Dynamics of intracellular diffusion under various intracellular spatial dimensions
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摘要: 扩散对于细胞内生物分子的运输至关重要，是各种生命过程的物理基础．由于细胞内部微环境的复杂性，其内部生物大分子的扩散呈现出异常扩散、空间异质性、各向异性等新奇动力学特性．然而，细胞内扩散动力学与胞内微环境空间维度之间的关系并不清楚．利用活细胞单分子荧光跟踪技术研究了细胞内量子点探针的扩散，定量分析了细胞内准二维扩散和丝状伪足内准一维扩散的动力学特征．研究发现相比于细胞内的准二维扩散，丝状伪足内的扩散速度更快，且扩散加速现象与丝状伪足的直径成反比，表明丝状伪足提供了一种更加有效的胞内物质运输途径．本研究不仅阐明了细胞内扩散动力学与胞内空间维度的关系，而且揭示了细胞通过亚细胞结构调控生物大分子运输的复杂机制．Abstract: Diffusion is crucial for biomolecule transportation in cells and is the physical basis for various life processes． Due to complexity of intracellular microenvironment, biomolecule diffusion inside cells exhibits novel dynamic characteristics such as anomalous diffusion, spatial heterogeneity, and anisotropy． The relationship between intracellular diffusion dynamics and spatial dimensions of intracellular microenvironment is not well understood． Live-cell single-molecule fluorescence tracking techniques were used in this study to investigate the diffusion of quantum dots inside cells, to quantitatively analyze dynamic features of intracellular quasi-two-dimensional diffusion and quasi-one-dimensional diffusion in filopodia． Compared to intracellular quasi-two-dimensional diffusion, diffusion within filopodia was found to exhibit higher rate, and the phenomenon of diffusion acceleration was inversely proportional to the diameter of the filopodia, suggesting that the filopodia is a more efficient pathway for intracellular substance transport． The relationship between intracellular diffusion dynamics and spatial dimensions of intracellular environment is elucidated, mechanisms of cellular regulation of biomolecule transport through subcellular structures are clarified．
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Key words:
- diffusion /
- spatial dimension /
- filopodium /
- single molecule tracking
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图 1 细胞内准一维和准二维的扩散现象
a. 导入量子点QD655的A549细胞明场图像；b. 导入量子点QD655的A549细胞荧光场图像；c. 导入于细胞内>40帧的全部量子点轨迹，浅蓝色方框圈出的为部分细胞中心准二维扩散的量子点轨迹，黄色方框圈出的为部分丝状伪足内准一维扩散的量子点轨迹；d. 丝状伪足内的量子点运动轨迹（左）和细胞内的量子点运动轨迹（右）．
图 2 细胞内准一维和准二维扩散在x和y方向的均方位移
a.丝状伪足内准一维扩散在x和y方向的均方位移（轨迹数：689）；b. 细胞内准二维扩散在x和y方向的均方位移（轨迹数：362）．
图 3 细胞内准一维和准二维扩散的均方位移分析
a. 丝状伪足内准一维扩散在x和y方向的扩散速率；b. 细胞内准二维扩散在x和y方向的扩散速率；c. 丝状伪足内准一维扩散在x和y方向的运动模式；d. 细胞内准二维扩散在x和y方向的运动模式．
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