Molecular dynamics of reversible iron-catechol complexes as a toughening mechanism for mussel foot protein assemblies

<h2>Summary</h2> Metal-catechol coordination is a principal design feature of mussel foot proteins (mfps) that facilitate tough underwater adhesion. Single-molecule models of metal-protein complexes cannot predict the outstanding cohesive properties of mussel-inspired adhesive interfaces because they lack the resolution at the scale of intermolecular networks. Here, we elucidate these dynamics by establishing a fully atomistic framework for modeling bulk mfp-inspired materials to observe the reversible dynamics of Fe³⁺-mediated catechol crosslinks. We first developed parameters for covalent and ionic crosslinks formed by catechol groups and validated them against quantum-mechanical studies. We then demonstrated how rupture and reformation of Fe³⁺-catechol crosslinks and DOPA deprotonation enhance the mechanical properties of the material. Correlating coordination dynamics with peaks in the sawtooth stress-strain curves ascertains the molecular origins of toughness in metal-coordinated biopolymers. These findings provide a predictive platform for designing sequence-defined mfp-inspired materials that are critically needed for wet bonding and surgical adhesives.