Microscopic origins of the viscosity of RNA-peptides condensates

The study of rheological properties in biomolecular condensates provides valuable insights into their dynamic behavior and viscoelastic characteristics, shedding light on the physical principles governing their formation and function in cellular processes. Rheological properties of biomolecular condensates however remain challenging to describe from a microscopic perspective. Recent experiments have shown Arrhenius law of viscosity in peptide-ssDNA condensates which indicates the existence of a well-defined flow activation energy. In this study, we investigate the microscopic origin of flow activation energy in bio-condensates by using coarse-grained simulations of peptide and nucleic acid mixtures. Our aim is to uncover the intricate relationship between association-dissociation process and rheological properties. We find that viscosity in these condensates depends on a complex interplay among intermolecular interactions, chain properties and temperature. Under specific conditions, our simulations demonstrate a strong correlation between the binding lifetime of stickers and the viscosity of the condensates. Furthermore, we explore the impact of other factors on activation energy, such as the monomer sequence of peptides and chain length. Our results offer insights into the multi-scale rheology of biomolecular condensates, providing a deeper understanding on the micro-level functional design of peptides.