Jurkiewicz Piotr, Cwiklik Lukasz, Vojtíšková Alžběta, Jungwirth Pavel, Hof Martin
Academy of Sciences of the Czech Republic, Prague 8, Czech Republic.
Biochim Biophys Acta. 2012 Mar;1818(3):609-16. doi: 10.1016/j.bbamem.2011.11.033. Epub 2011 Dec 6.
Effects of alkali metal chlorides on the properties of mixed negatively charged lipid bilayers are experimentally measured and numerically simulated. Addition of 20mol% of negatively charged phosphatidylserine to zwitterionic phosphatidylcholine strengthens adsorption of monovalent cations revealing their specificity, in the following order: Cs(+)<K(+)<Na(+). Time-resolved fluorescence solvent relaxation shows significant decrease both in mobility and hydration of the lipid carbonyls probed by Laurdan upon addition of the cations. The experimental findings are supported by molecular dynamics simulations, which show deep penetration of the cations down to the glycerol level of the lipid bilayer where they pair with oxygen atoms of carbonyl groups (with pairing with sn-2 carbonyl being about twice stronger than pairing with the sn-1 one). Moreover, the cations bridge neighboring lipids forming clusters of up to 4 lipid molecules, which decreases the area per lipid, thickens the membrane, causes rising of lipid headgroups, and hinders lipid dynamics. All these effects follow the same Hofmeister ordering as the cationic adsorption to the bilayer.
实验测量并数值模拟了碱金属氯化物对混合负电荷脂质双层性质的影响。向两性离子磷脂酰胆碱中添加20mol%的带负电荷的磷脂酰丝氨酸会增强单价阳离子的吸附，揭示出它们的特异性，顺序如下：Cs(+) < K(+) < Na(+)。时间分辨荧光溶剂弛豫显示，添加阳离子后，由劳丹（Laurdan）探测的脂质羰基的流动性和水合作用均显著降低。分子动力学模拟支持了实验结果，模拟显示阳离子深入渗透到脂质双层的甘油水平，在那里它们与羰基的氧原子配对（与sn-2羰基的配对强度约为与sn-1羰基配对强度的两倍）。此外，阳离子桥接相邻脂质，形成多达4个脂质分子的簇，这会减小每个脂质的面积，使膜变厚，导致脂质头部基团上升，并阻碍脂质动力学。所有这些效应都遵循与阳离子在双层上吸附相同的霍夫迈斯特（Hofmeister）顺序。
