Low concentration of guanidine hydrochloride induces the formation of an aggregation-prone state in α-urease
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Bibliographic record
Abstract
Canavalia ensiformis (jack bean) alpha-urease is a hexameric protein characterized by a complex denaturation mechanism. In previous papers, we have shown that a hydrophobic 8-anilino-1-naphthalenesulfonic acid (ANSA) binding conformer could be populated in a moderate concentration of denaturant. This state was obtained under conditions that had no detectable impact on its tertiary structure, as indicated by fluorescence measurements. In the present study, we further characterized this ANSA-binding state in an attempt to understand urease behavior. Evidence presented here shows that the presence of ANSA was not required for the generation of the conformer and that its affinity for ANSA came from an increase in hydrophobicity leading to aggregation. Circular dichroism investigation of urease revealed that it had periodical secondary structure content similar to Klebsiella aerogenes urease (secondary structures calculated on the basis of crystallographic data). The impact of 0.9 M guanidine hydrochloride (GuHCl) on soluble urease secondary structures was minimal but is compatible with a slight increase in beta-sheet structures. Such modification may indicates that aggregation involves amyloid-like fibril formation. Electron microscopy analysis of urease in the absence of GuHCl revealed the presence of urease hexamers (round shape 13 nm in diameter). These particles disappeared in the presence of moderate denaturant concentration owing to the formation of aggregates and fibril-like structures. The fibrils obtained in 1.5 M GuHCl had an average diameter of 6.5 nm, suggesting that urease hexamers dissociated into smaller oligomeric forms when forming such fibrils.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 it