Molecular Simulations On The Adhesion Of DOPA And Its Derivatives

Mussel adhesive proteins can adhere to a variety of organic and inorganic surfaces in wet environment.Its excellent underwater adhesion properties and good biocompatibility has gained extensive application in the field of biomedicine and surface functionalization.It takes high cost to acquire mussel adhesion protein by biological extraction method,the chemical synthesis of bionic adhesive has been attracted extensive attention.However,the adhesion mechanism of mussels is still unclear,which limits its application.To understand the adhesion behavior of mussels on the surface,in this work,molecular dynamics(MD)simulations are employed to study the adhesion of 3,4-dihydroxy-phenylalanine(DOPA)and its derivatives on different surfaces.Firstly,the adhesion of single DOPA on different self-assembled monolayers(SAMs)was investigated by performing MD simulations.The adhesion free energy of DOPA on different SAMs was calculated by umbrella sampling.The results show that DOPA is more easily adhered to the negatively charged surface,the adhesion free energies are higher on charged surfaces than these of neutral surfaces.Further analysis reveals different interaction mechanisms between DOPA and different SAMs.It binds on the hydrophobic surface through benzene ring,while on the hydrophilic surface through hydroxyl.DOPA interacts with the negatively and positively charged surfaces by amino and carboxyl groups,respectively.Secondly,the adhesion of catechol and its derivatives on graphene and hydroxyl graphene was studied by MD simulations.The effects of substituted groups,the number and position of hydroxyl groups,the number of layers of graphene and number of molecules on adhesion are discussed.Simulation results indicate that both electron-donating and electron-withdrawing on the benzene ring could enhance the adhesion to graphene;the hydroxyl groups have a strongly effect for aromatic compound adhesion on graphene.Further analysis shows that adhesion free energy increased with the increase of the number of hydroxyl groups.Adhesion effect from the hydroxyl positions is weaker than that of number of hydroxyl groups.With the surface number of hydroxyl groups increasing,?-? interactions between the aromatic and graphene surface decrease.Finally,the adhesion of catechol-cation on silica surfaces was investigated by MD simulations.The effects of surface ionization degree,ionic strength and cationic amino acids on adhesion are discussed.Simulation results show that adhesion of catechol-cation onto the ionized silica surface is dominated by electrostatic interactions.At different pH,the rank of the adhesions of three catechol-cations on silica is different.Further analysis shows that the amino acid terminus has a large influence on the adhesion process,especially histidine adhesion on negatively charged surfaces.In addition,both the bulkier structure and delocalized charge of arginine decreased the cation's electrostatic interaction with the charged silica.