DFT Computational\nStudy of the Methanolytic Cleavage\nof DNA and RNA Phosphodiester Models Promoted by the Dinuclear Zn<sup>(II)</sup> Complex of 1,3-Bis(1,5,9-triazacyclododec-1-yl)propane
Bibliographic record
Abstract
A density functional\ntheory study of the cleavage of a DNA model\n[<i>p</i>-nitrophenyl methyl phosphate (<b>2</b>)]\nand two RNA models [<i>p</i>-nitrophenyl 2-hydroxypropyl\nphosphate (<b>3</b>) and phenyl 2-hydroxypropyl phosphate (<b>4</b>)] promoted by the dinuclear Zn<sup>(II)</sup> complex of\n1,3-bis(1,5,9-triazacyclododec-1-yl)propane formulated with a bridging\nmethoxide (<b>1a</b>) was undertaken to determine possible mechanisms\nfor the transesterification processes that are consistent with experimental\ndata. The initial substrate-bound state of <b>2</b>:<b>1a</b> or <b>3</b>:<b>1a</b> has the two phosphoryl oxygens\nbridging Zn<sup>(II)</sup><sub>1</sub> and Zn<sup>(II)</sup><sub>2</sub>. For each of <b>2</b> and <b>3</b>, four possible mechanisms\nwere investigated, three of which were consistent with the overall\nfree energy for the catalytic cleavage step for each substrate. The\ncomputations revealed various roles for the metal ions in the three\nmechanisms. These encompass concerted or stepwise processes, where\nthe two metal ions with associated alkoxy groups [Zn<sup>(II)</sup><sub>1</sub>:(<sup>−</sup>OCH<sub>3</sub>) and Zn<sup>(II)</sup><sub>1</sub>:(<sup>−</sup>O-propyl)] play the role of a direct\nnucleophile (on <b>2</b> and <b>3</b>, respectively) or\nwhere Zn<sup>(II)</sup><sub>1</sub>:(<sup>−</sup>OCH<sub>3</sub>) can act as a general base to deprotonate an attacking solvent molecule\nin the case of <b>2</b> or the attacking 2-hydroxypropyl group\nin the case of <b>3</b>. The Zn<sup>(II)</sup><sub>2</sub> ion\ncan serve as a spectator (after exerting a Lewis acid role in binding\none of the phosphates’ oxygens) or play active additional roles\nin providing direct coordination of the departing aryloxy group or\npositioning a hydrogen-bonding solvent to assist the departure of\nthe leaving group. An important finding revealed by the calculations\nis the flexibility of the ligand system that allows the Zn–Zn\ndistance to expand from ∼3.6 Å in <b>1a</b> to over\n5 Å in the transforming <b>2</b>:<b>1a</b> and <b>3</b>:<b>1a</b> complexes during the catalytic event.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.025 | 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".