Metal Ion Facilitated Dissociation of Heme from <i>b</i>-Type Heme Proteins
Bibliographic record
Abstract
Addition of Ni(2+), Cu(2+), or Zn(2+) (10-40 equiv) to metMb in sodium bicarbonate buffer (25 degrees C) at alkaline pH (7.8-9.5) results in a time-dependent (2-6 h) change in the electronic absorption spectrum of the protein that is consistent with dissociation of the heme from the active site and that can be largely reversed by addition of EDTA. Similar treatment of cytochrome b(5), indoleamine 2,3-dioxygenase, and cytochrome P450(cam) (in the presence or absence of camphor) produces a similar spectroscopic response. Elution of metMb treated with Ni(2+) in this manner over an anion exchange column in buffer containing Ni(2+) affords apo-myoglobin without exposure to acidic pH or organic solvents as usually required. Bovine liver catalase, in which the heme groups are remote from the surface of the protein, and horseradish peroxidase, which has four disulfide bonds and just three histidyl residues, exhibit a much smaller spectroscopic response. We propose that formation of carbamino groups by reaction of bicarbonate with protein amino groups promotes both protein solubility and the interaction of the protein with metal ions, thereby avoiding precipitation while destabilizing the interaction of heme with the protein. From these observations, bicarbonate buffers may be of value in the study of nonmembrane proteins of limited solubility.
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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".