Deconstructing Oligomer Distributions: Discrete Species and Artificial Distributions

The separation of an oligo(methyl acrylate) distribution, obtained from reversible addition–fragmentation chain transfer (RAFT) polymerization, in a discrete (dispersity=1) oligomeric library (degree of polymerization between 1 and 22) is presented. The properties of this library in terms of diffusivity, glass transition temperature, and viscosity are determined, filling a significant knowledge gap associated with these materials. The obtained oligomer library is used to construct artificial oligomer distributions on demand. These artificial oligomer distributions are used to highlight the potential to tailor physical properties of a material, while concomitantly demonstrating the limitations associated with size‐exclusion chromatography analysis of molecular weight and dispersity in particular.     

The Fundamental Group of a Noncommutative Space

Algebras and Representation Theory - We introduce and analyse a general notion of fundamental group for noncommutative spaces, described by differential graded algebras. For this we consider...     

Hedycaryol – Central Intermediates in Sesquiterpene Biosynthesis,Part II

The known sesquiterpenes that arise biosynthetically from hedycaryol are summarised. Reasonings for the assignments of their absolute configurations are discussed. The analysis provided here suggests that reprotonations at the C1=C10 double bond of hedycaryol are directed toward C1 and generally lead to 6–6 bicyclic compounds, while reprotonations at the C4=C5 double bond occur at C4 and result in 5–7 bicyclic compounds. Read more in the Review by H. Xu and J. S. Dickschat (DOI: 10.1002/chem.202200405 ).     

A Branched Diterpene Cascade: The Mechanism of Spinodiene Synthase from Saccharopolyspora spinosa

A diterpene synthase from Saccharopolyspora spinosa was found to convert geranylgeranyl diphosphate into the new natural products spinodiene A and B, accompanied by 2,7,18‐dolabellatriene. The structures and the formation mechanism of the enzyme products were investigated by extensive isotopic labelling experiments, which revealed an unusual branched isomerisation mechanism towards the neutral intermediate 2,7,18‐dolabellatriene. A Diels–Alder reaction was used to convert the main diterpene product with its rare conjugated diene moiety into formal sesterterpene alcohols.     

A Binary Bivalent Supramolecular Assembly Platform Based on Cucurbit[8]uril and Dimeric Adapter Protein 14-3-3

Interactions between proteins frequently involve recognition sequences based on multivalent binding events. Dimeric 14-3-3 adapter proteins are a prominent example and typically bind partner proteins in a phosphorylation-dependent mono- or bivalent manner. Herein we describe the development of a cucurbit[8]uril (Q8)-based supramolecular system, which in conjunction with the 14-3-3 protein dimer acts as a binary and bivalent protein assembly platform. We fused the phenylalanine–glycine–glycine (FGG) tripeptide motif to the N-terminus of the 14-3-3-binding epitope of the estrogen receptor α (ERα) for selective binding to Q8. Q8-induced dimerization of the ERα epitope augmented its affinity towards 14-3-3 through a binary bivalent binding mode. The crystal structure of the Q8-induced ternary complex revealed molecular insight into the multiple supramolecular interactions between the protein, the peptide, and Q8.     

Composition tunable cobalt-nickel and cobalt-iron alloy nanoparticles below 10?nm synthesized using acetonated cobalt carbonyl

A general organometallic route has been developed to synthesize Co(x)Ni(1-x) and Co(x)Fe(1-x) alloy nanoparticles with a fully tunable composition and a size of 4-10?nm with high yield. In contrast to previously reported synthesis methods using dicobalt octacarbonyl (Co(2)(CO)(8)), here the cobalt-cobalt bond in the carbonyl complex is first broken with anhydrous acetone. The acetonated compound, in the presence of iron carbonyl or nickel acetylacetonate, is necessary to obtain small composition tunable alloys. This new route and insights will provide guidelines for the wet-chemical synthesis of yet unmade bimetallic alloy nanoparticles. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s11051-012-0991-5) contains supplementary material, which is available to authorized users.     

Temperature Controlled Sequential Gelation in Composite Microgel Suspensions

Depending on the volume fraction and interparticle interactions, colloidal suspensions can exhibit a variety of physical states, ranging from fluids, crystals, and glasses to gels. For microgel particles made of thermoresponsive polymers, both parameters can be tuned using environmental parameters such as temperature and ionic strength, making them excellent systems to experimentally study state transitions in colloidal suspensions. Using a simple two‐step synthesis it is shown that the properties of composite microgels, with a fluorescent latex core and a responsive microgel shell, can be finely tuned. With this system the transitions between glass, liquid, and gel states for suspensions composed of a single species are explored. Finally, a suspension of two species of microgels is demonstrated, with different transition temperatures, gels in a sequential manner. Upon increasing temperature a distinct core–sheath structure is formed with a primary gel composed of the species with lowest transition temperature, which acts as a scaffold for the aggregation of the second species.