Gaseous Bradykinin and Its Singly, Doubly, and Triply Protonated Forms: A First-Principles Study
Bibliographic record
Abstract
The conformers of gaseous bradykinin, BK, (Arg(1)-Pro(2)-Pro(3)-Gly(4)-Phe(5)-Ser(6)-Pro(7)-Phe(8)-Arg(9)) and its protonated forms, [BK + H](+), [BK + 2H](2+), and [BK + 3H](3+), were examined theoretically using a combination of the Merck molecular force field, Hartree-Fock, and density functional theory. Neutral BK, [BK + H](+), and [BK + 2H](2+) exist in zwitterionic forms that are stabilized by internal solvation and have compact structures; [BK + 3H](3+) differs by the absence of a salt bridge and adopts an elongated form. The common structural feature in all four BK species is a beta-turn in the Ser(6)-Pro(7)-Phe(8)-Arg(9) sequence. The gas-phase basicity of [BK + H](+) estimated from the calculated protonation energy is in accord with published experimental basicity; population-weighted collision cross-sections of the three ionic forms are in agreement with experimental cross-sections in the literature.
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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".