Sequence-dependent molecular asymmetry and architecture define electric potential profiles of biomolecular condensates

Biomolecular condensates, which regulate diverse cellular processes, exhibit distinct electric potential profiles. This potential gradient between the dilute and the dense phases serves as the underlying driving force mediating the unique microenvironment and electrochemical activity of condensates. However, the molecular principles encoding the electric potential profiles of condensates remain unclear. In this study, we show that molecular asymmetry is a unifying origin of electric polarization in condensates. Asymmetric protein-cation and protein-anion affinities alone generate an interfacial electric double layer and a finite potential even in condensates formed by charge-free proteins. The sign of potential gradient follows the direction of the affinity bias, and the magnitude collapses onto a single linear function of dense-phase protein volume fraction across changes in chain length, interaction strength and salt concentration. Further, chain termini preferentially occupy the condensate interface, so charges positioned asymmetrically with respect to the termini create spatial charge separation even in neutral polyampholytes. These interaction-encoded and sequence architecture-encoded asymmetries can reinforce, screen or reverse one another, allowing the magnitude and polarity of the interphase potential to be tuned through sequence design or solvent environments.