Mechanostereochemical modulation of polymer mechanical properties.

July 28, 2026| Source: Proceedings of the National Academy of Sciences of the United States of America

Stereochemistry profoundly affects the physical and mechanical properties of polymers, illustrated by the contrast between elastic natural rubber ( cis -polyisoprene) and the stiffer, less extensible gutta-percha ( trans -isomer). Traditional stereochemistry such as tacticity and cis / trans isomerism primarily governs polymer properties based on fixed structural or conformational factors. Herein, by incorporating the mechanostereochemistry concept into polymers, we demonstrate a stereochemistry paradigm wherein dynamic isomers dictate material properties, thereby defining the unprecedented transient-stereostructure-efficacy mechanism. Specifically, we engineer two mechanically interlocked networks based on [ c 2]daisy chains, where force-triggered intramolecular motion generates mechanostereoisomers with distinct geometric configurations: [ c 2]Daisy chain 1 in MIN- 1 contracts into a fisherman's knot, whereas [ c 2]daisy chain 2 in MIN- 2 extends into a loop. Due to reduced network elasticity from the loop structure, MIN- 2 exhibits a lower modulus in large-strain shear measurements and less pronounced strain hardening in tensile tests compared to MIN- 1 . Since these mechanostereoisomers are induced by force, material properties show strain-dependent character: both networks perform similarly under small or no strain, but diverge significantly at large strains. Our work expands the conceptual boundaries of polymer stereochemistry and provides insights for designing high-performance materials through stereochemical control.

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Nature's antivenom: Combinations of conserved rattlesnake serum metalloproteinase inhibitors block the lethal action of viper venoms.

Snakebite maims or kills several hundred thousand people each year. For more than a century, treatment has relied on antivenoms derived from animals immunized with whole venoms, but their efficacy, safety, and availability are highly variable, and it is often not well understood which specific venom components must be inhibited to prevent mortality and major morbidities. New therapeutic approaches are needed. Here, we take an evolutionary approach to antivenom design inspired by the longstanding

Physical/TechAugust 4, 2026

Abrupt transition to irreversible damage in the overdrafted Sacramento Valley aquifer system.

Groundwater extraction decreases water pressure in aquifer systems, causing reversible or irreversible deformation of the water-bearing layers that manifests as recoverable or permanent displacements of the land surface, respectively. Detecting and forecasting when and where an aquifer system transitions from a reversible, poroelastic regime, to an irreversible, inelastic regime remains a crucial challenge given the complex, heterogeneous nature of aquifer systems. Here we leverage high-resoluti

Physical/TechJuly 28, 2026

Synergistic action of different molecular mechanisms causes striking levels of insecticide resistance in the malaria vector Anopheles gambiae .

Intensifying insecticide resistance in the malaria vector Anopheles gambiae poses a serious threat to the progress achieved the last decades in reducing malaria deaths in Africa. The genetic basis of insecticide resistance is often complex, involving multiple genes and mutations. However, we still lack a clear understanding of how each mechanism contributes to overall resistance and how highly resistant phenotypes arise. In this study, we generated a suite of transgenic An. gambiae strains carry

Physical/TechJuly 28, 2026

There is no free benchmark: An institutional view of legal AI benchmarking.

Despite substantial excitement around the use of AI in law, little information exists on the performance and associated risks of the domain's widely marketed tools. Recent work, for instance, has demonstrated the significant potential for "hallucinations"-wherein models make up facts, law, and precedent-leading Chief Justice Roberts to spotlight this risk in his annual report on the judiciary. We argue that there is a need for public AI benchmarking in law. First, relative to other AI applicatio

Physical/TechJuly 28, 2026

A phosphorylation cascade involving ZmSnRK2.10-ZmRIPK2-ZmWRKY38 attenuates drought response by derepressing ZmSUS2 in maize.

Drought stress severely limits crop productivity, with transcription factors (TFs) playing pivotal roles in plant adaptation. Here, we identify the maize TF ZmWRKY38 as a positive regulator of drought tolerance. CRISPR/Cas9-mediated knockout of ZmWRKY38 increased plant sensitivity to drought compared with the wild type. We demonstrate that ZmWRKY38 binds to the promoter of the sucrose synthase gene ZmSUS2 and represses its transcription. Conversely, ZmSUS2 functions as a negative regulator of dr