Cascade of phase transitions in a dipeptide supramolecular assembly triggered by a single fatty acid

Significant progress has been achieved with diversity of short peptide supramolecular assemblies. However, their programmable phase modulation by single stimulus remains a great challenge. Herein, we demonstrate a dipeptide supramolecular system undergoes sequentially coupled phase transitions upon hydrogen bonding association and dissociation triggered by a single fatty acid. To be specific, fatty acid at a low specific ratio mediates gel-crystal transformation of the dipeptide supramolecular assembly by rearrangement of hydrogen bonding interactions. Moreover, fatty acid at a high specific ratio induces crystal-sol transition by protonation of the dipeptide, generating strong electrostatic repulsion to cleave hydrogen bonding interactions. Remarkably, the cascade of phase transitions enables spontaneous solid-liquid separation of the dipeptide from one dispersion phase and further dissolution in another in a capture and release fashion. In contrast, it is not facilitated by individual phase transition. Our work creates competitive pathways to achieve integration of phase transitions in a simple dipeptide supramolecular system. It is useful to deeply understand the dynamic and complex biomolecular condensates in nature and with important implications for efficient collection of biomolecules.