Molecular Dynamics Simulation Of Hen Egg Lysozyme Adsorption On Carbon Nanotubes

Hen egg white lysozyme (HEWL) is a water-soluble and stable protease,and the experimental results show that it has good dispersion.of carbonnanotubes (CNTs). In our work, we have simulated the HEWL adsorptionbehavior on carbon nanotubes surface by using molecular dynamics method.We selected six adsorption orientation and took50ns computer simulation foreach orientation in300K temperature conditions. Adsorption took place in allsix orientations, and the amino acid residues faced to the surfaces of carbonnanotubes will change to a more flexible structure during the absorption, inorder to increase the coverage area on carbon nanotubes surface. In the50nssimulation, the interaction energy between HEWL and carbon nanotubesincreases with the extension of time, and the increasing is stepwise. It suggeststhat HEWL have to over certain energy barriers before finally achievedadsorption balance. And it’s a long time from initial adsorption to reachequilibrium adsorption state.In order to study whether the adsorption would affect HEWL’s catalyticactivity, we added the substrate-MGM. The simulation results show that thefixation of the ends of the substrate is important to catalytic action, and residues of the active site has a stronger interaction with carbon nanotubesthan substrate. So in the immobilized process we should avoid the active sitebeing too close to the carbon nanotubes surface. If the distance between theactive site residues and the surface is beyond the adsorption range, theadsorption state HEWL has a more stable interaction with substrate thanisolated state.Some experiment results suggest that the dispersion of carbon nanotubesby HEWL is related to the temperature increase in the process of ultrasonic.Sowe carried out50ns simulation in50℃,70℃,80℃and90℃conditions.Simulation results show that the high temperature can shorten the equilibriumadsorption time, and it leads to a portion the internal secondary structure inHEWL unfolded. In the unfolding process, the " Hydrophobic box " oflysozyme molecules quickly move to the carbon nanotube surface, to enhancethe adsorption between them.