서강대학교

초록/요약

Aquaporin is a membrane protein existing in our body which works as a water channel. Multiple studies show that aquaporin has high water permeability and blocks positive or negative ions from passing through. The carbon nanotube have been recently studied as biomimetic channel for water transport, and studies show carbon nanotube also shows fast water transport characteristics. These two discovery lead to using carbon nanotube to simulate aquaporin protein. We studied the water transport characteristics of hourglass shaped nanopore with varying number and sign of charges placed at the surface of the pore using molecular dynamics simulation. The study shows that increasing the charge numbers, and negative charge compared to positive charge results in lower water flux. This result comes from interaction between water and charge, which causes higher total interaction energy for negative charge compared to positive charge. And when charge number increases, interaction increases, resulting in higher interaction energy, which frequently disrupts water movement. So negative charge compared to positive, and higher number of charge leads to higher barrier of energy for water to move. This increase of interaction can be seen in density distribution of water molecules, where negative and larger number of charges leads to discrete motion of water instead of collective motion. Also, density distribution shows energy barrier, which matches our flux result. From the diffusion coefficient we found that more interaction leads to harder movement of water molecules, and exit area of the pore shows more movement than any other area of the pore. We calculated the number of hydrogen bonds and found out that more number of bonds were present as flux lowered, since more water was present when flux lowered. This is not a matching result if hydrogen bond strength is same for all cases. So from other results, we assume that higher interaction is causing more water molecules to be inside the pore, which increases the number of hydrogen bonds but since the movement is frequently disrupted the strength of hydrogen bonds is decreasing as number increases and for negative charge compared to positive. We hope this research will provide a reference for uncovering parameters of water transport of aquaporin inspired nanopores.