein-α, one of the main components. But so far, the effect of other organic constituents from the proteinaceous filament on the catalytic effect of silicatein-α has not been studied in detail. Here we describe the synthesis of core-shell TiO(2)@SiO(2) and TiO(2)@ZrO(2) nanofibers via grafting of silicatein-α onto a TiO(2) nanowire backbone followed by a coassembly of silintaphin-1 through its specifically interacting domains. We show for the first time a linker-free, one-step funtionalization of metal oxides with silicatein-α using glutamate tag. In the presence of silintaphin-1 silicatein-α facilitates the formation of a dense layer of SiO(2) or ZrO(2) on the TiO(2)@protein backbone template. The immobilization of silicatein-α onto TiO(2) probes was characterized by atomic force microscopy (AFM), optical light microscopy, and high-resolution transmission electron microscopy (HRTEM). The coassembly of silicatein-α and silintaphin-1 may contribute to biomimetic approaches that pursue a controlled formation of patterned biosilica-based biomaterials.     

Solution synthesis of nanoparticular binary transition metal antimonides

The preparation of nanoengineered materials with controlled nanostructures, for example, with an anisotropic phase segregated structure or a regular periodicity rather than with a broad range of interparticle distances, has remained a synthetic challenge for intermetallics. Artificially structured materials, including multilayers, amorphous alloys, quasicrystals, metastable crystalline alloys, or granular metals, are mostly prepared using physical gas phase procedures. We report a novel, powerful solution-mediated approach for the formation of nanoparticular binary antimonides based on presynthesized antimony nanoparticles. The transition metal antimonides M-Sb (M = Co, Ni, Cu(2), Zn) were obtained with sizes ranging from 20 and 60 nm. Through careful control of the reaction conditions, single-phase nanoparticular antimonides were synthesized. The nanophases were investigated by powder X-ray diffraction and (high resolution) electron microscopy. The approach is based on activated metal nanoparticles as precursors for the synthesis of the intermetallic compounds. X-ray powder diffraction studies of reaction intermediates allowed monitoring of the reaction kinetics. The small particle size of the reactants ensures short diffusion paths, low activation barriers, and low reaction temperatures, thereby eliminating solid-solid diffusion as the rate-limiting step in conventional bulk-scale solid-state synthesis.     

Wet chemical synthesis and a combined X-ray and Mössbauer study of the formation of FeSb2 nanoparticles

Understanding how solids form is a challenging task, and few strategies allow for elucidation of reaction pathways that are useful for designing the synthesis of solids. Here, we report a powerful solution-mediated approach for formation of nanocrystals of the thermoelectrically promising FeSb(2) that uses activated metal nanoparticles as precursors. The small particle size of the reactants ensures minimum diffusion paths, low activation barriers, and low reaction temperatures, thereby eliminating solid-solid diffusion as the rate-limiting step in conventional bulk-scale solid-state synthesis. A time- and temperature-dependent study of formation of nanoparticular FeSb(2) by X-ray powder diffraction and iron-57 M?ssbauer spectroscopy showed the incipient formation of the binary phase in the temperature range of 200-250 °C.     

Controlling phase formation in solids: rational synthesis of phase separated Co@Fe2O3 heteroparticles and CoFe2O4 nanoparticles

A wet chemical approach from organometallic reactants allowed the targeted synthesis of Co@Fe(2)O(3) heterodimer and CoFe(2)O(4) ferrite nanoparticles. They display magnetic properties that are useful for magnetic MRI detection.     

Quantification of surface functional groups on polymer microspheres by supramolecular host-guest interactions

We introduce a method to determine the number of accessible functional groups on a polymer microsphere surface based on the interaction between the macrocyclic host cucurbit[7]uril (CB7) and a guest reacted to the microsphere surface. After centrifugation, CB7 in the supernatant is quantified by addition of a fluorescent dye. The difference between added and detected CB7 affords the number of accessible surface functional groups.     

The interface between Au(100) and 1-butyl-3-methyl-imidazolium-hexafluorophosphate

The electrochemical interface of Au(100) and 1-butyl-3-methyl-imidazolium hexafluorophosphate has been characterized by cyclic voltammetry, electrochemical impedance spectroscopy and in situ STM, especially in two distinct potential ranges. In the vicinity of the potential of zero total charge--the value of which has been determined by immersion experiments--charging of the double layer is rather slow, it appears as if the ions comprising the ionic liquid would slowly exchange each other at the surface. In the other, very negative region the ordering of the cations has been observed by STM.