Catechol-Vanadium Binding Enhances Cross-Linking and Mechanics of a Mussel Byssus Coating Protein

Abstract

Inspired largely by chemistry discovered in the byssus fibers of marine mussels, 3,4-dihydroxyphenylalanine (DOPA)-metal coordination has emerged as an effective cross-linking strategy for producing a range of high-performance supramolecular polymers and adhesives with desirable mechanical properties. Recent findings have revealed that mussels often use vanadium in these complexes to enhance the cohesion, rather than solely iron as conventionally believed. Here, we utilized a recombinant DOPA-functionalized mussel protein (rMfp-1-DOPA) to investigate the implications of vanadium-based cross-linking using both nanomechanical and spectroscopic methods. We discovered that DOPA-V cross-linking can strengthen the cohesion of the protein network by nearly twofold compared with DOPA-Fe. Spectroscopic analysis with UV-vis, Raman, and EPR indicated that vanadium is more effective at forming tris-DOPA-metal complexes under the pH ranges relevant to byssus formation and function, especially when starting with the V-III form. Furthermore, when compared with a pure catechol control, rMfp-1-DOPA can form DOPA-V complexes at very low pH values relevant to the byssus formation process, suggesting that the protein sequence may be adapted for V binding. These findings provide evidence that DOPA-V coordination is advantageous for both the formation and function of the byssus, which is highly relevant for continued efforts to develop mussel-inspired metallopolymers.