Volume 7 Issue 3, March 2015

The ability of enzymes to direct the synthesis of complex natural products from simple starting materials is epitomized by terpene biosynthesis. Now, a supramolecular catalyst has been shown to mimic some of the reactivity of this process.

In their natural environment, membrane proteins are surrounded by lipids, but the effect that the lipids have on the proteins is not easy to assess. Now, controlling the extent of delipidation has enabled the study of these interactions.

Replication of long nucleic acid sequences was required for the evolution of biological complexity during the origin of life; however, short sequences are normally better replicators than long ones. A common physical environment now provides a simple mechanism to reverse this trend and enables long sequences to flourish.

The structure of liquid water is intensely studied, but it is not clear what happens to it when a surface is introduced. Now with the aid of X-ray spectroscopy it has been found that water molecules at the interface with a gold electrode have a different structure than in the bulk.

Nanoporous carbon is attractive for separation purposes, but its use for low-pressure water capture has remained a challenge. Carbon cuboids have now been prepared that combine high hydrophilicity with a microporous architecture suitable for efficient trapping of atmospheric water vapour.

A tail-to-head terpene cyclization, which is hard to control in solution, has now been catalysed inside a supramolecular structure. Evidence indicates that a direct isomerization of a geranyl cation to the cisoid-isomer, which so far was considered unlikely in the biosynthesis, is feasible in this system.

How complex nucleic acids originally formed, despite dilution and degradation reactions, is not clear. Thermal gradients in rock pores have now been shown to be capable of trapping and thermo-cycling genetic polymers during replication. In this system long oligonucleotide strands are seen to outcompete short strands — a prerequisite for the evolution of replicating systems towards increasing complexity.

Understanding the intrinsic electronic properties of building blocks in conjugated materials can provide powerful design guidelines to control charge transport, such as tuning the nature of the charge carriers. Now, single-molecule transport studies of a family of oxidized oligothiophenes have shown that their molecular length determines the dominant carrier type.

Creating molecular components with controllable electronic properties is crucial to the realization of nanoscale devices. Now, a single-molecule conductance switch that operates through a stereoelectronic effect has been developed. The sub-ångström control of a scanning tunnelling microscope is used to switch reversibly between two distinct sets of rotational isomers, which differ greatly in their electronic character.

Charge transport in molecular systems is typically through coherent tunnelling over a short distance or incoherent hopping over a long distance. An intermediate regime between those two transport mechanisms has now been found for DNA systems with stacked guanine–cytosine sequences.

A lack of general methods for making multisubstituted benzene derivatives means that only a small fraction of the huge number of possible structures based on this ubiquitous building block have been explored. Now, a programmed synthesis of hexaarylbenzenes using C–H activation, cross-coupling and [4 + 2] cycloaddition reactions has been developed that can also be applied to tetraarylnaphthalenes and pentaarylpyridines.

A seven-step total synthesis of the axially chiral, dimeric tetrahydroxanthone natural product rugulotrosin A is described. The synthesis employs a one-pot Suzuki coupling/dimerization to generate the 2,2′-biaryl linkage using point-to-axial chirality transfer. Computational studies are described that rationalize the observed atropselectivity.

A method to identify pairs of ligands that simultaneously bind to a target protein has been developed. The method uses two DNA-encoded chemical sub-libraries that self-assemble to form stable dual-display structures, and an encoding system that can be decoded by DNA sequencing and enables both ligands to be identified.

The explosion of alkali metals in water is a typical high-school chemistry experiment, but its mechanism is not fully understood. Using high-speed cameras and molecular simulations it is now shown that a key early step in this reaction is the migration of electrons from the alkali metal into water, leading to a charging of the metal's surface and subsequent Coulomb explosion.

Defining the lipid composition that exists around a membrane protein complex in natural bilayers is a challenging task. Now, key lipids that are important for the structure and function of an ABC transporter have been revealed by systematically removing layers of lipids, and using mass spectrometry to monitor those that remained closely associated with the membrane protein.

Wojciech Grochala describes how the oldest, lightest and most abundant element in the universe continues to play an essential role on today's Earth.

The miniaturization of electronic devices that use silicon-based technology will soon reach a limit and if devices are to continue getting smaller, scientists must harness the electronic properties of single molecules. A collection of Articles in this Focus highlights recent progress in the understanding and control of charge transport through single molecules.