To mix or to de-mix?: Cation-π suppresses heterogeneity in local structure and dynamics of heterotypic Condensates

Abstract

Heterotypic biomolecular condensates can exhibit pronounced spatial and dynamic heterogeneity because chemically distinct components compete between self- and cross-association. Here, we use coarse-grained simulations to investigate how cation-{pi} interactions modulate this competition in condensates formed by peptides with systematic variation of hydrophobicity-to-charge ratios in binary peptide pairs. By independently tuning sequence heterogeneity, peptide composition, and cation-{pi} interaction strength, we establish how an additional short-range interaction reshapes condensate stability, internal organization, and molecular dynamics. In the absence of cation-{pi} interactions, highly heterogeneous peptide pairs form distinct core-shell architectures, with charge- and hydrophobicity-rich sequences preferentially occupying different regions of the condensate. Introducing cation-{pi} interactions progressively enhances phase stability and promotes molecular mixing, with stronger interactions substantially increasing the critical temperature and condensate density. Energetic analysis reveals that cation-{pi} interactions partially compensate for the loss of electrostatic and hydrophobic stabilization, providing an additional and tuneable source of cohesive interactions. This enhanced cross-association also suppresses spatial and dynamic heterogeneity, yielding more homogeneous peptide distributions, slower translational diffusion, and more uniform chain reconfiguration within the dense phase. Collectively, our results demonstrate that cation-{pi} interactions provide a molecular mechanism for coupling condensate stability to spatial organization and internal dynamics, enabling sequence heterogeneity and composition to be translated into distinct condensate states.