Experimentally, the solubility of
oligoglycines in water decreases
as its length increases. Computationally, the free energy of solvation
becomes more favorable with chain length for short (n = 1–5) oligoglycines. We present results of large scale simulations
with over 600 pentaglycines at varying concentrations in explicit
solvent to consider the mechanism of aggregation. The solubility limit
of Gly5 for the force field used was calculated and compared
with experimental values. We find that intermolecular interactions
between pentaglycines are favored over interactions between glycine
and water, leading to their aggregation. However, the interaction
driving peptide associations, liquid–liquid phase separation,
are not predominantly hydrogen bonding. Instead, non-hydrogen bonding
interactions between partially charged atoms on the peptide backbone
allow the formation of dipole–dipole and charge layering correlations
that mechanistically stabilize the formation of large, stable peptide
clusters.