Misuraca Loreto, Caliò Antonino, LoRicco Josephine G, Hoffmann Ingo, Winter Roland, Demé Bruno, Peters Judith, Oger Philippe M
University Grenoble Alpes, CNRS, LIPhy, 38000 Grenoble, France.
Institut Laue Langevin, 38042 Grenoble, France.
Life (Basel). 2022 Mar 17;12(3):445. doi: 10.3390/life12030445.
One of the first steps in the origin of life was the formation of a membrane, a physical boundary that allowed the retention of molecules in concentrated solutions. The proto-membrane was likely formed by self-assembly of simple readily available amphiphiles, such as short-chain fatty acids and alcohols. In the commonly accepted scenario that life originated near hydrothermal systems, how these very simple membrane bilayers could be stable enough in time remains a debated issue. We used various complementary techniques such as dynamic light scattering, small angle neutron scattering, neutron spin-echo spectroscopy, and Fourier-transform infrared spectroscopy to explore the stability of a novel protomembrane system in which the insertion of alkanes in the midplane is proposed to shift membrane stability to higher temperatures, pH, and hydrostatic pressures. We show that, in absence of alkanes, protomembranes transition into lipid droplets when temperature increases; while in presence of alkanes, membranes persist for longer times in a concentration-dependent manner. Proto-membranes containing alkanes are stable at higher temperatures and for longer times, have a higher bending rigidity, and can revert more easily to their initial state upon temperature variations. Hence, the presence of membrane intercalating alkanes could explain how the first membranes could resist the harsh and changing environment of the hydrothermal systems. Furthermore, modulating the quantity of alkanes in the first membranes appears as a possible strategy to adapt the proto-membrane behavior according to temperature fluctuations, and it offers a first glimpse into the evolution of the first membranes.
生命起源的最初步骤之一是形成膜，这是一种物理边界，可使分子保留在浓缩溶液中。原始膜可能是由简单易得的两亲分子自组装形成的，例如短链脂肪酸和醇。在普遍接受的生命起源于热液系统附近的设想中，这些非常简单的膜双层如何能及时保持足够的稳定性仍是一个有争议的问题。我们使用了各种互补技术，如动态光散射、小角中子散射、中子自旋回波光谱和傅里叶变换红外光谱，来探索一种新型原始膜系统的稳定性，在该系统中，烷烃插入膜中间平面被认为可将膜的稳定性转移到更高的温度、pH值和静水压力条件下。我们发现，在没有烷烃的情况下，当温度升高时原始膜会转变为脂滴；而在有烷烃存在时，膜会以浓度依赖的方式持续更长时间。含有烷烃的原始膜在更高温度下能保持更长时间的稳定，具有更高的弯曲刚度，并且在温度变化时能更容易恢复到初始状态。因此，膜间插入烷烃的存在可以解释最初的膜如何能够抵御热液系统恶劣多变的环境。此外，调节最初膜中烷烃的数量似乎是一种根据温度波动来调整原始膜行为的可能策略，它为最初膜的进化提供了初步的见解。
