A Bright and Ionizable Cytosine Mimic for <i>i</i>-Motif Structures
Bibliographic record
Abstract
A new fluorescent cytosine analog “ ts C” containing a trans -stilbene moiety was synthesized and incorporated into hemiprotonated base pairs that comprise i -motif structures. Unlike previously reported fluorescent base analogs, ts C mimics the acid–base properties of cytosine (p K a ≈ 4.3) while exhibiting bright (ε × Φ ≈ 1000 cm –1 M –1 ) and red-shifted fluorescence (λ em = 440 → 490 nm) upon its protonation in the water-excluded interface of ts C +:C base pairs. Ratiometric analyses of ts C emission wavelengths facilitate real-time tracking of reversible conversions between single-stranded, double-stranded, and i -motif structures derived from the human telomeric repeat sequence. Comparisons between local changes in ts C protonation with global structure changes according to circular dichroism suggest partial formation of hemiprotonated base pairs in the absence of global i -motif structures at pH = 6.0. In addition to providing a highly fluorescent and ionizable cytosine analog, these results suggest that hemiprotonated C +:C base pairs can form in partially folded single-stranded DNA in the absence of global i -motif structures.
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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) | 0.000 | 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".