Stabilization of an Unusual Tautomer of Guanine: Photoionization of Al−Guanine and Al−Guanine−(NH<sub>3</sub>)<i><sub>n</sub></i>
Bibliographic record
Abstract
Photoionization efficiency spectra of gas-phase Al−guanine−(NH 3 ) n, 0 ≤ n ≤ 2, have been measured in the 210−270 nm range. Within error the ionization energies, 4.65 ± 0.08, 4.6 ± 0.1, and 4.5 ± 0.2 eV for n = 0, 1, and 2, respectively, are equivalent. This result is explained in terms of molecular geometries in which NH 3 associates with the guanine constituent of Al−guanine specifically. The onset of signal in the Al−guanine photoionization efficiency spectrum is found to shift from 5.6 ± 0.1 to 4.65 ± 0.08 eV upon introduction of NH 3 to the He carrier gas. The shift is indicative of formation of vastly different amounts of distinct isomers of Al−guanine in the presence or absence of NH 3 . The geometries, ionization energies, and heats of formation of the isomers have been determined using DFT calculations benchmarked against the experimental ionization energies. The most stable isomer is one of an Al atom complexed to an unusual tautomer of guanine in which, effectively, a proton has been transferred from the six-membered ring to the five-membered ring. To our knowledge, this is the first demonstration of the existence of this tautomer of guanine.
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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) | 0.001 | 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".