Functional Design and Biophysical Characterization of Analyte-Responsive Polymers.

As a proof-of-concept for analyte-responsive polymers (ARPs) for biosensing, this study investigates how ligand binding changes the temperature-dependent dynamics and self-assembly of an elastin-like polymer (ELP) fused with a peptide recognition element for the small globular protein domain SH3. Using isothermal titration calorimetry, we characterized the apparent binding thermodynamics when one binding partner is fused with an ELP. Circular dichroism, dynamic light scattering, and temperature-dependent UV-vis spectroscopy were used to examine how ligand binding influences ARP conformational dynamics and phase behavior. SH3 binding was associated with an increase in transition temperature that reproduced in a complex medium and was consistent with predictions from a published model for ELP fusions. Addition of SH3 destabilized ARP assemblies, demonstrating that an ARP response can be specifically triggered by ligand binding. This work advances our understanding of how ligand binding and phase behavior are interdependent in systems involving intrinsically disordered proteins and their assemblies.