Abstract
Multivalent binding is essential to many biological processes because it builds high affinity bonds by using several weak binding interactions simultaneously. Multivalent polymers have shown promise as inhibitors of toxins and other pathogens, and they are important components in the formation of biocondensates. Explaining how structural features of these polymers change their binding and subsequent control of phase separation is critical to designing better pathogen inhibitors and also to understanding diseases associated with membraneless organelles. In this work, we will examine the binding of a multivalent polymer to a small target. This scenario could represent a polymeric inhibitor binding to a toxic protein or RNA binding to an RNA-binding protein in the case of liquid-liquid phase separation. We use simulation and theory to show that flexible random-coil polymers bind more strongly than stiff rod-like polymers and that flexible polymers nucleate condensed phases at lower energies than their rigid analogues. We hope these results will provide insight into the rational design of polymeric inhibitors and improve understanding of membraneless organelles.
Statement of Significance Multivalent polymers are essential for many biological systems, including targeting pathogens and controlling the formation of liquid-liquid phase separated biocondensates. Here, we explain how increasing polymer stiffness can reduce multivalent binding affinity to a small target such as a toxic protein and how modulating polymer stiffness can change the phase boundary for liquid-liquid phase separation. These results have implications for designing stronger pathogen inhibitors and provide insights on neurodegenerative diseases associated with abnormal biocondensate formation.