Angewandte Chemie International Edition

Biomolecular nanopatterns can be quickly fabricated over a large area with a resolution down to 10 nm by magnetic electric lithography, as reported by Z. Gu, S. Huang, and Y. Chen in their Communication on page 952 ff. Magnetic nanoparticles coated with multiple distinct biomolecules are deposited by a magnetic field and immobilized onto nanoelectrodes by an electric field to generate arbitrary heterogeneous biomolecular nanopatterns, which can then be printed onto polymer films for diverse biomedical applications.

A deserted island illustrates the weakly coordinating nature of a sterically shielded cation, as described by S. A. Miller and co-workers in their Communication on page 956 ff. Such sterically encumbered cations offer a strategy complementary to that of weakly coordinating anions for diminishing cation–anion interactions. The steric differences are reflected in the absorption maxima of the complexes, which in turn can be detected by the naked eye (green vs. purple).

Toss the olefin into the porphyrin: The development of chiral cobalt(II)–porphyrin catalysts by straightforward coupling processes has made possible the additions of diazocarbonyl compounds to a broad spectrum of olefins to access functionalized cylopropanes. The cyclopropanation reactions demonstrate high product yields, exceptional diastereoselectivity, and excellent enantiocontrol.

Inhibition or degradation? MicroRNAs have been considered primarily as inhibitors of translation, even though degradation of mRNAs also plays a role in their repressive potential. Two research groups have now quantified the extent to which each mechanism contributes to gene regulation by combining mass spectrometry with transcriptome profiling. The surprising conclusion is that translational inhibition plays only a minor role!

A spotlight on light signaling: Molecular beacons are specifically designed DNA hairpin structures (see picture) used as fluorescent probes for numerous bioanalytical applications, including gene detection, the monitoring of messenger RNA (mRNA), and biosensing. Recent studies have led to versatile strategies for the targeted optimization of molecular beacons. ssDNA=single-stranded DNA.

Future of nanomedicine: Multiple functions can be integrated into nanoparticle systems for drug delivery. The schematic representation of a third-generation nanovector illustrates this: On the outside are recognition units to interact with target cells and biological barriers, while inside are drug-loaded nanoparticles, which leave the vector at the correct moment and release their load.

Binding motifs of aminopyrazole derivatives with different peptides in the gas phase are investigated by using mass- and isomer-selective IR/UV spectroscopy. The efficiency of blocking a β-sheet model is determined by analyzing the number and strength of hydrogen bonds (see picture). The investigations yield information on intrinsic molecular properties of beginning aggregation behavior, as might also occur in misfolding diseases.

G“Ru”vy reactivity: The new ruthenium(II) complex having cooperative PNP enamido ligand A reversibly activates two equivalents H₂ under reversible hydrogenation of amido (B) and amino (C) complexes. B exhibits the highest reported activities in the dehydrocoupling of ammonia–borane.

Surprisingly straightforward: A metal-free, highly enantioselective Brønsted acid catalyzed condensation/addition reaction has been developed for the construction of 2,3-dihydroquinazolinones starting from 2-aminobenzamide and aldehydes (see scheme). This efficient approach provides 2,3-dihydroquinazolinones with a strong preference for the S enantiomers, which have higher biological activities than the R enantiomers.

Two novel synthetic strategies were developed for the natural products geovanine, marcanine A, and kalasinamide. The nine-step synthesis of geovanine marks its first total synthesis. The three compounds are known for their antimalarial and antitumor activity, and tests confirmed the high cytotoxity of marcanine A.

After 50 years of persistence the 12-membered cyclic skeleton of bottromycin A₂ (3) has been confirmed by NMR experiments (HMBC), and the configurations of two tLeu residues have been estimated by conformation analysis and NMR experiments. Furthermore, the key step in the synthesis of 3 involves the mercury-mediated formation of the amidine of thioamide 1 and amine 2.

The phenol countdown: Novel imidazole-based phosphine ligands are synthesized on scales up to 100 g by a convenient lithiation–phosphorylation method. The phosphines are stable towards air and moisture and are successfully applied as ligands in the palladium-catalyzed selective hydroxylation of aryl halides (see scheme, dba=dibenzylideneacetone).

Neatly folded: A decameric β-peptide shows enzyme-like catalytic properties. The foldamer, which bears a terminal heptanoyl unit and displays a thermostable helical structure with an array of ammonium-group side chains, accelerates a retroaldol reaction (see scheme) by more than three orders of magnitude through an imine mechanism.

Four from one: Nanoscale ribbons, tubes, vesicles, and platelets can be formed from the self-assembly of a single covalent unit, which is based on an amphiphilic perylene diimide functionalized with a terpyridine ligand (see picture). The assembly diversity arises from the encoding of multiple inputs through hydrophobic interactions and metal coordination.

