Molecular Dynamics Study on Lipid Wrapped Carbon Nanotube as an Artificial Membrane Channel

Abstract

Carbon nanotube (CNT) is an ideal membrane channel because of its hydrophobic inner pore and prominent transport properties like typical biological channels. These CNT porins can transport water, small ions, and DNA. CNT-membrane interaction simulation shows that CNTs having a length similar to the thickness of lipid bilayer can be inserted into membrane and sustain angle almost perpendicular to membrane. Much longer ones can also be inserted into membrane but they are buried inside hydrophobic region of membrane (1). However, recent experimental research elucidated that longer CNTs wrapped by lipids can be inserted into lipid-bilayer and maintain their angle within 15 degrees (2).In this study, we performed molecular dynamics simulation for investigating interaction between lipids wrapped CNT and lipid-bilayer. Martini coarse-grained force field was used to reduce computational cost significantly. Also, wrapping process was analyzed by using the coarse-grained carbon nanotube (CG-CNT) and the 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) in various CNT length and surface adsorption density, respectively. Furthermore, we performed insertion simulation to see how these properties affect insertion process and finally compared CG-CNT's insertion angles with experimental data. As a result, CNT insertion takes longer time in general as the density of wrapped lipid increases. Also, we realized that CNT can maintain its insertion angle almost perpendicular to lipid-bilayer at a certain critical density.Finally, its insertion mechanism is fully discussed with respect to interaction energy between the wrapped CG-CNT and lipid membrane.(1) Lelimousin, M., and M. S. P. Sansom. 2013. Small 9:3639-3646.(2) Geng, J., K. Kim, J. F. et al. 2014. Nature 514:612-+.