Volume 9 Issue 10, October 2017

Ejecting electrons from negative ions using light can create structures that very closely resemble the transition states of bimolecular reactions. Now, using this technique, trapped quantum states, or 'resonances', have been observed in a seven-atom reaction, and theory has been shown to be up to the task of capturing such complex phenomena.

DNA double helical structures are supramolecular assemblies that are typically held together by classical Watson–Crick pairing. Now, nucleotide chelation of silver ions supports an extended silver–DNA hybrid duplex featuring an uninterrupted silver array.

Water is increasingly recognized as being of paramount importance in biological processes, yet its exact role remains difficult to elucidate. Now, the motion of water molecules within and around a synthetic peptide-amphiphile nanofibre has been precisely determined, showing significant differences between its core and surface.

Glucose-responsive insulin is a therapeutic that modulates its potency, concentration or dosing relative to a patient’s dynamic glucose concentration. This Perspective summarizes some of the recent accomplishments in this field as well as discussing new computational algorithms that may aid in the development of such therapeutics.

The total synthesis of tubingensin B — an indole diterpenoid that bears a daunting chemical structure — has now been achieved. The design and evolution of this succinct total synthesis underscores the utility of long-avoided aryne intermediates for the introduction of structural motifs that have conventionally been viewed as challenging.

The transition state governs how bonds form and cleave during a reaction — its direct characterization is a long-standing challenge. Now, the F + CH₃OH → HF + CH₃O reactive surface has been studied using photoelectron velocity-map imaging spectroscopy of cryo-cooled anions, revealing vibrational Feshbach resonances and bound states supported by the post-transition-state potential well. The experiments agree well with quantum dynamical calculations.

A metallo–DNA hybrid nanowire composed only of silver-mediated base pairs has been prepared and its crystal structure resolved by X-ray diffraction. The nanowire, which is 2 nm wide and whose length reaches the μm to mm scale, holds silver ions into uninterrupted one-dimensional arrays along the DNA helical axis.

An enzyme (AspRedAm) capable of coupling carbonyls with a variety of amines in a reductive amination has now been discovered. Kinetic studies revealed that the enzyme catalysed both the imine formation step, as well as the reduction step. Structure and mutagenesis studies have highlighted essential catalytic residues and preparative scale examples have demonstrated total turnover numbers of up to 32,000.

The asymmetric Doyle–Kirmse reaction using chiral Rh(II)- or Cu(I)-catalysts provides SCF₃-containing compounds in a highly efficient and enantioselective manner. The reaction proceeds through enantioselective formation of sulfonium ylide from a diazoester and allyl- or propargyl trifluoromethyl sulfide, followed by concerted [2,3]-sigmatropic rearrangement with the transfer of chirality from sulfur to carbon.

Hexacoordinate silicon is seen often in molecular compounds, but very rarely in crystalline silicate materials. Now, reversible Si–O chemistry has been used to assemble octahedral dianionic SiO₆ building units and anthracene derivatives into crystalline microporous silicate organic frameworks that share characteristics of both covalent organic frameworks and inorganic zeolites.

Singlet fission — converting a singlet exciton to two triplet excitons — may be useful for improving photovoltaic efficiency. Ultrafast spectroscopic measurements and quantum chemical calculations have now uncovered aspects of the process critical to it occurring efficiently, including the role of intermolecular vibrations and symmetry breaking, and the location of a conical intersection on the excited-state potential-energy surface.

A DNA-based reaction network has now been developed that creates a French flag pattern with immobile and sharp borders from a shallow initial concentration gradient. The output pattern can be used to control the macroscopic organization of DNA-decorated particles thereby inducing a French flag pattern of colloidal aggregation.

Cross coupling under transition-metal-free conditions is an attractive and economic alternative to traditional transition-metal-catalysed methods. Metal-free coupling of azaallyls has now been demonstrated with vinyl bromide electrophiles, delivering allylic amines in excellent yields. Moreover, mechanistic evidence supports dual reaction pathways triggered by azaallyl anions and radicals.

Uncovering the microscopic details of protein–protein association via direct molecular dynamics (MD) simulations has been prevented by the excessive lifetimes of associated states. Now, association and dissociation for the barnase–barstar complex has been studied by adaptive high-throughput MD simulations and Markov modelling, revealing intermediate structures, energetics and kinetics on microseconds-to-hours timescales.

The assembly–disassembly–organization–reassembly (ADOR) process has recently enabled the synthesis of unusual — and sometimes previously inaccessible — inorganic materials. Further insight into its complex mechanism has now been gained that explains the unexpected formation and structure of such a zeolite.

It is still a great challenge to synthesize value-added products with two or more carbons directly from CO₂. Now, a bifunctional catalyst composed of reducible metal oxides (In₂O₃) and zeolites (HZSM-5) is prepared and yields high selectivity to gasoline-range hydrocarbons (78.6%) with a high octane number directly from CO₂ hydrogenation.

Cancer stem cells are typically refractory to conventional treatments. Now, an unprecedented mechanism has been discovered by which salinomycin and derivatives can sequester iron in lysosomes leading to cytoplasmic iron depletion and the subsequent production of reactive oxygen species that are lethal to the cell. This discovery of the importance of iron in cancer stem cell maintenance provides an opportunity for developing new therapeutics.

Dieter Ackermann explains why element 110 occupies a significant place in the superheavy corner of the periodic table.