Bedrov Dmitry, Smith Grant D, Davande Hemali, Li Liwei
Department of Materials Science & Engineering, 122 South Central Campus Drive Room 304, University of Utah, Salt Lake City, Utah 84112, USA.
J Phys Chem B. 2008 Feb 21;112(7):2078-84. doi: 10.1021/jp075149c. Epub 2008 Jan 30.
To investigate the implications of the unique properties of fullerenes on their interaction with and passive transport into lipid membranes, atomistic molecular dynamics simulations of a C60 fullerene in a fully hydrated di-myristoyl-phoshatidylcholine lipid membrane have been carried out. In these simulations the free energy and the diffusivity of the fullerene were obtained as a function of its position within the membrane. These properties were utilized to calculate the permeability of fullerenes through the lipid membrane. Simulations reveal that the free energy decreases as the fullerene passes from the aqueous phase, through the head group layer and into the hydrophobic core of the membrane. This decrease in free energy is not due to hydrophobic interactions but rather to stronger van der Waals (dispersion) interactions between the fullerene and the membrane compared to those between the fullerene and (bulk) water. It was found that there is no free energy barrier for transport of a fullerene from the aqueous phase into the lipid core of the membrane. In combination with strong partitioning of the fullerenes into the lipidic core of the membrane, this "barrierless" penetration results in an astonishingly large permeability of fullerenes through the lipid membrane, greater than observed for any other known penetrant. When the strength of the dispersion interactions between the fullerene and its surroundings is reduced in the simulations, thereby emulating a nanometer sized hydrophobic particle, a large free energy barrier for penetration of the head group layer emerges, indicating that the large permeability of fullerenes through lipid membranes is a result of their unique interaction with their surrounding medium.
为了研究富勒烯的独特性质对其与脂质膜相互作用及被动转运的影响，我们对完全水合的二肉豆蔻酰磷脂酰胆碱脂质膜中的C60富勒烯进行了原子分子动力学模拟。在这些模拟中，富勒烯的自由能和扩散系数是其在膜内位置的函数。利用这些性质计算了富勒烯通过脂质膜的渗透率。模拟结果表明，当富勒烯从水相穿过头基团层进入膜的疏水核心时，自由能降低。自由能的降低并非由于疏水相互作用，而是由于富勒烯与膜之间的范德华（色散）相互作用比富勒烯与（大量）水之间的相互作用更强。研究发现，富勒烯从水相进入膜的脂质核心的转运不存在自由能障碍。结合富勒烯在膜脂质核心中的强烈分配，这种“无屏障”渗透导致富勒烯通过脂质膜的渗透率惊人地高，高于任何其他已知渗透剂。在模拟中，当富勒烯与其周围环境之间的色散相互作用强度降低，从而模拟纳米尺寸的疏水颗粒时，出现了穿过头基团层的大自由能障碍，这表明富勒烯通过脂质膜的高渗透率是其与周围介质独特相互作用的结果。
