Light-Activated Assembly of DNA Origami into Dissipative Fibrils

Hierarchical DNA nanostructures offer programmable functions at scale, but making these structures dynamic, while keeping individual components intact, is challenging. Here we show that the DNA A-motif—protonated, self-complementary poly(adenine) sequences—can propagate DNA origami into one-dimensional, micron-length fibrils. When coupled to a small molecule pH regulator, visible light can activate the hierarchical assembly of our DNA origami into dissipative fibrils. This system is recyclable and does not require DNA modification. By employing a modular and waste-free strategy to assemble and disassemble hierarchical structures built from DNA origami, we offer a facile and accessible route to developing well-defined, dynamic, and large DNA assemblies with temporal control. As a general tool, we envision that coupling the A-motif to cycles of dissipative protonation will allow the transient construction of diverse DNA nanostructures, finding broad applications in dynamic and non-equilibrium nanotechnology.     

Stereochemical resolution of enantiomeric 2-aryl propionic acid non-steroidal anti-inflammatory drugs on a human serum albumin based high-performance liquid chromatographic chiral stationary phase

Summary The native enantioselectivity in binding of human serum albumin (HSA) towards 2-aryl propionic acid non-steroidal anti-inflammatory drugs (2-APA-NSAIDs, the profens) was found to be preserved when the protein was immobilized within a commercially available diol high-performance liquid chromatographic column. High capacity factors were obtained, reflecting the previously observed extensive binding of the 2-APA-NSAIDs to free HSA. The capacity factors were modified by the addition of octanoic acid to the mobile phase. Chiral resolution of the enantiomers of all nine 2-APA-NSAIDs studied was achieved. Preliminary studies show that in addition to being a useful chiral analytical tool for this therapeutically important series of compounds, the HSA chiral stationary phase may provide useful information on the affinity and binding mechanism of small molecules to HSA.     

Manganese(I)-Catalyzed Regioselective C−H Allenylation: Direct Access to 2-Allenylindoles

A Mn^I-catalyzed regioselective C−H allenylation is reported that allows a broad range of 2-allenylindoles to be synthesized regioselectively on a gram scale under simple conditions. Notably, a highly efficient chirality transfer was observed (up to 93 % ee) in this transformation. This procedure was further found to allow, for the first time, the direct preparation of ketones by Mn^I-catalyzed C−H activation. Mechanistic investigations revealed that the precoordination of the oxygen atom to the manganese center as well as the congested tertiary carbon atom in the propargylic carbonates play a crucial role.     

Et2Zn-mediated stoichiometric C(sp)-H silylation of 1-alkynes and chlorosilanes

A first example of an Et₂Zn mediated silylation of 1-aklynes is reported. A series of functional groups are tolerated in this reaction. Mechanistic studies support Zn alkynilides as intermediates in the reaction. This reaction protocol provides a practical method for the preparation of alkynylsilanes and expands the application of organometallic zinc in organic synthesis.     

Lipophilic Diamides as Ionophores for Alkali and Alkaline Earth Metal Cations

A series of lipophilic N, N, N′,N′-tetrasubstituted diamides were prepared and their selectivity in solvent polymeric membranes was studied, cis-N, N, N′, N′-Tetraisobutylcyclohexane-1,2-dicarboxamide induces a selectivity in membranes for Li⁺over alkaline earth metal cations and other alkali metal cations by a factor of about 1000 and 100 respectively. The ionophore N, N′-diheptyl-N,N′-dimethylethylmalonamide is an attractive candidate for the use in microelectrodes for the determination of intracellular Mg²⁺-activities.     

Effect of laser illumination oxidation-reduction cycles upon surface-enhanced Raman scaterring from silver electrodes

The intensity of surface-enhanced Raman scattering (SERS) from thiocyanate and chloride adsorbed on silver electrodes is shown to depend critically on whether the electrode is illuminated during the oxidation-reduction cycle used to pretreat the electrode. The value and magnitude of the photoeffect is dependent upon the type of surface vibrational mode, the adsorbate and the wavelength of the radiation during the ORC. The effects are attributed to the production of SERS active clusters of Ag atoms by photoreduction of the Ag(I) phase films during the ORC.     

Homogenization of periodic micro-structures with FFT-based higher order schemes

A matrix-free homogenization method making use of the fast Fourier transform (FFT) to work on structured grids was introduced by Moulinec and Suquet in 1994. Due to its simplicity and computational advantages, this so-called Basic Scheme has provided the basis for many works in the past two decades. An extension presented by Tran, Monchiet and Bonnet allows for the quasi-static equations of linear elasticity to include effects from higher-order derivatives by expanding the strain and the displacement as asymptotic series. To compute the solution hierarchically, we derive generalized Lippmann Schwinger-type equations. Furthermore, we show how existing algorithms have to be adapted for these problems. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)