Purification, crystallization and preliminary X-ray diffraction studies of xanthine dehydrogenase and xanthine oxidase isolated from bovine milk
Bibliographic record
Abstract
Xanthine dehydrogenase catalyzes the oxidation of hypoxanthine to xanthine and the further oxidation of xanthine to uric acid. The enzyme is the target of the anti-gout drug allopurinol and its involvement in postischemic reperfusion injury is presently being defined. Each subunit of the homodimeric 290 kDa enzyme contains four cofactors: one Mo-pterin, two [2Fe-2S] clusters and one FAD. Both the dehydrogenase (XDH) and the proteolytically modified oxidase form (XO) of the enzyme from bovine milk have been crystallized. XO crystals belong to space group C222(1), with unit-cell parameters a = 116.3, b = 164.4, c = 153.2 A at room temperature and a = 117.8, b = 165.4, c = 154.5 A when flash-frozen. They allow data collection to 3.3 and 2.5 A, respectively. In addition, a data set was collected from frozen XDH crystals and processed to 2.1 A. These crystals belong to space group C2, with unit-cell parameters a = 169.9, b = 124.8, c = 148.6 A, beta = 90.9 degrees. The unit-cell volumes and Matthews parameters are similar for the two crystal forms. There is one monomer per asymmetric unit in the XO crystals and a complete native dimer per asymmetric unit in the XDH crystals.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 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".