Low-pressure catalyst: A novel dizinc complex (1) having a macrocyclic ancillary ligand shows remarkable activity for the copolymerization of carbon dioxide and cyclohexene oxide, at only one atmosphere of CO₂. TON=turnover number; TOF=turnover frequency.

An acyl triphosphirene ligand transfers an O atom to Nb to liberate the putative triphosphacyclobutadiene intermediate [RCP₃{W(CO)₅}₂], which engages in [2+4]-cycloaddition reactions with an organic diene and a phosphaalkyne (see scheme; P orange, O red, W violet, C white). The latter reaction yields the Dewar isomer of a tetraphosphabenzene, which can be converted to a tetraphosphabenzvalene containing a Z-diphosphene.

The right sort: A post-synthesis, liquid-phase separation method sorts nanoparticles by centrifugation in a medium with a density gradient. The particles are sorted according to particle size, clustering degree, and core density ρ (see picture; d=sedimentation distance). Solid–solid interactions between colloidal particles and stable phases are thus avoided. This versatile method allows for determination of the colloid size distribution in a suspension.

I see the light: When an electroactive inverse polymer-gel opal is electrochemically oxidized and reduced, the lattice swells and shrinks, respectively. Concomitantly the wavelength of brightly diffracted light can be altered all the way from the ultraviolet through the visible to the near infrared (see picture).

Dendritic cell-wall mimics: Choline-binding proteins from Streptococcus pneumoniae recognize distinctive multivalent choline architectures on the bacterial cell wall. Choline-functionalized dendrimers are potent inhibitors of these essential enzymes, with a 10³–10⁴-fold higher affinity than free choline, resulting in inhibition of autolysis and cell separation in bacterial cultures at low micromolar concentrations (see picture).

Paint by number? Magnetic nanoparticles (MNPs) coated with distinct biomolecules (see picture) can be assembled onto nanoelectrodes on a template under the control of magnetic and electric fields. The MNP–biomolecule conjugates can then be transferred from the template to a biocompatible polymer substrate. Arbitrary nanopatterns can be fabricated by the magnetic electric lithography process over a large area with a resolution down to 10 nm.

Big is beautiful: Activation of fluorenyl-based zirconocenes with methylaluminoxane (MAO) effects a red shift in the visible λ_max proportional to the size of the metallocene (see potential energy surfaces in picture). Polymerization activities correlate directly with color (λ_max), suggesting that bulky zirconocenium catalysts are weakly coordinating cations which, like weakly coordinating anions, diminish cation–anion interactions.

A preorganized zipper: The entropic penalty for duplex formation is significantly smaller for the backbone-simplified nucleic acid analogue GNA (glycol nucleic acid) than for DNA. This finding is consistent with a conformational preorganization of the single strands in combination with especially favorable stacking interactions in the corresponding GNA duplex (see picture).

First class delivery: Core–shell structured nanoassemblies could be constructed from a hydrophilic–hydrophilic block copolymer with one block containing β-cyclodextrin in the presence of hydrophobic guest compounds (see picture). The polymer can host various guest molecules, while the difference in sensitivity can be utilized to regulate release rate. By selecting appropriate guests, polyion complex (PIC) micelles could also be assembled.

Quick release: The spatial and temporal delivery of active molecules (dyes or drugs) can be precisely controlled by the photocatalytic activity of TiO₂ nanotubes (see picture). The cleavage of the link between the active molecule and the nanotubes, which are filled with magnetic Fe₃O₄ nanoparticles, occurs by photoinduced chain scission under UV light; the load can be released before photodegradation by action of photogenerated radicals can occur.

It isn't easy BN aromatic! 1,2-Dihydro-1,2-azaborine, a hybrid organic/inorganic benzene, is a stable aromatic molecule with features that are distinct from its isoelectronic “organic” (benzene) and “inorganic” (borazine) counterparts. Experimental structural, spectroscopic, and chemical data are fully supported by high-level calculations.

Gelling together: A three-dimensional, biocompatible hydrogel (see picture) was generated by combining two cationic polymers, chitosan and poly(ethylenimine). The hydrogels were stable under cell-culture conditions and facilitated cell proliferation, yet prevented dedifferentiation of primary human skeletal cells into fibroblasts. A variety of materials such as DNA, proteins, and peptides can be stably incorporated into the gel network.

Make a stand: The formation of stable and ordered free-standing particle bridges and hollow capsule structures with controllable sizes and geometries is demonstrated by combining the directed assembly of submicrometer particles, transfer printing, and supramolecular layer-by-layer assembly.