Synthesis of nucleosidic bonds using a nucleoside hydrolase in aqueous-organic media
Bibliographic record
Abstract
The synthesis of inosine from nonactivated and nonprotected ribose and hypoxanthine was performed by enzyme-catalyzed condensation, using a nucleoside hydrolase from Crithidia fasciculata expressed in Escherichia coli with a synthetic gene. One round of directed evolution was performed in the presence of dimethylformamide, used to lower the water activity in the reaction media, leading to a double mutant (Asp54Asn, Arg137Gly). It afforded a doubling of the specificity constant for the hydrolysis of p-nitrophenol-β-d-riboside in the presence of 40% acetonitrile. In aqueous conditions, concentrations of 0.1 and 0.2 mM inosine were obtained, starting from 25 mM hypoxanthine and 2 or 3 M ribose, respectively. With 20% acetonitrile increases of 95% and 60% were observed. These conversions are very low, and the work exemplifies the difficulties encountered when trying to define conditions for hydrolase-catalyzed condensation and at the same time evolve an enzyme to perform well in these a priori unknown conditions.
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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) | 0.000 | 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) | 0.001 | 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".