Quantum Coulombic Interactions Mediate Free Radical Control in Radical SAM Viperin/RSAD2
Bibliographic record
Abstract
There are thousands of radical S -adenosylmethionine (rSAM) enzymes capable of catalyzing over 80 distinct reactions, yet their use in biotechnological applications is limited, primarily due to a lack of understanding of how these enzymes control highly reactive radical intermediates. Here, we show that little-known quantum Coulombic interactions are, in part, responsible for free radical control in rSAM enzyme Viperin/RSAD2, one of the few radical SAM enzymes expressed in humans. Using molecular dynamics and high-level extensive multistate broken-symmetry quantum mechanical/molecular mechanics calculations (QM/MM), we elucidated both the mechanism and radical control in catalysis, identifying a key step characterized by the formation of an unusual metastable deprotonated ribose radical intermediate. This intermediate is thermodynamically stabilized by spin-charge exchange–correlation interactions─a quantum Coulombic effect. The magnitude of this stabilization is such that the radical displays acidity two to six p K a units lower than that of closed-shell ribose. Given the omnipresence of charges in biological systems, these interactions potentially represent a universal mechanism for stabilizing and controlling highly reactive radical intermediates across radical enzymes, opening new avenues for enzymatic engineering and biotechnological applications.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.002 |
| 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 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".