Active camouflage from a polymer: Human skin is soft and compliant, but it can quickly become stiff when deformed to prevent injury. Chameleon skin can change color when the animal goes from a relaxed to an excited state. Although these properties can be captured individually in synthetic materials, the combination of different dynamic responses can be hard to control. Vatankhah-Varnosfaderani et al. created triblock copolymers of the ABA variety, where the A blocks have a linear structure and the B blocks are like bottlebrushes. When strained, these polymers stiffened like human skin and changed color, thus giving the materials a range of adaptive properties. Science , this issue p. 1509

3D mapping of crystal and nanostructure orientation shows that bone contains a mineral fraction not aligned with the nanostructure.

Chemists aim to meet modern sustainability, health, and safety requirements by replacing conventional solvents with deep eutectic solvents (DESs). Through large melting point depressions, DESs may incorporate renewable solids in task-specific liquids. Yet, DES design is complicated by complex molecular interactions and a lack of comprehensive property databases. Even measuring pure component melting properties can be challenging, due to decomposition before melting. Here we overcame the decomposition of the quintessential DES constituent, choline chloride (ChCl). We measured its enthalpy of fusion (13.8 ± 3.0 kJ ⋅ mol) and melting point (687 ± 9 K) by fast scanning calorimetry combined with micro-XRD and high-speed optical microscopy. Our thermodynamically coherent fusion properties identify ChCl as an ionic plastic crystal and demonstrate negative deviations from ideal mixing for ChCl—contradicting previous assumptions. We hypothesise that the plastic crystal nature of ammonium salts governs their resilience to melting; pure or mixed. We show that DESs based on ionic plastic crystals can profit from (1) a low enthalpy of fusion and (2) favourable mixing. Both depress the melting point and can be altered through ion selection. Ionic plastic crystal-based DESs thus offer a platform for task-specific liquids at a broad range of temperatures and compositions.

Cyt1Aa is the one of four crystalline protoxins produced by mosquitocidal bacteriumBacillus thuringiensis israelensis(Bti) that has been shown to delay the evolution of insect resistance in the field. Limiting our understanding ofBtiefficacy and the path to improved toxicity and spectrum has been ignorance of how Cyt1Aa crystallizes in vivo and of its mechanism of toxicity. Here, we use serial femtosecond crystallography to determine the Cyt1Aa protoxin structure from sub-micron-sized crystals produced inBti. Structures determined under various pH/redox conditions illuminate the role played by previously uncharacterized disulfide-bridge and domain-swapped interfaces from crystal formation inBtito dissolution in the larval mosquito midgut. Biochemical, toxicological and biophysical methods enable the deconvolution of key steps in the Cyt1Aa bioactivation cascade. We additionally show that the size, shape, production yield, pH sensitivity and toxicity of Cyt1Aa crystals grown inBtican be controlled by single atom substitution.