Abstract EANA2025-88

The origin of life likely involved short polymers of amino acids that emerged in prebiotic environments through non-enzymatic mechanisms. These abiotic peptides may still be present in organic-rich extraterrestrial samples, and their detection could offer clues about the chemical pathways that preceded biology. However, interpreting their presence requires distinguishing between sequences plausibly formed prebiotically and those likely shaped by biological evolution.

Here we present an immunoanalytical strategy for detecting and evaluating short L/D-peptide motifs in planetary analogue samples using antibodies raised against target oligomers of glycine, aspartic acid, and proline. These three amino acids were selected based on their abundance in carbonaceous meteorites and their functional relevance: glycine (G), the most abundant amino acid in meteorites, plays central roles in structural motifs; aspartic acid (D) is involved in catalysis and appears in asteroids like Bennu; and proline (P), with its unique ring structure, mediates protein—protein interactions in biology and may serve as a biosignature due to its conformational specificity.

We designed synthetic peptides representing plausible prebiotic and biotic motifs, including G4, DGD, and polyproline sequences, and generated polyclonal antibodies against them. Antibody validation was performed using inhibition immunoassays with prebiotic wet—dry cycle products and peptide-spiked mineral matrices, including Martian simulants and paleosols considered analogues of carbonaceous chondrites. Glycine oligomerization was successfully achieved under wet—dry conditions (70 °C, 15 cycles) in the presence of minerals such as sphalerite, and G4 peptides were detected down to 0.011 mM. Aspartic acid peptides showed stronger mineral adsorption, but antibody detection remained possible in crude extracts. Polyproline sequences (e.g., P5), known to require homochirality and rare under abiotic conditions, were also detectable by their corresponding antibodies.

To assess the abiotic likelihood of each motif, we developed a Monte Carlo model that simulates random polymerization according to the amino acid abundances in the Murchison meteorite. The model predicted that motifs such as G4 or DGD could plausibly emerge without biological input, while homochiral polyprolines are extremely unlikely to form abiotically, highlighting their value as potential universal biosignatures.

Overall, the antibody-based approach shows strong potential for identifying short, informative peptide sequences in complex planetary materials. Immunoassays are more tolerant of high salt concentrations and metal-rich matrices than techniques such as HPLC, and, unlike GC- MS, they do not chemically alter the sample during analysis. These features make them especially suitable for in situ applications in planetary exploration. These antibodies are part of the SOLID-LDChip project legacy and can be used for detecting short and universal prebiotic peptides in extraterrestrial samples, including those from asteroids (Ryugu, Bennu), meteorites, or samples returned from Mars or Phobos.