Radical Oxidation of the 2-Deoxyribosyl Moiety of DNA: Characterization of Unique Strand Breaks with 5′-Carboxylate Termini
Bibliographic record
Abstract
Hydroxyl radicals and other reactive species attack DNA to produce an array of nucleobase and 2-deoxyribose lesions. Here, we have characterized novel oxidatively induced modifications of the sugar moiety that arise from initial H atom abstraction at the C5′ position. In the presence of O 2, C5′-centered alkyl radicals transform into the corresponding peroxyl radicals. Ultimately, this leads to strand breaks with a modified nucleoside at the 5′-terminus. In addition to the well-known 5′-aldehyde products, we have characterized novel 5′-carboxylate products. This damage represents about 25% of the corresponding 5′-aldehyde nucleosides. We also characterized two tandem lesions, whose formation can be explained by the addition of intermediate 5′-peroxyl radicals to the C8 position of the attached purine base. The modifications were detected by UPLC-MS/MS upon exposure of DNA to ionizing radiation, Fenton reagents, and alkylperoxyl radicals.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| 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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".