Elucidating the role of catechol-lysine synergy in DOPA rich mussel adhesive protein extracted from Perna viridis with pH dependent adhesion mechanism

Mussel adhesive protein (MAP) favours a strong and stable adhesion over underwater surfaces by the synergistic interactions among catechol possessing 3,4- dihydroxyphenylalanine (DOPA) with cationic lysine residues. This research focused on the elucidation of the synergistic effect between catechol and lysine at the molecular level from the DOPA-rich mussel adhesive protein extracted from the green mussel (Perna viridis). This catechol activity particularly emphasizes its pH-dependent adhesion mechanism. The extracted protein from green mussels was purified and quantified for the total protein and DOPA abundance using Lowry’s and Arnow’s assays. The existence of complete catechol functionalities and lysine-associated protein environments was evaluated by UV–visible spectroscopy, Raman spectroscopy, circular dichroism, and 1H-NMR. The availability of adhesion residues in the extracted protein was confirmed by amino acid profiling and HPLC analysis. Circular dichroism spectroscopy established a disordered secondary structure characterized by random coil and β-turn content, enabling interfacial adaptability. As protein adhesive property depends on pH, the lap shear test evaluation revealed an enhanced adhesive property of MAP at alkaline conditions, which meets the formation of a stronger bond between DOPA catechol and lysine residue at alkaline conditions. Overall, the present study provides the molecular basis of MAP adhesion chemistry and establishes a structure-function framework for bioinspired adhesion.