Volume 4 Issue 11, November 2012

A dramatic switch of reactivity — from hydroquinone oxidation to N-hydroxylation — can be achieved through the rational engineering of a de novo-designed di-iron protein. Four specific amino-acid mutations spread throughout the first, second and third coordination shells result in a million-fold increase in the relative rate of these two reactions.

A classic calcium aluminate has been modified to create an inorganic electride that can be used as a promoter of the catalytic synthesis of ammonia.

Switchable molecular materials generally alternate between two different states that are both stable in identical conditions. A magnetic molecular system is now available that allows switching between three different phases of the same compound.

This Review describes the general trends and implications of heterogeneities within individual catalyst particles as observed by modern spatiotemporal spectroscopy. It discusses how catalytic materials have been found to display heterogeneities in structure, composition and reactivity in space and time. The implications of these findings for future catalyst design are also described.

Porous solids are well suited to the capture of environmentally harmful gases, but further understanding of the solid–gas interactions involved is required. Combining dynamic and static characterization with modelling, researchers have now described how a metal–organic framework binds CO₂ and SO₂ selectively through hydroxyl groups — rather than amine ones as typically featured.

A demonstration of simple sugar synthesis from single carbon feedstocks would provide significant support for the involvement of RNA in the origin of life. Here, hydrogen cyanide is shown to feed a cyanocuprate photoredox cycle that ultimately provides both the starting material and the reducing power necessary for a Killiani–Fischer-type sugar synthesis.

Representing the first successful rational reprogramming of function in a de novo protein, the reactivity of a designed di-iron carboxylate protein from the Due Ferri family was altered from hydroquinone oxidation to arylamine N-hydroxylation through the introduction of a critical third histidine ligand in the active site.

Single-molecule experiments reveal substantial molecule-to-molecule variation in the Mg²⁺-induced isomerization dynamics of Holliday junctions (HJs). Effective ergodicity breaking of time trajectories results in the partitioning of HJ dynamics into multiple clusters. The observed dynamical heterogeneity is a consequence of various internal multiloop conformations that are frozen by Mg²⁺ ions.

Sesquiterpenes are biosynthesized from linear isoprenols through the intermediacy of multiple, high-energy carbocations. Here a strategy is demonstrated for mimicking these reactions in bulk solvent to yield strained, acid-labile terpenes. Key to the success of these reactions is the sequestration of the counteranion away from the reactive carbocation, a strategy that should enable further study of challenging polycyclizations.

Bistable materials, which exist in either one of two phases under identical conditions, are intriguing both from a fundamental perspective and for their practical applications. A cyanide-bridged [CoFe] coordination chain has now been prepared that shows both magnetic and electric bistabilities in the same temperature range, undergoing thermo- and photo-induced conversions between insulating, semiconducting and single-chain magnet-type phases.

A family of robust β-sheet macrocycles that can display a variety of heptapeptide sequences from different amyloid proteins is introduced. These amyloid β-sheet mimics can be tailored to antagonize aggregation of the proteins, thereby reducing the toxicity associated with diseases such as Alzheimer's.

Methods that fix atmospheric nitrogen to ammonia under mild conditions could offer a more environmentally benign alternative to the Haber–Bosch process. Now, a Ru-loaded electride, [Ca₂₄Al₂₈O₆₄]⁴⁺(e⁻)₄, is reported that acts as an efficient electron donor and reversible hydrogen store, and is demonstrated to function as an efficient catalyst for ammonia synthesis.

RNA compartmentalization is essential for cellular functions and may have played a pivotal role in the emergence of life. However, the consequences of compartmentalization on RNA catalysis have been largely unexplored. Here, partitioning of catalytic RNA in a two-phase aqueous polymer solution increased local RNA concentration, enhancing ribozyme kinetics.

Heterogeneous catalysts are generally more readily recycled than homogeneous catalysts, but the latter are more easily modified to tune reactivity and selectivity. Here, the dendrimer coating of gold nanoparticle catalysts is shown to be a surrogate for the ligands of homogeneous catalysts. Tuning of product distribution and reaction selectivity is possible when these catalysts are employed in a fixed-bed flow reactor.

Gregory Girolami recounts how element 76 beat a close competitor to the title of densest known metal and went on to participate in Nobel Prize-winning reactions.