Evidence for Anisotropic Coupling between the Protein Environment and the Copper Site in Azurin from Resonance Raman Spectroscopy
Bibliographic record
Abstract
A key problem in biological electron transfer is the independent measurement of the parameters upon which the rate constant for electron transfer depends. In this paper, we report evidence that quantitative resonance Raman spectroscopy may be such an independent probe of the electronic coupling parameter in proteins. The resonance Raman cross-sections of four species of azurin have been measured throughout the ca. 600-nm absorption band. The total resonance Raman intensity, as quantified by the cross-sections, is very similar for the four azurins in the 200−700 cm -1 region. However, the resonance Raman intensity is distributed differentially among the vibrational modes, sometimes also accompanied by small frequency shifts. Correlations are attempted between this re-distribution of resonance Raman intensity and Cu−S bond length, Cu out-of-plane distance, backbone structure, and protein environment. Of these four parameters, the only significant correlation exists with the protein environment. A detailed analysis of the residues within 10 Å of the copper site demonstrates a strong, anisotropic coupling between the copper site and Trp48, a residue previously implicated in intramolecular electron transfer pathways of azurin.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.001 |
| 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".