The surface of a cell is crowded with membrane proteins. The size, shape, density, and mobility of extracellular surface proteins mediate cell surface accessibility to external molecules, viral particles, and other cells. However, predicting these qualities is not always straightforward, even when protein structures are known. We previously developed an experimental method for measuring flow-driven lateral transport of neutravidin bound to biotinylated lipids in supported lipid bilayers. Here, we use this method to detect hydrodynamic force applied to a series of lipid-anchored proteins with increasing size. We find that the measured force reflects both protein size and shape, making it possible to distinguish these features of intact, folded proteins in their undisturbed orientation and proximity to the lipid membrane. In addition, our results demonstrate that individual proteins are transported large distances by flow forces on the order of femtoNewtons, similar in magnitude to the shear forces resulting from blood circulation or from the swimming motion of microorganisms. Similar protein transport across living cells by hydrodynamic force may contribute to biological flow sensing.

中文翻译：

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脂质锚定蛋白大小和形状的微流体测量


细胞表面挤满了膜蛋白。细胞外表面蛋白的大小、形状、密度和迁移率介导细胞表面对外部分子、病毒颗粒和其他细胞的可及性。然而，即使蛋白质结构已知，预测这些特性也并不总是那么简单。我们之前开发了一种实验方法，用于测量与支撑脂质双层中生物素化脂质结合的中性亲和素的流动驱动的横向运输。在这里，我们使用这种方法来检测施加在一系列尺寸增加的脂质锚定蛋白质上的流体动力。我们发现测得的力反映了蛋白质的大小和形状，从而可以在它们不受干扰的方向和靠近脂质膜的位置上区分完整折叠蛋白质的这些特征。此外，我们的结果表明，单个蛋白质通过飞牛顿量级的流力远距离传输，其大小类似于血液循环或微生物游泳运动产生的剪切力。通过流体动力在活细胞中传递类似的蛋白质可能有助于生物流动感应。