(302a) Protein Behaviors on Hydroxyapatite Surfaces(Invited Talk)

The physicochemical interactions between hydroxyapatite (HAP) surface and biomolecules are crucial in medical applications. The orientation and adsorption mechanism of the 10th and 7-10th type III modules of fibronectin (FN-III10, FN-III7-10) on HAP surfaces were investigated by a combination of parallel tempering Monte Carlo (PTMC) and molecular dynamics (MD) methods. The PTMC results show positively charged surface is beneficial for FN-III10 and FN-III7-10 adsorption with RGD accessible in solution, i.e., FN-III10 adsorbs with “side-on” orientation and FN-III7-10 adsorbs with “lying” orientation. The predictions are supported by related experiments. During the adsorption studied by MD, FN-III10 adsorbs on HAP surface first driven by Coulombic interactions at pre-adsorption stage, then by VDW interactions at post-adsorption stage. Under weak adsorption driven by VDW interactions, FN-III10 adsorbs above the water layer. The conformational changes of adsorbed FN-III10 mainly take place at its coil/loop parts. FN-III7-10 experiences two stages from weak adsorption to strong adsorption when Coulombic interactions become the dominant driving force. The transition is determined by the anchoring of the basic residue Arg1421 in the Ca²⁺ vacancy. The module III10 of the flexible chain-like FN-III7-10 exhibits the largest conformational change and contributes to the adsorption most. The anchoring of the guanidine group suggests that vacancies on biomaterials get the capacity to trap specific residues.