Polypeptide-Solvent Interactions Measured by Single Molecule Force Spectroscopy

Stimulus-responsive biomolecules have attracted a large research interest because of their potential application in various areas such as drug delivery, actuators and sensing devices at the nanoscale. Using single-molecule force spectroscopy (SMFS) we studied elastin-like polypeptides (ELPs). These stimulus-responsive polypeptides undergo an inverse temperature transition, accompanied by a large conformational change, when the solvent quality is changed by increasing the temperature or by addition of salt. Understanding the relationship between peptide sequence and mechanisms of force generation can provide a route to engineer ELPs with desirable mechano-chemical properties. Here we studied the effect of solvent quality and type of guest residue on the mechanical properties of ELPs on the single-molecule level. We used a statistical approach to estimate polymer elasticity parameters from model fits to the data. With this approach we were able to resolve small changes in the Kuhn segment length distributions associated with different molecular architectures. We then show that these mechanical differences likely arise from differences in the hydrophobic hydration of sidegoups, in line with recent predictions from molecular dynamics simulations.