An Exceptionally Selective DNA Cooperatively Binding Two Ca<sup>2+</sup> Ions
Why this work is in the frame
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Bibliographic record
Abstract
Abstract Ca 2+ is a highly important metal ion in biology and in the environment, and thus there is extensive work in developing sensors for Ca 2+ detection. Although many Ca 2+ ‐binding proteins are known, few nucleic acids can selectively bind Ca 2+ . DNA‐based biosensors are attractive for their high stability and excellent programmability. We report a RNA‐cleaving DNAzyme, EtNa, cooperatively binding two Ca 2+ ions but to only one Mg 2+ . Four DNAzymes with known Ca 2+ ‐dependent activity were compared, and the EtNa had the best selectivity for Ca 2+ . The EtNa is 90 times more active in Ca 2+ than in Mg 2+ . Phosphorothioate (PS) modification showed that both non‐bridging oxygen atoms at the scissile phosphate contribute equally to Ca 2+ binding. The pH–rate profile suggests two concurrent deprotonation reactions. EtNa was further engineered for Ca 2+ sensing, and found to have a detection limit of 17 μ m Ca 2+ and excellent selectivity. The detection of Ca 2+ in tap water was performed, and the result was comparable with that by ICP‐MS. This study offers new fundamental insights into Ca 2+ binding by nucleic acids and improved metal selectivity by having multiple cooperative metal binding sites.
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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 | 0.001 | 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