Getting specificity from simplicity in putative proteins from the prebiotic Earth
Bibliographic record
Abstract
Can unique protein structures arise from a limited set of amino acids present on the prebiotic earth? To address this question, we have determined the stability and structure of KIA7, a 20-residue polypeptide containing chiefly Lys, Ile, and Ala. NMR methods reveal that KIA7 tetramerizes and folds on the millisecond time scale to adopt a four-helix X-bundle structure with a tightly and specifically packed core. Denaturation studies and hydrogen exchange measurements of KIA7 and several variants demonstrate that ridges-into-grooves packing of Ala and Ile side chains and the packing of a C-terminal aromatic group into the hydrophobic core are sufficient to give rise to a rather stable, well folded protein structure, with no favorable electrostatic interactions or tertiary or quaternary hydrogen bonds. Both modern proteins and RNAs can adopt specific structures, but RNAs do so with a limited "alphabet" of residues and types of stabilizing interactions. The results reported here show that specific, well folded protein structures can also arise from a highly reduced set of stabilizing interactions and amino acids that are thought to have been present on the prebiotic earth.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| 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".