Lessons from an aged, dried crystal of T<sub>6</sub>human insulin
Bibliographic record
Abstract
The structure of the T(6) hexameric form of human insulin has been determined at both room temperature and 100 K from a single air-dried crystal. At 100 K, the space group is R3 and the asymmetric unit consists of a dimer, as has been observed previously in hydrated structures. At room temperature, the space group is P1 and the unit cell contains a quasi-threefold-symmetric hexamer. In the absence of stabilizing water interactions, the N-termini of all six A chains in the room-temperature structure appear to have undergone partial unfolding, but the N-termini of these chains are well ordered in the 100 K structure. Other differences between the room-temperature and 100 K structures involve the coordination around the zinc ions. At 100 K, both zinc ions clearly exhibit dual coordination: zinc is octahedrally coordinated in one half of the zinc sites but tetrahedrally coordinated in the other half; at room temperature, the electron densities suggest tetrahedral coordination but the bond distances to the fourth ligands are longer than expected. Contrary to what has been observed to date in all other T(6) insulin structures, there are no contacts between pairs of GluB13 residues, either at room temperature or at 100 K, that would suggest the presence of a hydrogen bond. At room temperature, three of the six independent GluB13 side chains are disordered; at 100 K, both independent side chains are disordered. The disorder in the GluB13 side chains and the lack of contacts between carboxylate groups suggests that as a result of disruption of the hydration structure in the central core of the hexamer, all six B13 carboxylates bear a negative charge. This in turn suggests that in the hydrated structures the well ordered water structure in the central core is involved in stabilizing the B13 side-chain conformations and modulating charge repulsions among the six B13 glutamates if they are not protonated, or that, as is considered more likely, the water structure plays an important role in modulating the pK(a) values of the B13 glutamates, resulting in protonation and hydrogen-bond formation.
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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 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.003 |
| Insufficient payload (model declined to judge) | 0.003 | 0.001 |
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".