Matsuoka Satomi, Shibata Tatsuo, Ueda Masahiro
Laboratories for Nanobiology, Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan.
Biophys J. 2009 Aug 19;97(4):1115-24. doi: 10.1016/j.bpj.2009.06.007.
Single-molecule trajectories of molecules on the membrane of living cells have indicated the possibility that the lateral mobility of individual molecules is variable with time. Such temporal variation in mobility may indicate intrinsic kinetics of multiple molecular states. To clarify the mechanisms of signal processing on the membrane, quantitative characterizations of such temporal variations are necessary. Here we propose a method to analyze and characterize the multiple states in lateral mobility and their transition kinetics from single-molecule trajectories based on a displacement probability density function and an autocorrelation function of squared displacements. We performed our method for three cases: a molecule with a single diffusion coefficient (D), a mixture of molecules in two states with different D-values, and a molecule switching between two states with different D-values. Our analysis of numerically generated trajectories successfully distinguished the three cases and estimated the characteristic parameters for mobility and the kinetics of state transitions. This method is applicable to single-molecule tracking analysis of molecules in multiple functional states with different lateral mobility on the membrane of living cells.
活细胞细胞膜上分子的单分子轨迹表明，单个分子的侧向移动性可能随时间变化。这种移动性的时间变化可能表明多种分子状态的内在动力学。为了阐明细胞膜上信号处理的机制，有必要对这种时间变化进行定量表征。在此，我们提出一种基于位移概率密度函数和平方位移自相关函数，从单分子轨迹分析和表征侧向移动性中的多种状态及其转移动力学的方法。我们针对三种情况应用了该方法：具有单一扩散系数（D）的分子、处于两种具有不同D值状态的分子混合物，以及在两种具有不同D值状态之间切换的分子。我们对数值生成轨迹的分析成功区分了这三种情况，并估计了移动性的特征参数和状态转变的动力学。该方法适用于对活细胞细胞膜上具有不同侧向移动性的多种功能状态分子进行单分子跟踪分析。
