Oxidatively Generated Nucleobase Modifications in Isolated and Cellular<scp>DNA</scp>
Bibliographic record
Abstract
Abstract The main oxidation reactions of the main pyrimidine bases (thymine and cytosine) and purine bases (adenine and guanine), and 5‐methylcytosine mediated by hydroxyl radical (·OH) as well as one‐electron oxidants and singlet oxygen (1O2) leading to about 80 single‐oxidized‐type lesions are reported and the mechanism of their formation critically discussed. In addition, a few complex modifications including tandem base modifications involving either carbon‐centered radical or peroxyl radicals derived from radical oxidation of pyrimidine bases are also described. One may add modifications that arise from initial OH‐mediated hydrogen atom abstraction at C5 and C4 of the 2‐deoxyribose moiety of DNA giving rise to purine 5′,8‐cyclonucleosides and four diastereomeric aldehyde adducts to opposite cytosine bases in double‐stranded DNA, respectively. With the high level of product identification and thanks to the high sensitivity of high performance liquid chromatography (HPLC)‐electrospray ionization‐tandem mass spectrometry analysis, relevant information is gained on the formation of oxidation products in cells. Thus, 12 single and 5 complexes oxidatively generated base lesions have been detected in cellular DNA on exposure to1O2, γ rays and high‐intensity ultraviolet C (UVC) laser pulses. The information thus gained is strongly supportive of the oxidation mechanisms that were inferred from mechanistic studies on model systems in aerated aqueous solutions.
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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".