The study presents a minimalistic model for liquid-liquid phase separation (LLPS) using fluorenylmethoxycarbonyl (Fmoc)-protected single amino acids (Fmoc-AAs). The authors systematically investigate how different Fmoc-AAs undergo LLPS based on hydrophobic interactions, pH, and ionic strength. Their findings highlight residue-dependent variations in critical concentrations and phase behavior, demonstrating that hydrophobic interactions predominantly drive phase separation. Furthermore, they explore the transition from liquid condensates to solid aggregates, revealing that this transformation may be governed by mechanisms distinct from LLPS. These insights contribute to the understanding of biomolecular condensation and its implications in cellular organization and protein aggregation diseases.

The researchers also analyze how environmental factors such as salt concentration, pH, and temperature affect the stability and behavior of Fmoc-AA condensates. Notably, the study shows that mixing different Fmoc-AAs, including enantiomers, significantly enhances the stability of condensates by disrupting molecular stacking, thereby preventing rapid aggregation. This suggests that phase separation and subsequent fibrillization are controlled by different molecular interactions. Additionally, molecular dynamics simulations corroborate these experimental observations, further elucidating the role of hydrophobicity in the condensation process.

Beyond fundamental insights, the study explores potential applications of Fmoc-AA condensates in mimicking cellular environments. The authors demonstrate that these condensates can selectively accommodate biomolecules and facilitate chemical reactions, highlighting their potential as artificial cells or catalytic microreactors. The enhanced reaction rates within the condensates suggest that they provide a unique microenvironment for biochemical transformations. Overall, this research advances our understanding of phase separation and protein aggregation, offering a versatile model system with applications in synthetic biology and material science.

- Author (Pusan National University): Jeong-Mo Choi (Department of Chemistry)

- Title of original paper: A Single Amino Acid Model for Hydrophobically Driven Liquid-Liquid Phase Separation

- Journal: Biomacromolecules

- Web Link: https://doi.org/10.1021/acs.biomac.4c01410