Expression, purification, crystallization and preliminary X-ray analysis of<i>Escherichia coli</i>5′-methylthioadenosine/<i>S</i>-adenosylhomocysteine nucleosidase
Bibliographic record
Abstract
A recombinant form of Escherichia coli 5'-methylthioadenosine/S-adenosylhomocysteine nucleosidase (E.C. 3.2.2.9) has been purified to homogeneity and crystallized using the hanging-drop vapour-diffusion technique. While several different crystallization conditions were obtained, only one set of conditions yielded crystals suitable for X-ray diffraction analysis. These crystals grow as diamond-shaped wedges, with unit-cell parameters a = 50.92, b = 133.99, c = 70.88 A, alpha = beta = gamma = 90 degrees. The crystals belong to space group P2(1)2(1)2 and diffract to a minimum d spacing of 2.3 A on a MAR345 image plate with a Rigaku RU-200 rotating-anode X-ray generator. On the basis of density calculations, two monomers are predicted per asymmetric unit (Matthews coefficient, V(M) = 2.37 A(3) Da(-1)), with a solvent content of 48%.
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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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.001 | 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".