Dynamic Response of Surface-Bound Peptides to a pH Perturbation Under Controlled Electrostatic Conditions

The dynamic conformations of a thin peptide film covalently-linked to the surface of a transparent electrode are characterized over the course of a perturbation to their local pH by a photoacid under a controlled electrostatic potential. The local environment at this functionalized electrified interface is probed by the ultrafast fluorescence intensity and transient anisotropy of chromophores sparsely attached to the peptide side chains. A partition of chromophores into two sub-populations is observed, one buried in the peptide layer and another that is solvent exposed, and their relative contributions to the observed fluorescence signal are affected by both pH and voltage stimuli. The photophysical properties of solvent-exposed chromophores reveal that while the average conformation of the peptide mat is dictated by the pH of the surrounding electrolyte, their fluctuations are largely determined by the local electrostatic conditions set by the electrode's surface potential.