A Biomimetic Approach to Oxidized Sites in the Xanthine Oxidoreductase Family: Synthesis and Stereochemistry of Tungsten(VI) Analogue Complexes
Bibliographic record
Abstract
Two series of square pyramidal (SP) monodithiolene complexes, [M (VI)O 3- n S n (bdt)] (2-) and their silylated derivatives [M (VI)O 2- n S n (OSiR 3)(bdt)] (-) ( n = 0, M = Mo or W; n = 1, 2, M = W), synthesized in this and previous work, constitute the basic molecules in a biomimetic approach to structural analogues of the oxidized sites in the xanthine oxidoreductase enzyme family. Benzene-1,2-dithiolate (bdt) simulates native pyranopterindithiolene chelation in the basal plane, tungsten instead of the native metal molybdenum was employed in sulfido complexes to avoid autoreduction, and silylation models protonation. The complexes [MO 3(bdt)] (2-) and [MO 2(OSiR 3)(bdt)] (-) represent inactive sites, while [MO 2S(bdt)] (2-) and [MOS(OSiR 3)(bdt)] (-), with basal sulfido and silyloxo ligands, are the first analogues of the catalytic sites. Also prepared were [MOS 2(bdt)] (2-) and [MS 2(OSiR 3)(bdt)] (-), with basal sulfido and silyloxo ligands. Complexes are described by angular parameters which reveal occasional distortions from idealized SP toward a trigonal bipyramidal (TBP) structure arising from crystal packing forces in crystalline Et 4N (+) salts. Miminized energy structures from DFT calculations are uniformly SP and reproduce experimental structures. For example, the correct structure is predicted for [WO 2S(bdt)] (2-), whose basal and apical sulfido diastereomers are potentially interconvertible through a low-lying TBP transition state for pseudorotation. The lowest energy tautomer of the protonated form is calculated to be [WOS(OH)(bdt)] (-), with basal sulfido and hydroxo ligands. Computational and experimental structures indicate that protein sites adopt intrinsic coordination geometries rather than those dictated by protein structure and environment.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".