Structural and electronic properties of barbituric acid and melamine-containing ribonucleosides as plausible components of prebiotic RNA: implications for prebiotic self-assembly
Why this work is in the frame
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Bibliographic record
Abstract
The RNA world hypothesis assumes that RNA was the first informational polymer that originated from prebiotic chemical soup. However, since the reaction of d-ribose with canonical nucleobases (A, C, G and U) fails to yield ribonucleosides (rNs) in substantial amounts, the spontaneous origin of rNs and the subsequent synthesis of RNA remains an unsolved mystery. To this end, it has been suggested that RNA may have evolved from primitive genetic material (preRNA) composed of simpler prebiotic heterocycles that spontaneously form glycosidic bonds with ribose. As an effort toward evaluating this hypothesis, the present study uses density functional theory (DFT) to assess the suitability of barbituric acid (BA) and melamine (MM) to act as prebiotic nucleobases, both of which have recently been shown to spontaneously form a glycosidic bond with ribose and organize into supramolecular assemblies in solution. The significant strength of hydrogen bonds involving BA and MM indicates that such interactions may have played a crucial role in their preferential selection over competing heterocycles that interact solely through stacking interactions from the primordial soup during the early phase of evolution. However, the greater stability of stacked dimers involving BA or MM and the canonical nucleobases compared to those consisting solely of BA and/or MM points towards the possible evolution of intermediate informational polymers consisting of prebiotic and canonical nucleobases, which could have eventually evolved into RNA. Analysis of the associated rNs reveals an anti conformational preference for the biologically-relevant β-anomer of both BA and MM rNs, which will allow complementary WC-like hydrogen bonding that can stabilize preRNA polymers. Large calculated deglycosylation barriers suggest BA rNs containing C-C glycosidic bonds are relevant in challenging prebiotic environments such as volcanic geotherms, while lower barriers indicate the MM rNs containing C-N-C glycosidic linkages may have been more likely synthesized from simple precursors such as urea-ice in icy (polar) regions. Together, our quantum chemical data clarifies the physicochemical interactions and stability of potential prebiotically-relevant constituents of BA and MM polymeric assemblies, and complements information from previous experimental studies to bolster the candidature of these heterocycles as prebiotic nucleobases.
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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