Tyrosinases are essential enzymes that occur in all organisms and belong to the class of type3 copper proteins. The first crystal structure of a tyrosinase (from Streptomyces castaneoglobisporus) has been achieved and offers important insights into the mechanism of phenol hydroxylation (see scheme; Cu blue, O red, substrate orange; trans-axial position on CuA: gray dot), the process of activation, and the incorporation of copper.

Small can do too: Recent research on transcriptional factors has uncovered small-molecule ligands that are able to modulate gene transcription by interacting with multiprotein complexes. Some of these compounds bind to different sites on the target proteins and therefore exert different functions. The picture shows the association of the HDM2 protein (bronze) with the tumor suppressor p53 (green), and two small molecules that influence p53 function positively.

Dye another day: Modern donor and acceptor materials for fluorescence resonance energy transfer (FRET) analyses (see picture) comprise photochromic dyes, semiconductor nanocrystals, nanoparticles, fluorescent amino acids, polymers, and genetically encoded protein, in additional to “traditional” organic dyes. The scope and boundaries of such systems, as well as avaible methods for bioconjugation are discussed, with an emphasis on the combination of different materials.

Promoting the atomic dialogue! At neutral pH and ambient temperature, a cyclodextrin-derived ketone causes hydrogen peroxide and benzyl alcohols to meet in its active site and react up to 60 000 times faster than they do outside the cyclodextrin.

A clue to the origin of chirality? A solution of proline with high enantiomeric excess (85–99 % ee) was obtained from solid proline of only 10 % ee through novel dissolution and crystallization processes (see scheme). This observation may be an explanation for the origin of chirality on Earth.

A scattering of silver: Polyhedral silver nanocrystals display complex and distinct scattering signatures dictated by their shape and size (see picture). The ability to engineer specific plasmon modes should have profound consequences for surface-enhanced Raman spectroscopy, subwavelength optics, and plasmonic transport.

Light twisting and untwisting: UV light was found to drive reversible helical-nanofiber formation based on the photodimerization and photodissociation of the thymine residue in the 1,ω-thymidylic acid appended bolaamphiphile. ¹H NMR spectroscopy revealed that UV irradiation of the self-assembled nanofibers induces a helical structure through the formation of a cis–syn isomer of the thymine moiety.

A bit on the side: A side-chain polyrotaxane that consists of simple components is successfully constructed and controlled by using photoisomerization of an azobenzene moiety at the terminal of the side chain.

Arrested precipitation of In₂S₃ affords ultrathin hexagonal nanoplates with 0.76-nm thickness and controllable sizes of 22–63 nm. The pictures show (from left to right) TEM images of 63-nm nanoplates aligned parallel to a support, a side view of nanoplates, and 45-nm nanoplates self-assembled into microwires.

Escape route: The laser-initiated release of fluorescently labeled polymers from polyelectrolyte-multilayer microcapsules is demonstrated inside living cancer cells. A polymer is incorporated in capsules with metal nanoparticles in their walls, which serve as light-absorbing centers. The capsules are internalized by cells and near-infrared light ruptures the walls of the capsules, thus releasing the content into the cells.

Surprisingly stable anti-periplanar conformers of CFTA amides form the basis of a new and very reliable method for determining the absolute configuration of chiral primary amines by ¹H NMR spectroscopy (see picture). CFTA=α-cyano-α-fluoro-p-tolylacetic acid.

Playing the field: Application of an electric field to the thermodynamic equilibria of constitutionally dynamic sets of imines and amines that contain an imine with liquid-crystalline properties and a negative dielectric anisotropy leads to the amplification of the constituent that couples most strongly to the electric field, namely the liquid crystal (LC, see example). The field can thus induce a liquid to nematic phase transition.

Swapping partners: The presence of N-oxide functions in double-helical dimers formed from oligo(pyridinecarboxamide)s promotes heterodimerization (see picture). This process mimicks the essence of base pairing and information storage in DNA through heterologous A/T and G/C Watson–Crick base pairing.

Neutral organic guest molecules are confined within the cavities of a porous coordination polymer. The key interaction is that of electron-deficient π planes of the polymer surface with electronegative atoms of the guest molecules (see picture). Evidence from thermogravimetric analysis suggests that guests with two electronegative atoms form more-stable complexes with the polymer than those with one electronegative atom.

Casting clusters from the mold: Tris(ethylzinc) phosphazenates exhibit a bowl-shaped coordination surface of three Lewis acidic EtZn moieties and three Lewis basic N sites. This surface provides a perfect mold for planar {(ZnO)₃} rings and hexagonal {(ZnO)₆} prisms. The zinc oxide clusters were generated in situ by reaction of phosphazene hydrates with diethylzinc.

Two for the price of one: The total synthesis of (+)-cylindricine C has been achieved in six steps using a catalytic asymmetric Michael reaction and tandem cyclization. A newly designed two-center organocatalyst gives good selectivity in this Michael reaction. TaDiAS=tartrate-derived diammonium salt.

