Conformational dynamics and phase behavior of lipid vesicles in a precisely controlled extensional flow
Conformational dynamics and phase behavior of lipid vesicles in a precisely controlled extensional flow
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精确控制的拉伸流中脂质囊泡的构象动力学和相行为
DOI：
10.1039/c9sm02048a
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发表时间：
2020
期刊：
影响因子：
3.4
通讯作者：
Schroeder, Charles M.
中科院分区：
文献类型：
--
作者：
Kumar, Dinesh;Richter, Channing M.;Schroeder, Charles M.
脂囊泡在基本生物过程中发挥着关键作用。尽管最近取得了进展，但由于长期观察强流中的形状波动带来的挑战，我们对囊泡的非平衡动力学缺乏完整的了解。在这项工作中，我们使用斯托克斯陷阱展示了平面拉伸流中囊泡形状和构象转变的流动相图，这使得能够控制精确定义的流中单个或多个囊泡的质心位置[A. Shenoy，C. V. Rao 和 C. M. Schroeder，Proc。国家。阿卡德。科学。美国，2016，113(15)，3976–3981]。通过这种方式，我们直接观察脂质囊泡的非平衡构象作为减少体积ν、毛细管数Ca和粘度对比λ的函数。我们的结果表明，拉伸流中的囊泡动力学特征在于出现三种不同的形状转变，包括管状到对称哑铃状转变、球状到不对称哑铃状转变以及准球形到椭球状转变。实验相图与最近的模拟预测非常吻合 [V. Narsimhan, A. P. Spann 和 E. S. Shaqfeh, J. Fluid Mech., 2014, 750, 144]。我们进一步表明，囊泡形状转变的相界与粘度对比度无关。总而言之，我们的结果证明了斯托克斯陷阱对于精确量化精确定义的流中囊泡拉伸动力学的实用性。
Lipid vesicles play a key role in fundamental biological processes. Despite recent progress, we lack a complete understanding of the non-equilibrium dynamics of vesicles due to challenges associated with long-time observation of shape fluctuations in strong flows. In this work, we present a flow-phase diagram for vesicle shape and conformational transitions in planar extensional flow using a Stokes trap, which enables control over the center-of-mass position of single or multiple vesicles in precisely defined flows [A. Shenoy, C. V. Rao and C. M. Schroeder, Proc. Natl. Acad. Sci. U. S. A., 2016, 113(15), 3976–3981]. In this way, we directly observe the non-equilibrium conformations of lipid vesicles as a function of reduced volume ν, capillary number Ca, and viscosity contrast λ. Our results show that vesicle dynamics in extensional flow are characterized by the emergence of three distinct shape transitions, including a tubular to symmetric dumbbell transition, a spheroid to asymmetric dumbbell transition, and quasi-spherical to ellipsoid transition. The experimental phase diagram is in good agreement with recent predictions from simulations [V. Narsimhan, A. P. Spann and E. S. Shaqfeh, J. Fluid Mech., 2014, 750, 144]. We further show that the phase boundary of vesicle shape transitions is independent of the viscosity contrast. Taken together, our results demonstrate the utility of the Stokes trap for the precise quantification of vesicle stretching dynamics in precisely defined flows.