Generation of 2′-Deoxyadenosine <i>N</i><sup>6</sup>-Aminyl Radicals from the Photolysis of Phenylhydrazone Derivatives
Bibliographic record
Abstract
Nitrogen-centered radicals are major species generated by the addition of hydroxyl radicals and the one-electron oxidation of adenine derivatives. Aminyl radicals are also generated in the decomposition of adenine chloramines upon reaction of hypochlorite. Here, we report the photochemistry of modified 2'-deoxyadenosine (dAdo) containing photoactive hydrazone substituents as a model to investigate the chemistry of dAdo N(6)-aminyl radicals. Derivatives of dAdo containing a phenylhydrazone moiety at N6 displayed UV absorption between 300 and 400 nm. Upon UV photolysis in the presence of a H-donor, that is, glutathione, two major products were formed, dAdo and benzaldehyde, indicating efficient homolytic cleavage to dAdo N(6)-aminyl radicals and benzylidene iminyl radicals. dAdo N(6)-phenylhydrazone was photolyzed in the presence of a molar excess of nonmodified dAdo to mimic the reactions taking place in DNA, and the major photoproducts were identified by high-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance. The formation of 2-(benzylideneamino)-2'-deoxyadenosine as well as a more extensive oxidation product may be explained by the recombination of initial dAdo N(6)-aminyl and benzylidene iminyl radicals. The formation of 2'-deoxyinosine may be explained by hydrolytic deamination of dAdo N(6)-aminyl radicals. Interestingly, a dimeric product containing two dAdo moieties was identified in the photolysis mixture. The present studies demonstrate the ability of dAdo N(6)-aminyl radicals to undergo H-abstraction to give dAdo, deamination to give 2'-deoxyinosine, and addition to the adenine moiety to give dimers.
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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".