Transient DNA-Based Nanostructures Controlled by Redox Inputs

Synthetic DNA has emerged as a powerful self-assembled material for the engineering of nanoscale supramolecular devices and materials. Recently dissipative self-assembly of DNA-based supramolecular structures has emerged as a novel approach providing access to a new class of kinetically controlled DNA materials with unprecedented life-like properties. So far, dissipative control has been achieved using DNA-recognizing enzymes as energy dissipating units. Although highly efficient, enzymes pose limits in terms of long-term stability and inhibition of enzyme activity by waste products. Herein, we provide the first example of kinetically controlled DNA nanostructures in which energy dissipation is achieved through a non-enzymatic chemical reaction. More specifically, inspired by redox signalling, we employ redox cycles of disulfide-bond formation/breakage to kinetically control the assembly and disassembly of tubular DNA nanostructures in a highly controllable and reversible fashion.     

Protein-Controlled Actuation of Dynamic Nucleic Acid Networks by Using Synthetic DNA Translators**

Integrating dynamic DNA nanotechnology with protein-controlled actuation will expand our ability to process molecular information. We have developed a strategy to actuate strand displacement reactions using DNA-binding proteins by engineering synthetic DNA translators that convert specific protein-binding events into trigger inputs through a programmed conformational change. We have constructed synthetic DNA networks responsive to two different DNA-binding proteins, TATA-binding protein and Myc-Max, and demonstrated multi-input activation of strand displacement reactions. We achieved protein-controlled regulation of a synthetic RNA and of an enzyme through artificial DNA-based communication, showing the potential of our molecular system in performing further programmable tasks.     

Copper-catalyzed N-arylation of imidazoles and benzimidazoles

4,7-Dimethoxy-1,10-phenanthroline (L1c) was found to be an efficient ligand for the copper-catalyzed N-arylation of imidazoles and benzimidazoles with both aryl iodides and bromides under mild conditions. Further optimization of the system has revealed that the addition of poly(ethylene glycol) accelerates this reaction. A variety of hindered and functionalized imidazoles, benzimidazoles, and aryl halides were transformed in good to excellent yields. Heteroaryl halides were also coupled in moderate to good yields. We also present the results obtained from a series of coupling reactions, which directly compare the use of L1c with other recently reported ligands.     

Butane and propane oxidation by engineered cytochrome P450cam

The haem monooxygenase cytochrome P450cam has been engineered to oxidise the gaseous alkanes butane and propane to butan-2-ol and propan-2-ol, respectively, by the use of bulky amino acid substitutions to reduce the volume of the substrate pocket and thus improve the enzyme-substrate fit: the F87W/Y96F/T101L/V247L mutant oxidizes butane with a turnover rate of 750 min-1 and 95% yield based on NADH consumed while the wild-type enzyme has an activity of 0.4 min-1 with 4% yield.     

Facile mechanosynthesis of amorphous zeolitic imidazolate frameworks

A fast and efficient mechanosynthesis (ball-milling) method of preparing amorphous zeolitic imidazolate frameworks (ZIFs) from different starting materials is discussed. Using X-ray total scattering, N(2) sorption analysis, and gas pycnometry, these frameworks are indistinguishable from one another and from temperature-amorphized ZIFs. Gas sorption analysis also confirms that they are nonporous once formed, in contrast to activated ZIF-4, which displays interesting gate-opening behavior. Nanoparticles of a prototypical nanoporous substituted ZIF, ZIF-8, were also prepared and shown to undergo amorphization.     

Reliability of fibres in solid-phase microextraction for routine analysis of the headspace of aromatic and medicinal plants

This article evaluates the HS-SPME recovery repeatability, intermediate precision and their performance over time when applied to HS-SPME sampling for quality control of medicinal and aromatic plants. Experiments were carried out on two sets of fibres coated with two different coatings and belonging to different lots (i.e 100 microm polydimethylsyloxane (PDMS) and Carboxen/divinylbenzene/PDMS 50/30 microm, l: 1 cm (CAR/DVB/PDMS)) and on chamomile (Matricaria chamomilla L.), sage (Salvia lavandulifolia Vahl.) and a standard solution containing 3-hexanol, isoamyl acetate, 1,8-cineole and menthol in diisobutyl phthalate. The performance of each set of fibres was evaluated by determining a group of complementary statistical parameters including: (i) repeatability of the absolute areas of each marker from each matrix with each fibre; (ii) intra-fibre repeatability of the total absolute areas of the markers of each matrix obtained with each fibre of each set; (iii) inter-fibre intermediate precision of the total absolute areas of the markers of each matrix obtained with all fibres of each set; and (iv) analysis of variance by one-way ANOVA with Fisher and Tukey tests. The influence of the number of analyses on fibre effectiveness (fibre life-time) was studied by linear regression analysis (LRA). The results proved that HS-SPME can successfully be used for routine control analysis of aromatic ad medicinal plants since both types of fibres showed good repeatability and intermediate precision of analytes recovery and consistency over time. Unlike data previously reported by other authors, CAR/DVB/PDMS coated fibres gave better results than those coated with PDMS. The fibre-life seemed mainly to be influenced by the number and conditions of samplings and nature of the matrix investigated.     

Printable superhydrophilic-superhydrophobic micropatterns based on supported lipid layers

A new and simple method for creating superhydrophilic micropatterns on a superhydrophobic surface is demonstrated. The method is based on printing an "ink", an ethanol solution of a phospholipid, onto a porous superhydrophobic surface and, thus, is compatible with a variety of commonly available printing techniques.     

Tacitation and implicitation: the construction of semiotic tools for representing mathematics teaching

Representations are an account of reality. Their construction involves several choices: what to represent, how to represent, from which point of view. Here, we introduce tools to represent mathematics teaching through the study of sign exchanges. We first emphasize how signs are tightly related to different shares of knowledge of sign users. In the regular case, sign exchanges are considered to rest on a kind of shared obviousness. The knowledge imbalance between actors of the didactical situation renders this shared obviousness minimal, and therefore requires distinguishing different kinds of sign exchange processes. From the notion of semiosis, we define the processes of tacitation and implicitation. We present a field study from these theoretical concepts and discuss some implications for future research.     

Synthesis of Aluminum N,N-Dialkylcarbamates by Insertion of CO2 into Al−N Bonds

Despite decades of research on various carbamates and their important applications, only one aluminum N,N-dialkylcarbamate (ADC) with an aluminum:carbamate ratio of 1 : 3 has been structurally described and comprehensively studied so far, namely tris(diisopropyl)carbamate. The reasons for this situation include problems with the used synthetic routes. The process of CO₂ insertion into Al−N bonds of tris(dialkylamido)alanes resolved these difficulties. Using this advantageous synthetic route, the dimethyl and diethyl, as well as the pyrrolidino, piperidino, and N-methylpiperazino derivatives were now successfully prepared. These ADCs were investigated by solid-state NMR spectroscopy, where line-shape analyses of the ²⁷Al NMR spectra allowed conclusions with respect to the determination of the quadrupole coupling parameters. Furthermore, data of an intermediate during the CO₂ insertion into tris(diisopropylamido)alane were obtained by in-situ IR spectroscopy, which were complemented by NMR measurements of samples periodically taken during the reaction. Partial hydrolysis of tris(pyrrolidino)carbamate revealed a complex Al₃(μ₃-O) cluster structure, which was elucidated by single crystal X-ray diffraction.