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We demonstrate the ability of a non-heme iron containingl-lysine dioxygenase to perform sequential oxidation on its native substrate and computationally explore structural elements that promote this reactivity. 

Abstract Highly selective C−H functionalization remains an ongoing challenge in organic synthetic methodologies. Biocatalysts are robust tools for achieving these difficult chemical transformations. Biocatalyst engineering has often required directed evolution or structure‐based rational design campaigns to improve their activities. In recent years, machine learning has been integrated into these workflows to improve the discovery of beneficial enzyme variants. In this work, we combine a structure‐based self‐supervised machine learning framework, MutComputeX, with classical molecular dynamics simulations to down select mutations for rational design of a non‐heme iron‐dependent lysine dioxygenase, LDO. This approach consistently resulted in functional LDO mutants and circumvents the need for extensive study of mutational activity before‐hand. Our rationally designed single mutants purified with up to 2‐fold higher expression yields than WT and displayed higher total turnover numbers (TTN). Combining five such single mutations into a pentamutant variant, LPNYI LDO, leads to a 40 % improvement in the TTN (218±3) as compared to WT LDO (TTN=160±2). Overall, this work offers a low‐barrier approach for those seeking to synergize machine learning algorithms with pre‐existing protein engineering strategies. 

The effects of growth conditions on the chemistry, structure, electrical leakage, dielectric response, and ferroelectric behavior of Ba 1−x TiO y thin films are explored. Although single-phase, coherently-strained films are produced in all cases, small variations in the laser fluence during pulsed-laser deposition growth result in films with chemistries ranging from BaTiO 3 to Ba 0.93 TiO 2.87 . As the laser fluence increases, the films become more barium deficient and the out-of-plane lattice parameter expands (as much as 5.4% beyond the expected value for Ba 0.93 TiO 2.87 films). Stoichiometric BaTiO 3 films are found to be three orders of magnitude more conducting than Ba 0.93 TiO 2.87 films and the barium-deficient films exhibit smaller low-field permittivity, lower loss tangents, and higher dielectric maximum temperatures. Although large polarization is observed in all cases, large built-in potentials (shifted loops) and hysteresis-loop pinching are present in barium-deficient films – suggesting the presence of defect dipoles. The effects of these defect dipoles on ferroelectric hysteresis are studied using first-order reversal curves. Temperature-dependent current–voltage and deep-level transient spectroscopy studies reveal at least two defect states, which grow in concentration with increasing deficiency of both barium and oxygen, at ∼0.4 eV and ∼1.2 eV above the valence band edge, which are attributed to defect–dipole complexes and defect states, respectively. The defect states can also be removed via ex post facto processing. Such work to understand and control defects in this important material could provide a pathway to enable better control over its properties and highlight new avenues to manipulate functions in these complex materials.