Department of Medical and Biological Physics, Technical University Dortmund, 44227 Dortmund, Germany
Proc Natl Acad Sci U S A. 2022 Feb 22;119(8). doi: 10.1073/pnas.2117521119.
The origin of nonlinear responses in cells has been suggested to be crucial for various cell functions including the propagation of the nervous impulse. In physics, nonlinear behavior often originates from phase transitions. Evidence for such transitions on the single-cell level, however, has so far not been provided, leaving the field unattended by the biological community. Here, we demonstrate that single cells of a human neuronal cell line display all optical features of a sharp, highly nonlinear phase transition within their membrane. The transition is reversible and does not originate from protein denaturation. Triggered by temperature and modified by pH here, a thermodynamic approach strongly suggests that similar nonlinear state changes can be induced by other variables such as calcium or mechanical stress. At least in lipid membranes, such state changes are accompanied by significant changes in permeability, enzyme activity, elastic, and electrical properties.
细胞中非线性响应的起源被认为对各种细胞功能至关重要，包括神经冲动的传播。在物理学中，非线性行为通常源于相变。然而，到目前为止，还没有提供关于单细胞水平上这种转变的证据，这使得生物学界对其关注不足。在这里，我们证明了人类神经元细胞系的单个细胞在其膜内表现出尖锐的、高度非线性相变的所有光学特征。该转变是可逆的，并非源于蛋白质变性。受温度触发并由 pH 值改变，热力学方法强烈表明，类似的非线性状态变化可以由其他变量如钙或机械应力来诱导。至少在脂质膜中，这种状态变化伴随着通透性、酶活性、弹性和电学性质的显著变化。
