Research School of Biology, Australian National University, Canberra, Australia.
Biophys J. 2010 Sep 22;99(6):1734-42. doi: 10.1016/j.bpj.2010.06.034.
Synthetic channels, such as nanotubes, offer the possibility of ion-selective nanoscale pores which can broadly mimic the functions of various biological ion channels, and may one day be used as antimicrobial agents, or for treatment of cystic fibrosis. We have designed a carbon nanotube that is selectively permeable to anions. The virtual nanotubes are constructed from a hexagonal array of carbon atoms (graphene) rolled up to form a tubular structure, with an effective radius of 4.53 Å and length of 34 Å. The pore ends are terminated with polar carbonyl groups. The nanotube thus formed is embedded in a lipid bilayer and a reservoir containing ionic solutions is added at each end of the pore. The conductance properties of these synthetic channels are then examined with molecular and stochastic dynamics simulations. Profiles of the potential of mean force at 0 mM reveal that a cation moving across the pore encounters an insurmountable free energy barrier of ∼25 kT in height. In contrast, for anions, there are two energy wells of ∼12 kT near each end of the tube, separated by a central free energy barrier of 4 kT. The conductance of the pore, with symmetrical 500 mM solutions in the reservoirs, is 72 pS at 100 mV. The current saturates with an increasing ionic concentration, obeying a Michaelis-Menten relationship. The pore is normally occupied by two ions, and the rate-limiting step in conduction is the time taken for the resident ion near the exit gate to move out of the energy well.
合成通道，如纳米管，提供了离子选择性纳米孔的可能性，这些纳米孔可以广泛模拟各种生物离子通道的功能，并且有朝一日可能被用作抗菌剂，或用于治疗囊性纤维化。我们设计了一种对阴离子具有选择性渗透性的碳纳米管。虚拟纳米管由碳原子（石墨烯）的六边形阵列构建而成，卷曲成管状结构，有效半径为 4.53 Å，长度为 34 Å。孔的末端用极性羰基基团终止。由此形成的纳米管嵌入在脂质双层中，在孔的每一端添加含有离子溶液的储层。然后使用分子和随机动力学模拟检查这些合成通道的传导特性。在 0 mM 时平均力势的轮廓表明，穿过孔的阳离子遇到不可逾越的自由能势垒，高度约为 25 kT。相比之下，对于阴离子，在管的每一端附近有两个约 12 kT 的能量阱，由中间自由能势垒 4 kT 隔开。在储层中具有对称的 500 mM 溶液的情况下，孔的电导率为 72 pS，在 100 mV 时。电流随离子浓度的增加而饱和，遵循米氏-门登关系。孔通常被两个离子占据，传导的限速步骤是靠近出口门的驻留离子从能量阱中移出所需的时间。
