Pitman Michael C, Suits Frank, Gawrisch Klaus, Feller Scott E
IBM TJ Watson Research Center, Yorktown Heights, New York 10598, USA.
J Chem Phys. 2005 Jun 22;122(24):244715. doi: 10.1063/1.1899153.
We describe the dynamic behavior of a 1-stearoyl-2-oleoyl-phosphatidylethanolamine (SOPE) bilayer from a 20 ns molecular dynamics simulation. The dynamics of individual molecules are characterized in terms of (2)H spin-lattice relaxation rates, nuclear overhauser enhancement spectroscopy (NOESY) cross-relaxation rates, and lateral diffusion coefficients. Additionally, we describe the dynamics of hydrogen bonding through an analysis of hydrogen bond lifetimes and the time evolution of clusters of hydrogen bonded lipids. The simulated trajectory is shown to be consistent with experimental measures of internal, intermolecular, and diffusive motion. Consistent with our analysis of SOPE structure in the companion paper, we see hydrogen bonding dominating the dynamics of the interface region. Comparison of (2)H T(1) relaxation rates for chain methylene segments in phosphatidylcholine and phosphatidylethanolamine bilayers indicates that slower motion resulting from hydrogen bonding extends at least three carbons into the hydrophobic core. NOESY cross-relaxation rates compare well with experimental values, indicating the observed hydrogen bonding dynamics are realistic. Calculated lateral diffusion rates (4 +/ -1 x 10(-8) cm(2)s) are comparable, though somewhat lower than, those determined by pulsed field gradient NMR methods.
我们通过20纳秒的分子动力学模拟描述了1-硬脂酰-2-油酰基磷脂酰乙醇胺（SOPE）双层的动态行为。单个分子的动力学通过（2）H自旋晶格弛豫率、核Overhauser增强光谱（NOESY）交叉弛豫率和横向扩散系数来表征。此外，我们通过分析氢键寿命和氢键结合脂质簇的时间演化来描述氢键的动力学。模拟轨迹显示与内部、分子间和扩散运动的实验测量结果一致。与我们在配套论文中对SOPE结构的分析一致，我们发现氢键主导了界面区域的动力学。磷脂酰胆碱和磷脂酰乙醇胺双层中链亚甲基段的（2）H T（1）弛豫率比较表明，氢键导致的较慢运动至少延伸到疏水核心的三个碳原子处。NOESY交叉弛豫率与实验值比较良好，表明观察到的氢键动力学是真实的。计算得到的横向扩散率（4±1×10（-8）cm2/s）与脉冲场梯度NMR方法测定的结果相当，尽管略低一些。
