Nonenzymatic Pathway of PUFA Oxidation. A First-Principles Study of the Reactions of OH Radical with 1,4-Pentadiene and Arachidonic Acid
Bibliographic record
Abstract
The oxidation of polyunsaturated hydrocarbons by ·OH radical can play an important role in lipid oxidation of polyunsaturated fatty acids (PUFA) such as arachidonic acid (AA). As a prototype of this oxidation, the reaction of 1,4-pentadiene with the ·OH radical is studied using the QCISD(T)/cc-pVTZ//BH&HLYP/6-31G(d) level of theory. One of the prereaction complexes is shown to be a springboard for the indirect bisallylic hydrogen abstraction (AO), terminal (T0O), and nonterminal ·OH addition (NT0O) reactions. The enthalpies of the transition states of the AO, T0O, and NT0O reactions are found to be lower than those of the reactants, so all these reactions are expected to be fast. The nonterminal adduct is found to be reactive via two low-lying consecutive reaction channels. The first channel is a five-membered ring closing (NT1O). The second channel is bond scission, which results in an allyl radical and a vinyl alcohol (NT2O). An analogous reaction pathway in which AA takes the place of 1,4-pentadiene was explored using the ONIOM(QCISD(T)/cc-pVTZ:BH&HLYP/6-31G(d))//BH&HLYP/6-31G(d) method. The results show that the formation of the five-membered ring (AA-NT1O) is energetically favored. Our results demonstrate for the first time a possible, ab initio-based mechanism for the nonenzymatic biosynthesis of isoprostane-like structures from AA without the presence of molecular oxygen. Furthermore, the energetically low-lying bond scission channel may explain the observed formation of short fatty acids and dieneols (tautomers of unsaturated aldehydes).
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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 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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".