School of Physics, HH Wills Physics Laboratory, University of Bristol, BS8 1TL, UK.
Bristol Centre for Functional Nanomaterials, HH Wills Physics Laboratory, University of Bristol, BS8 1TL, UK.
Soft Matter. 2022 Mar 2;18(9):1747-1756. doi: 10.1039/d1sm01542g.
To accurately represent the morphological and elastic properties of a human red blood cell, Fu [Fu , , 2017, , 193-203] recently developed a coarse-grained molecular dynamics model with particular detail in the membrane. However, such a model accrues an extremely high computational cost for whole-cell simulation when assuming an appropriate length scaling - that of the bilayer thickness. To date, the model has only simulated "miniature" cells in order to circumvent this, with the assumption that these miniaturised cells correctly represent their full-sized counterparts. The present work assesses the validity of this approach, by testing the scale invariance of the model through simulating cells of various diameters; first qualitatively in their shape evolution, then quantitatively by measuring their bending rigidity through fluctuation analysis. Cells of diameter of at least 0.5 μm were able to form the characteristic biconcave shape of human red blood cells, though smaller cells instead equilibrated to bowl-shaped stomatocytes. Thermal fluctuation analysis showed the bending rigidity to be constant over all cell sizes tested, and consistent between measurements on the whole-cell and on a planar section of bilayer. This is as expected from the theory on both counts. Therefore, we confirm that the evaluated model is a good representation of a full-size RBC when the model diameter is ≥0.5 μm, in terms of the morphological and mechanical properties investigated.
为了准确地描述人类红细胞的形态和弹性特性，Fu [Fu,, 2017,, 193-203] 最近开发了一种具有细胞膜细节的粗粒度分子动力学模型。然而，当假设适当的长度缩放（即双层厚度）时，这种模型在整个细胞模拟中会产生极高的计算成本。迄今为止，该模型仅对“微型”细胞进行了模拟，以避免这种情况，假设这些微型化细胞能够正确代表其全尺寸对应物。本工作通过模拟不同直径的细胞来评估该方法的有效性，首先从形状演化的角度进行定性测试，然后通过波动分析测量其弯曲刚度进行定量测试。直径至少为 0.5μm 的细胞能够形成人类红细胞的特征双凹形，而较小的细胞则平衡为碗状的口形红细胞。热波动分析表明，在所有测试的细胞尺寸上，弯曲刚度都是恒定的，并且在整个细胞和双层平面部分的测量之间也是一致的。这从两个方面的理论来看都是合理的。因此，我们确认在模型直径≥0.5μm 的情况下，在所研究的形态和力学特性方面，评估的模型是全尺寸 RBC 的良好代表。