Hooking up: Self-assembly of a porphyrin amidine and fulleropyrrolidine carboxylic acid based on a two-point amidinium–carboxylate motif leads to supramolecular dyads of high stability (K_a≈10⁷ M⁻¹ in toluene/acetonitrile (9:1)). The synergy of the hydrogen bonds and electrostatic interactions has been shown to be particularly beneficial in terms of electronic coupling between both electroactive components of the dyads.

Successful matchmaking: The combination of a chiral nitrene precursor with a chiral rhodium(II) catalyst is the key factor that allows efficient intermolecular regioselective CH amination. Good-to-excellent yields and excellent diastereoselectivities can be obtained with a stoichiometric amount of the CH bond containing substrate. nttl=N-1,8-naphthoyl-tert-leucine.

In a (nut)shell: Covalently wrapped in a protecting and solubilizing dendrimeric shell (see picture), an initially hydrophobic two-photon fluorophore becomes a biocompatible contrast agent with strong emission for imaging in vivo by multiphoton microscopy.

Wine into vinegar: It is possible to selectively oxidize ethanol into acetic acid in aqueous solution with air as the oxidant and a heterogeneous gold catalyst (see TEM image of supported gold particles) at temperatures of about 423 K and O₂ pressures of 0.6 MPa. This reaction proceeds readily in aqueous acidic media with yields of up to 90 % and CO₂ as the only major by-product.

Gold is not so inert after all! X-ray absorption spectroscopy was used to probe the activation of O₂ and its reaction with CO over an Au/Al₂O₃ catalyst. The catalytic activity of small gold particles in the oxidation of CO arises from their ability to transfer charge to oxygen (see picture).

Tin inside In: Hollow and tin-filled nanotubes of single-crystalline In(OH)₃ are grown in a one-step solution–liquid–solid–solid (SLSS) process, and the structural properties of nanotubes synthesized under different growth conditions characterized and studied. The nanofluidic properties of the interior Sn (see picture) are demonstrated by its response to a rising environmental temperature brought about by electron-beam irradiation.

Highly attractive: Features typical of a single-molecule magnet (that is, a high anisotropy barrier of 25 K, very slow zero-field relaxation, and a large coercive field of 15 kOe) are exhibited by a Dy^IIICu^II nonanuclear complex, which was synthesized by using a Schiff base ligand. The picture shows the {DyCuO} core of the cluster (dark green Dy, light green Cu, red O) and low-temperature magnetization curves.

A Möbius arrangement of the bonds directly attached to a metallamacrocycle was observed for the Au^I complex [Au₃(CNC)(μ-Ph₂PCH₂PPh₂)₂]⁺, which was self-assembled by treating the lithium salt of pyridyl-2,6-diphenyl²⁻ (CNC) with [Au₂Cl₂(μ-Ph₂PCH₂PPh₂)]. The trinuclear Au^I complex has intramolecular Au⋅⋅⋅Au and CH⋅⋅⋅π interactions, exhibits a remarkable stability in solution, and is cytotoxic toward cancer cell lines.

A novel spin-polarization mechanism involving the intramolecular ion pair *A^.−-D^.+-R, which competes with a spin–orbit intersystem crossing, is proposed for the formation of the uniquely spin-polarized quartet photoexcited state observed for 1, which consists of a bodipy acceptor (A), a phenylanthracene donor (D), and a stable verdazyl radical (R).

Tamed OATS: A scheme that integrates homogeneous biocatalysis in organic–aqueous mixtures with CO₂-induced separation has been developed. This method allows for simultaneous product recovery and recycling of the homogeneous biocatalyst for reuse.

Re-discovery: The only rhenium(VII)–chlorine compound known previously was ReO₃Cl, and chloride oxides of composition AO₂Cl₃ (A=nonmetal or metal) were completely unknown. The synthesis of ReO₂Cl₃ has now been achieved. The compound exists as a chlorine-bridged dimer (see Figure; Re red, O blue, Cl green) in the solid state, and as a monomer in solution.

A good beginning is half the battle. Combined experimental and theoretical studies concerning the dehydrogenation of hydrocarbons by [V₃O₇]⁺ underline the decisive role of the initial CH activation step. Propane is found to be unreactive, whereas 1-butene rapidly reacts with [V₃O₇]⁺ (see picture).

Hand in hand: In a combination of experimental (mass spectrometry) and theoretical (density functional theory) studies [V₄O₁₀]⁺ is described as the first polynuclear transition-metal oxide capable of activating methane at room temperature (see picture). The [V₄O₁₀]⁺ cation can be considered a prototype of oxide clusters of early 3d transition metals.

Round up: A fully conjugated cyclododeca-2,7-carbazole is prepared around a porphyrin template and the corresponding empty macrocycle then released. Single molecules could be visualized by STM (see image) and their arrangement by atomic force microscopy. The macrocycles self-assemble into a hexagonal array of columns. Efficient energy transfer occurs from the peripheral carbazole π system to the central porphyrin core.