Thesis Defense – Dean Jarois

Liquid-liquid phase separation (LLPS) is responsible for the formation of membraneless organelles in cells and is often regarded as a plausible mechanism for prebiotic compartmentalization. While LLPS has been widely studied with homochiral peptides and proteins, the effect of peptide heterochirality of phase separation is not yet understood. Here we investigate how peptide length, chiral composition, and sequence can affect phase separation propensity with hexametaphosphate. Phase behavior was determined with microscopy and optical density measurements. We found that heterochiral substitutions on peptide 13-mers cause differences in LLPS propensity determined by the spatial arrangement of D-amino acid substitutions. We propose more experiments that can determine whether residue identity, spacing, or backbone disruptions govern this effect.