Purification, crystallization and preliminary X-ray analysis of a μ-like calpain
Bibliographic record
Abstract
The X-ray structure of m-calpain in the absence of Ca(2+) has been described, but it has not been possible to obtain sufficient mu-calpain for structure determination. Comparison of the two structures is of interest in attempting to understand their different Ca(2+) requirements. Here, the crystallization in the absence of Ca(2+) of an inactive mutant hybrid calpain (MW approximately 100 kDa), which contains 85% of the rat mu-calpain sequence and is well expressed in Escherichia coli, is described. The properties of this calpain in its active form and particularly its Ca(2+) requirement are close to those expected for wild-type mu-calpain. Clusters of plate-shaped crystals were obtained by vapour diffusion with polyethylene glycol (M(r) approximately 6000) as precipitating agent in the presence of detergent. The crystals diffract to a resolution of 2.7 A at a synchrotron source. The space group is P2(1), with unit-cell parameters a = 72.7, b = 184.6, c = 86.3 A, beta = 100.7 degrees. There are two molecules in the asymmetric unit, corresponding to a solvent content of 57.1%.
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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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".