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Confined filaments in soft vesicles - the case of sickle red blood cells.
Soft Matter ( IF 2.9 ) Pub Date : 2019-11-21 , DOI: 10.1039/c9sm01872g
Arabinda Behera 1 , Gaurav Kumar , Anirban Sain
Affiliation  

Abnormal shapes of red blood cells (RBC) have been associated with various diseases. Diverse RBC shapes have also been intriguing for membrane biophysics. Here we focus on sickle shaped RBC which form due to abnormal growth of semi-rigid hemoglobin (HbS) fibers confined in RBC. Using the area difference elasticity (ADE) model for RBC and worm-like chain model for the confined HbS fibers, we explore shape deformations at equilibrium using Monte-Carlo simulations. We show that while a single HbS fiber is not rigid enough to produce sickle like deformation, a fiber bundle can do so. We also consider multiple disjoint filaments and find that confinement can generate multipolar RBC shapes and can even promote helical filament conformations which have not been discussed before. We show that the same model, when applied to microtubules confined in phospholipid vesicles, predicts vesicle tubulation. In addition we reproduce the tube collapse transition and tennis racket type vesicle shapes, as reported in experiments. We conclude that with a decrease in the surface area to volume ratio, and membrane rigidity, the vesicles prefer tubulation over sickling. The highlight of this work is several important non-axisymmetric RBC and vesicle shapes, which have never been explored in simulations.

中文翻译:

软囊中的密闭丝-镰状红细胞。

红细胞形状异常与各种疾病有关。多种RBC形状也吸引了膜生物物理学的兴趣。在这里,我们重点介绍镰刀形RBC,它是由于限制在RBC中的半刚性血红蛋白(HbS)纤维异常生长而形成的。使用RBC的面积差弹性(ADE)模型和受限HbS纤维的蠕虫状链模型,我们使用蒙特卡洛模拟研究了平衡状态下的形状变形。我们显示出,虽然单根HbS纤维的刚性不足以产生镰刀状的变形,但纤维束却可以做到。我们还考虑了多个不相交的细丝,并发现封闭可以产生多极的RBC形状,甚至可以促进螺旋形的细丝构象,这在以前没有讨论过。我们证明了相同的模型,当将其应用于限制在磷脂囊泡中的微管时,可预测囊泡的形成。另外,如实验中所报道的,我们再现了管塌陷过渡和网球拍类型的囊泡形状。我们得出的结论是,随着表面积与体积之比的减小以及膜的硬度的降低,囊泡比镰刀更喜欢输卵管。这项工作的重点是一些重要的非轴对称RBC和囊泡形状,在仿真中从未探索过。
更新日期:2019-11-21
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