Misuraca Loreto, LoRicco Josephine, Oger Philippe, Peters Judith, Demé Bruno
Univ. Grenoble Alpes, CNRS, LIPhy, 38000 Grenoble, France; Institut Laue Langevin, F-38042 Grenoble Cedex 9, France.
INSA Lyon, Université de Lyon, CNRS, UMR5240, Villeurbanne, France.
Biochim Biophys Acta Biomembr. 2023 Mar;1865(3):184119. doi: 10.1016/j.bbamem.2023.184119. Epub 2023 Jan 10.
Protomembranes at the origin of life were likely composed of short-chain lipids, readily available on the early Earth. Membranes formed by such lipids are less stable and more permeable under extreme conditions, so a novel membrane architecture was suggested to validate the accuracy of this assumption. The model membrane includes the presence of a layer of alkanes in the mid-plane of the protomembrane in between the two monolayer leaflets and lying perpendicular to the lipid acyl chains. Here, we investigated such a possibility experimentally for membranes formed by the short-chain phospholipid 1,2-didecanoyl-sn-glycero-3-phophocholine, including or not the alkanes eicosane, squalane or triacontane by means of neutron membrane diffraction and contrast variation. We found strong indications for incorporation of two of the three alkanes in the membrane mid-plane through the determination of neutron scattering length density profiles with hydrogenated vs deuterated alkanes and membrane swelling at various relative humidities indicating a slightly increased bilayer thickness when the alkanes are incorporated into the bilayers. The selectivity of the incorporation points out the role of the length of the n-alkanes with respect to the capacity of the membrane to incorporate them.
生命起源时的原始膜可能由早期地球上易于获得的短链脂质组成。由这类脂质形成的膜在极端条件下稳定性较差且渗透性更强，因此有人提出一种新型膜结构来验证这一假设的准确性。该模型膜包括在原始膜的中间平面、两个单分子层小叶之间且垂直于脂质酰基链的一层烷烃。在此，我们通过中子膜衍射和对比变化实验研究了由短链磷脂1,2 - 二癸酰 - sn - 甘油 - 3 - 磷酸胆碱形成的膜（包括或不包括正二十烷、角鲨烷或三十烷等烷烃）的这种可能性。通过使用氢化与氘化烷烃测定中子散射长度密度分布以及在不同相对湿度下膜的膨胀情况，我们发现有强有力的迹象表明三种烷烃中的两种被纳入膜中间平面，这表明当烷烃被纳入双层膜时双层膜厚度略有增加。这种纳入的选择性指出了正构烷烃长度对于膜纳入它们的能力的作用。
