Department of Mechanical Engineering, University of Washington, Seattle, WA 98195-2600;
National Laboratory of Solid State Microstructures, Department of Physics, Nanjing University, Nanjing 210093, China;
Proc Natl Acad Sci U S A. 2014 Jul 8;111(27):E2780-6. doi: 10.1073/pnas.1402909111. Epub 2014 Jun 23.
Ferroelectricity has long been speculated to have important biological functions, although its very existence in biology has never been firmly established. Here, we present compelling evidence that elastin, the key ECM protein found in connective tissues, is ferroelectric, and we elucidate the molecular mechanism of its switching. Nanoscale piezoresponse force microscopy and macroscopic pyroelectric measurements both show that elastin retains ferroelectricity at 473 K, with polarization on the order of 1 μC/cm(2), whereas coarse-grained molecular dynamics simulations predict similar polarization with a Curie temperature of 580 K, which is higher than most synthetic molecular ferroelectrics. The polarization of elastin is found to be intrinsic in tropoelastin at the monomer level, analogous to the unit cell level polarization in classical perovskite ferroelectrics, and it switches via thermally activated cooperative rotation of dipoles. Our study sheds light onto a long-standing question on ferroelectric switching in biology and establishes ferroelectricity as an important biophysical property of proteins. This is a critical first step toward resolving its physiological significance and pathological implications.
铁电性长期以来被推测具有重要的生物学功能，尽管其在生物学中的存在从未被确凿证实。在这里，我们提出了令人信服的证据表明，弹性蛋白是结缔组织中关键的细胞外基质蛋白，具有铁电性，并阐明了其转变的分子机制。纳米级压电力显微镜和宏观 pyroelectric 测量都表明，弹性蛋白在 473 K 时保留铁电性，极化强度约为 1 μC/cm(2)，而粗粒分子动力学模拟预测类似的极化强度，居里温度为 580 K，高于大多数合成分子铁电体。在单体水平上，弹性蛋白的极化被发现是天然弹性蛋白的固有特性，类似于经典钙钛矿铁电体的单元胞极化，并且通过热激活偶极子的协同旋转来切换。我们的研究揭示了生物学中关于铁电切换的一个长期存在的问题，并确立了铁电性是蛋白质的一种重要生物物理特性。这是解决其生理意义和病理意义的关键的第一步。
