How to make an oscillator

A cell-free approach reveals how genetic circuits can produce robust oscillations of proteins and other components

Directional interactions in semiflexible single-chain polymer folding

Precise control over folded conformations of synthetic polymers is highly desirable in the development of functional nanomaterials for diverse applications. Introducing monomers capable of strong intramolecular hydrogen bonding is a promising route to achieve this control. In the present work we report the use of Wang–Landau Monte Carlo simulations of coarse-grained copolymers to explore the design parameters of these systems on their pathway to collapse. The highly directional nature of hydrogen-bonded supramolecular interactions is modelled by a directional non-bonded potential while a harmonic bending potential is used to take into account the flexibility of the polymer chain, thus making it possible to look at the interplay of both factors. The introduction of directional interactions in the copolymer chain leads to a sharper coil-globule collapse when compared to homopolymers composed of isotropic interacting beads only. Simultaneously, some of the stiffness-dependent structural properties become exacerbated when directional beads are present. Finally, from the heat capacity profiles for the different chain stiffness values we are able to distinguish the prevalence of the collapse of the backbone for highly flexible chains, while as chain stiffness increases folding of the co-polymer due to the directional interactions becomes the dominant feature

Modulating the Nucleated self-assembly of Tri-beta3-peptides using cucurbit[n]urils

The modulation of the hierarchical nucleated self-assembly of tri-β3-peptides has been studied. β3-Tyrosine provided a handle to control the assembly process through host-guest interactions with CB[7] and CB[8]. By varying the cavity size from CB[7] to CB[8] distinct phases of assembling tri-β3-peptides were arrested. Given the limited size of the CB[7] cavity, only one aromatic β3-tyrosine can be simultaneously hosted and, hence, CB[7] was primarily acting as an inhibitor of self-assembly. In strong contrast, the larger CB[8] can form a ternary complex with two aromatic amino acids and hence CB[8] was acting primarily as cross-linker of multiple fibers and promoting the formation of larger aggregates. General insights on modulating supramolecular assembly can lead to new ways to introduce functionality in supramolecular polymers

Materials science: Supramolecular polymers

Most polymers consist of long molecular chains made up of many units connected by covalent bonds — but supramolecular polymers are different. The strikingly dynamic properties of these materials arise from the reversible bonds that hold their chains together, and open up the prospect of many new applications

Eye Metrics for Task-Dependent Automation

Future air traffic is expected to grow increasingly, opening up a gap for task dependent automation and adaptive interfaces, helping the Air Traffic Controller to cope with fluctuating workloads. One of the challenging factors in the application of such intelligent systems concerns the question what the operator is doing in order to optimize support and minimize automation surprises. This study questions whether eye metrics are able to determine what task the operator is engages in. We therefore examined A) if the eye-path would differ for three different ATC tasks and B) whether this effect can be quantified with six eye-metrics. In an experiment, the six eye-metrics were calculated and used as a dependent variable. The results show that some tasks can be inferred by eye movement metrics and other metrics infer workload, although none inferred by both task and workload. Copyright 2014 ACM

Supraomolecular polymers

In the past few decades, supramolecular polymers have emerged as novel materials with a wide variety of different functions. In this essay we reflect on the history of supramolecular polymers, their function in various applications and the challenges to be met in the near future

Materials science: Supramolecular polymers

Most polymers consist of long molecular chains made up of many units connected by covalent bonds — but supramolecular polymers are different. The strikingly dynamic properties of these materials arise from the reversible bonds that hold their chains together, and open up the prospect of many new applications