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Ethylene formation by the ethylene-forming enzyme (EFE) and 1-aminocyclopropane-1-carboxylate oxidase (ACCO). 

The non-heme Fe( ii ) and 2-oxoglutarate (2OG) dependent ethylene-forming enzyme (EFE) catalyzes both ethylene generation and l -Arg hydroxylation. Despite experimental and computational progress in understanding the mechanism of EFE, no EFE variant has been optimized for ethylene production while simultaneously reducing the l -Arg hydroxylation activity. In this study, we show that the two l -Arg binding conformations, associated with different reactivity preferences in EFE, lead to differences in the intrinsic electric field (IntEF) of EFE. Importantly, we suggest that applying an external electric field (ExtEF) along the Fe–O bond in the EFE·Fe( iii )·OO − ˙·2OG· l -Arg complex can switch the EFE reactivity between l -Arg hydroxylation and ethylene generation. Furthermore, we explored how applying an ExtEF alters the geometry, electronic structure of the key reaction intermediates, and the individual energy contributions of second coordination sphere (SCS) residues through combined quantum mechanics/molecular mechanics (QM/MM) calculations. Experimentally generated variant forms of EFE with alanine substituted for SCS residues responsible for stabilizing the key intermediates in the two reactions of EFE led to changes in enzyme activity, thus demonstrating the key role of these residues. Overall, the results of applying an ExtEF indicate that making the IntEF of EFE less negative and stabilizing the off-line binding of 2OG is predicted to increase ethylene generation while reducing l -Arg hydroxylation. 

Abstract Many living tissues achieve functions through architected constituents with strong adhesion. An Achilles tendon, for example, transmits force, elastically and repeatedly, from a muscle to a bone through staggered alignment of stiff collagen fibrils in a soft proteoglycan matrix. The collagen fibrils align orderly and adhere to the proteoglycan strongly. However, synthesizing architected materials with strong adhesion has been challenging. Here we fabricate architected polymer networks by sequential polymerization and photolithography, and attain adherent interface by topological entanglement. We fabricate tendon-inspired hydrogels by embedding hard blocks in topological entanglement with a soft matrix. The staggered architecture and strong adhesion enable high elastic limit strain and high toughness simultaneously. This combination of attributes is commonly desired in applications, but rarely achieved in synthetic materials. We further demonstrate architected polymer networks of various geometric patterns and material combinations to show the potential for expanding the space of material properties.