Protonation of histidine 55 affects the oxygen access to heme in the alpha chain of the hemoglobin from the Antarctic fish <i>Trematomus bernacchii</i>
Bibliographic record
Abstract
The Root effect describes the drastic drop of oxygen affinity and loss of cooperativity at acidic pH expressed in the hemoglobins (Hb) of certain fish. The comparison between the deoxy structures of the Root effect Hb from the Antarctic fish Trematomus bernacchii (HbTb) at different pHs (pH = 6.2 and pH = 8.4) shows that the most significant differences are localized at the CDα region, where a salt bridge between Asp48 and His55 breaks during the low-to-high pH transition. In order to shed light on the relationship between pH, CDα loop structure and dynamics, and oxygen access to the active site in the alpha chain of HbTb, different computer simulation techniques were performed. Our results highlight the importance of the protonation of His55 in regulating oxygen access, underscoring its pivotal role in the structural and functional properties of HbTb. These data provide further support to the hypothesis that this residue might contribute to the release of Root protons in HbTb and underline the fact that an efficient transport of molecular oxygen in Hbs relies on a subtle balance of tertiary structure and protein conformational flexibility.
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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".