Volume 10 Issue 8, August 2018

Potassium channels rapidly move K⁺ ions across cell membranes while blocking Na⁺, but how these two effects are achieved simultaneously has remained unclear. Now, extensive molecular simulations show a single mechanism that features fully dehydrated ions can explain both rapid transport and impeccable selectivity.

Enzymes can perform various biological functions because of their delicately and precisely organized structures. Now, simple inorganic nanoparticles with a rationally designed recognition capability can mimic restriction enzymes and selectively cut specific DNA sequences.

A new pyrrolysyl-tRNA synthetase/^PyltRNA (PylRS/^PyltRNA) pair that is mutually orthogonal to existing PylRS/^PyltRNA pairs has now been discovered and optimized. This system could enable the site-specific incorporation of a greater number of distinct non-canonical amino acids into a protein.

As of yet, no clear structure–performance descriptors have been developed to tune the catalytic activity of zeolitic methanol-to-olefin catalysts. Now it has been shown that introducing Lewis acidity into Brønsted acidic zeolites boosts their performance. Although Brønsted acidity is found to define propylene selectivity, Lewis acidity is responsible for prolonging lifetime.

That K⁺ channels conduct K⁺ ions at near-diffusion limited rates, but block the passage of smaller Na⁺ ions, creates an apparent contradiction. Now, atomistic simulations and free-energy calculations are used to show that both K⁺ permeation and ion selectivity are governed by the direct knock-on of completely desolvated ions in the channels’ selectivity filter.

Genome editing relies on engineered nucleases to change an organism’s DNA, but has not yet been achieved using abiotic materials. Now, chiral cysteine-capped CdTe nanoparticles are found to specifically recognize and, following photoirradiation, cut between bases T and A at the GATATC restriction site in DNA with over 90 base pairs.

Pyrrolysyl-tRNA synthetase(PylRS)/^PyltRNA_CUA pairs that lack the N-terminal domain but are active and orthogonal are discovered, and pairs that are mutually orthogonal to existing PylRS/^PyltRNA_CUA pairs are developed. Mutually orthogonal PylRS/^PyltRNA pairs are combined to genetically encode the incorporation of distinct ncAAs into proteins synthesized in E. coli.

Properly designed polyyne substrates are shown to undergo efficient cascades of thermal cycloaddition reactions initiated by (rate-limiting) benzyne formation. Proceeding through naphthyne, anthracyne or tetracyne intermediates, rapid access to highly fused, polycyclic aromatic compounds can be achieved.

Understanding the mechanism of photoconversion in fluorescent proteins is essential to optimizing applications in imaging and optogenetics. It has now been demonstrated that photoconversion in the photoswitchable protein dronpa follows a multi-step mechanism, with both chromophore and protein structural dynamics occurring on multiple timescales from picoseconds to hundreds of microseconds.

Atomic manipulation was used to control the reductive rearrangement of 1,1-dibromo alkenes to acetylenes on a NaCl surface at 5 K, and the stages of the reaction were visualized with atomic resolution using AFM. Polyynes ranging from triyne to octayne were prepared in this way, and STM was used to map their frontier orbitals and determine their transport gaps.

As a consequence of high chemical resistance and low solubility in conventional solvents, deconstructing biomass into fuels and other useful chemical building blocks remains a challenge. Now, through enzyme modification and ionic liquid solvents, it is possible to homogeneously biocatalytically convert cellulose to sugars at a rate 30 times greater than is achievable in water.

Electrophilic aromatic substitution (EAS) favours arene functionalization at positions meta to electron-withdrawing groups and para to electron-donating groups. Now, with a class of bridgehead-modified norbonene derivatives that can overcome the ortho constraint typical in palladium/norbornene catalysis, arene functionalization with site-selectivity complementary to EAS approaches can be achieved.

The [4Fe4S]²⁺ cluster-containing DNA-repair enzyme MUTYH helps safeguard the integrity of Watson–Crick base pairing and the human genetic code. The MUTYH [4Fe4S]²⁺ cluster mediates DNA redox signalling and DNA lesion identification. Now, a MUTYH pathologic variant associated with catastrophic [4Fe4S]²⁺ cluster redox degradation, impairment of DNA signalling and human colonic tumorigenesis has been identified.

A series of tungsten hydride complexes have been synthesized to mimic a proton-coupled electron transfer (PCET) step undergone by metal–hydride intermediates during solar fuel catalysis. It is shown that, by incorporating proton-accepting bases into the second coordination sphere, their PCET oxidation mechanism changes and its rate increases by several orders of magnitude.

Chiral tertiary aldols are encountered in a variety of biologically relevant molecules. Making these valuable compounds directly from unbiased ketones has proven to be extremely challenging. Now it has been shown that sub-ppm levels of in situ generated silylium-based organic Lewis acid catalysts can give quantitative product formation in very high enantiopurity through a Mukaiyama aldol reaction.

Vikki Cantrill tells the story of element 88’s discovery and how its glowing reputation eventually faded.