DFT Computational Study of the Methanolytic Cleavage of 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 theory study of the cleavage of a DNA model [p-nitrophenyl methyl phosphate (2)] and two RNA models [p-nitrophenyl 2-hydroxypropyl phosphate (3) and phenyl 2-hydroxypropyl phosphate (4)] promoted by the dinuclear Zn((II)) complex of 1,3-bis(1,5,9-triazacyclododec-1-yl)propane formulated with a bridging methoxide (1a) was undertaken to determine possible mechanisms for the transesterification processes that are consistent with experimental data. The initial substrate-bound state of 2:1a or 3:1a has the two phosphoryl oxygens bridging Zn((II))1 and Zn((II))2. For each of 2 and 3, four possible mechanisms were investigated, three of which were consistent with the overall free energy for the catalytic cleavage step for each substrate. The computations revealed various roles for the metal ions in the three mechanisms. These encompass concerted or stepwise processes, where the two metal ions with associated alkoxy groups [Zn((II))1:((-)OCH3) and Zn((II))1:((-)O-propyl)] play the role of a direct nucleophile (on 2 and 3, respectively) or where Zn((II))1:((-)OCH3) can act as a general base to deprotonate an attacking solvent molecule in the case of 2 or the attacking 2-hydroxypropyl group in the case of 3. The Zn((II))2 ion can serve as a spectator (after exerting a Lewis acid role in binding one of the phosphates' oxygens) or play active additional roles in providing direct coordination of the departing aryloxy group or positioning a hydrogen-bonding solvent to assist the departure of the leaving group. An important finding revealed by the calculations is the flexibility of the ligand system that allows the Zn-Zn distance to expand from ~3.6 Å in 1a to over 5 Å in the transforming 2:1a and 3:1a 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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".