Environmental constraints on the origin of life based on membrane formation: the role of salinity
Bibliographic record
Abstract
Abstract The environmental conditions for the origin of life are still not well-constrained, but membrane-bound structures must have been key to the origin of life. Membranes composed of fatty acids are promising candidates due to their simplicity and plausible prevalence in prebiotic environments. To assess the stability of membranes composed of fatty acids with tail lengths ranging from 12 to 16 carbons at different temperatures and sodium chloride concentrations that may have existed on the early Earth, we conducted all-atom molecular dynamics (MD) simulations. In the absence of salt (freshwater), none of the fatty acids exhibited bilayer formation, whether below or above their chain melting temperature. However, elevating the salt concentration from 0.15 M (saline solution), 0.5 M (seawater), 1 M (seawater tide pools), 3 M (salty tide pools) and 5 M (Dead Sea) resulted in the formation of stable bilayers. The 16-carbon fatty acid required lower salt concentration, while shorter, 12-carbon chain necessitated higher salt levels. Increasing the salt concentration led to three main effects: (1) increased bilayer thickness, (2) reduced area per fatty acid and (3) elevated deuterium order parameter of the chains, resulting in more robust membranes. Our simulations indicated that the salt cations aggregated on the bilayer surfaces, effectively mitigating repulsive interactions among hydrophilic fatty acid head groups. These findings suggest that fatty acid bilayers are more likely present in ancient waters connected to saltwater reservoirs, or seawater tide pools with elevated salt concentrations.
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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) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 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".