多巴胺在POPC磷脂双层膜中扩散和透过过程的分子动力学模拟

Molecular Dynamics Simulation of Dopamine Diffusion within and Permeation through POPC Phospholipid Bilayer Membrane

多巴胺作为脑组织内一种重要的神经递质在细胞膜内外需要做合适的迁移,发挥其功能.多巴胺在细胞膜中扩散和透过过程的分子动力学涉及到多巴胺分子保护通道的畅通,与精神分裂症等病症有关.本文采用1-棕榈酰-2-油酰-卵磷脂(POPC)双层膜模拟细胞膜,通过分子动力学模拟获得多巴胺分子在细胞膜中和透过细胞膜运动自由能变化,探讨多巴胺在细胞膜中扩散和透过过程的分子动力学.多巴胺分子在POPC磷脂双层膜中间层做扩散运动的自由能变化为10-54 kJ mol-1(310 K),显示多巴胺分子在细胞膜中间层很容易横向和纵向扩散,保持多巴胺保护通道的畅通.多巴胺分子不容易透过POPC磷脂双层膜,因为透过过程自由能能垒为117-125 kJ mol-1(310 K).因此,人脑组织神经细胞里生产的多巴胺分子可以储藏在生物细胞膜空间.而过量的多巴胺则可以通过保护通道进入磷脂双层膜结构中间,做横向和纵向扩散运动,并且透过细胞膜,避免精神分裂症的发生.生物细胞膜的正常功能对于保持多巴胺保护通道的畅通和避免精神分裂症的出现都是重要的.研究结果与其它实验观察和结果相一致.

Dopamine, which is an important neural transmitter in brain tissue, needs to move freely within and through call membranes to fulfill its function. The molecular dynamics of dopamine diffusion within and permeation through, call membranes are involved in smoothing dopamine molecular protective channels, associated with schizophrenia and Parkinson＇s disease. In the present work, using a 1- palmitoyl- 2- oleoyl- glycero- 3- phosphatedylcholine （POPC） phospholipid bilayer membrane to model the cell membrane, we obtained the free- energy changes （AG） for dopamine diffusion within and permeation through the cell membrane, using molecular dynamics simulations, and probed the molecular dynamics of dopamine diffusion and permeation. The obtained values of AG for dopamine diffusion within the cell membrane were 10-54 kJ. mol^-1 at 310 K, which implies that dopamine diffuses easily horizontally and vertically within the call membrane to protect smoothing of the protective channel. However, it is not easy for dopamine to permeate through the call membrane, because AG for this process was 117-125 k J-mol^-1 （310 K）. Superfluous dopamine passes through the dopamine molecular protective channel and enters the middle region of the phospholipid bilayer membrane, and then diffuses easily along the horizontal and vertical orientations within the cell membrane, even permeating through the cell membrane, preventing schizophrenia. It is therefore important for the normal function of a biological cell membrane to protect smoothing of dopamine molecular protective channels, preventing schizophrenia. These results are in agreement with other experimental observations.