Protonation and Anion Binding Control the Kinetics of Iron Release from Human Transferrin
Bibliographic record
Abstract
Iron release in vitro from human serum diferric transferrin (hFe(2)Tf) in acidic media (4.2 ≤ pH ≤ 5.4) in the presence of nonsynergistic anions occurs in at least five kinetic steps. Step 1 (most rapid) involves proton assisted release of carbonate from the protein. In subsequent steps, iron release from both the N- and C-terminal lobes is controlled by slow proton transfers and anion binding. In step 2, the N-terminal lobe takes up one proton with kinetic linkage to the binding of one anion. In step 3, iron release from the anion-linked N-terminal lobe is controlled by slow uptake of two protons with rate-constant, k(2N), of 2.6(6) × 10(7), 6.1(6) × 10(7), and 9(1) × 10(7) M(-2) s(-1) in the presence of Cl(-), NO(3)(-), and SO(4)(2-), respectively. In step 4, the C-terminal lobe takes up one proton with kinetic linkage to the binding of one anion. In step 5, iron release from the anion-linked C-terminal lobe is controlled by slow uptake of two protons with rate-constant, k(2C), of 8.4(2) × 10(4), 4.4(6) × 10(5), and 8.1(2) × 10(5) M(-2) s(-1) in the presence of Cl(-), NO(3)(-), and SO(4)(2-), respectively.
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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 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".