Cysteine Radical/Metal Ion Adducts: A Gas‐Phase Structural Elucidation and Reactivity Study
Bibliographic record
Abstract
Abstract The formation and investigation of sulfur‐based cysteine radicals cationized by a group 1A metal ion or Ag+ in the gas phase are reported. Gas‐phase ion–molecule reactions (IMR) and infrared multiple‐photon dissociation (IRMPD) spectroscopy revealed that the Li+, Na+, and K+ adducts of the cysteine radical remain S‐based radicals as initially formed. Theoretical calculations for the three alkali metal ions found that the lowest‐energy isomers are Cα‐based radicals, but they are not observed experimentally owing to the barriers associated with the hydrogen‐atom transfer. A mechanism for the S‐to‐Cα radical rearrangement in the metal ion complexes was proposed, and the relative energies of the associated energy barriers were found to be Li+>Na+>K+ at all levels of theory. Relative to the B3LYP functional, other levels of calculation gave significantly higher barriers (by 35–40 kJ mol−1 at MP2 and 44–47 kJ mol−1 at the CCSD level) using the same basis set. Unlike the alkali metal adducts, the cysteine radical/Ag+ complex rearranged from the S‐based radical to an unreactive species as indicated by IMRs and IRMPD spectroscopy. This is consistent with the Ag+/cysteine radical complex having a lower S‐to‐Cα radical conversion barrier, as predicted by the MP2 and CCSD levels of theory.
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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) | 0.002 | 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".