M-DNA: pH Stability, Nuclease Resistance and Signal Transmission
Bibliographic record
Abstract
Abstract In the presence of divalent metal ions (Zn(2)+, Co(2)+, and Ni(2)+) and at pHs above 8, duplex DNA forms a complex called M-DNA. M-DNA can be converted back to B-DNA by addition of EDTA or lowering the pH. The stability of M-DNA depends on the metal ion and/or the sequence of DNA. For calf thymus DNA the order of stability with decreasing pH is: Ni(2+)> Co(2+)>Zn(2++). The interconversion with B-DNA shows hysteresis; once formed Ni-M- DNA remains stable for more than one hour at pH 7, but conversion of B-DNA to M-DNA is slow at pHs below 8. Among synthetic sequences, poly[d(AT)] does not form M-DNA whereas the phosphorothioate analogues form only at pH 9.0. In contrast, the Ni-M-DNA form of poly[d(GC)] is stable even at pH 6.5. Ni-M-DNA is resistant to cleavage by DNase I whereas B-DNA is digested rapidly under identical conditions. The Co(2)+ and Ni(2+) forms of M-DNA were paramagnetic with increased mass susceptibilities (χ) compared to other metal complexes. Signal transmission in M-DNA was tested by constructing duplexes of 54 base pairs with fluorescein (donor) at one end and rhodamine (acceptor) at the other. Quenching of fluorescein fluorescence was observed for the Zn(2+) form of M-DNA only when the DNA was labeled with both donor and acceptor. Therefore, the pathway of quenching maybe via electron transfer. Taken together, these results suggest that M-DNA is a distinct conformation with tightly bound metal ions, and certain forms may be stable under physiological conditions. Furthermore, M-DNA may be used as a molecular wire for signal transmission over long distances.
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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 | 0.001 |
| 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) | 0.001 | 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 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".