Unambiguous Determination of Protein Arginine Ionization States in Solution by NMR Spectroscopy
Bibliographic record
Abstract
Abstract Because arginine residues in proteins are expected to be in their protonated form almost without exception, reports demonstrating that a protein arginine residue is charge‐neutral are rare and potentially controversial. Herein, we present a 13C‐detected NMR experiment for probing individual arginine residues in proteins notwithstanding the presence of chemical and conformational exchange effects. In the experiment, the 15Nη and 15Nϵ chemical shifts of an arginine head group are correlated with that of the directly attached 13Cζ. In the resulting spectrum, the number of protons in the arginine head group can be obtained directly from the 15N–1H scalar coupling splitting pattern. We applied this method to unambiguously determine the ionization state of the R52 side chain in the photoactive yellow protein from Halorhodospira halophila. Although only three Hη atoms were previously identified by neutron crystallography, we show that R52 is predominantly protonated in solution.
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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) | 0.001 | 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 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".