Synthesis and Toxicity Evaluation of Tire Rubber-Derived Quinones
Why this work is in the frame
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Bibliographic record
Abstract
N-(1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q), the tire rubber-derived transformation product of 6PPD, was recently discovered to cause the acute mortality of coho salmon (Oncorhynchus kisutch). Aiming to identify a potential nontoxic replacement antioxidant for 6PPD, we herein synthesized seven PPD-quinones with distinct side chains to investigate their structure-related toxicities in rainbow trout (Oncorhynchus mykiss). While 6PPD-Q exerted strong toxicity (96 h LC50 = 0.64 µg/L), toxicity was not observed for six other PPD-quinones despite their similar structures. The fish tissue concentrations of 6PPD-Q after exposure (0.8 µg/L) were comparable to the other PPD-quinones, which indicated that bioaccumulation levels were not the reason for the selective toxicity of 6PPD-Q. Hydroxylated PPD-quinones were detected as the predominant metabolites in fish tissue. Interestingly, a single major aromatic hydroxylation metabolite was detected for nontoxic PPD-quinones, but two abundant OH-6PPD-Q isomers were detected. MS2 spectra confirmed that hydroxylation occurred on the alkyl side chain for one isomer. Based on this fact, we suggested a ‘dual-action’ model wherein OH-6PPD-Q was generated by an enzyme with a high regioselectivity, which further attacks an unknown protein to cause lethality. This study reported the selective toxicity of 6PPD-Q and pinpointed the possibility for other PPDs to be applied as safe replacements of 6PPD.
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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 | 0.001 | 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 it