Secondary-Structure-Dependent Cooperation and Interference Between Peptides of Different Chain Lengths in Antifreeze Activity: Insights from Molecular Dynamics Simulations

Ice recrystallization inhibition (IRI) activity of peptides is influenced by both peptide length and secondary structure; however, whether combinations of peptides with different lengths exhibit cooperative or antagonistic effects remains poorly understood. Using molecular dynamics simulations, this study investigated how secondary structure and chain-length heterogeneity jointly affect the IRI activity of peptide-pair mixtures. For systems containing only β-sheet-rich peptides, mixtures of different chain lengths consistently reduced ice content relative to the corresponding single-peptide systems, suggesting cooperative enhancement of IRI activity. In contrast, individual α-helical peptides showed strong inhibition of ice growth, but this effect was diminished after they were mixed into peptide pairs. Structural analyses suggested that the improved performance of β-sheet mixtures was associated less with the simple preservation of native β-sheet structure than with mixing-induced changes in peptide–peptide coupling and surface exposure. By contrast, helix-containing mixtures retained more of their original local structure in some cases, but this structural retention was not accompanied by improved ice-growth suppression after mixing. Together, these findings suggest that peptide length effects on IRI are not universally synergistic but depend strongly on secondary-structure compatibility.