López Cascales J J, García de la Torre J
Departamento de Química Física, Universidad de Murcia, Campus de Espinardo, Spain.
Biochim Biophys Acta. 1997 Dec 4;1330(2):145-56. doi: 10.1016/s0005-2736(97)00156-9.
We describe a series of molecular dynamics simulations performed on a model of charged lipid bilayer (dipalmitoylphosphatidylserine) and water, in presence of sodium and lithium ions, with an atomic detail. The structure of the lipid membranes was strongly affected by the presence of lithium, as manifested by the observation of a transition from a disordered to a gel state. Concerning the mechanism of such a transition, it was associated to the dehydration that we detected in the lipid-water interface in the presence of lithium. This dehydration introduced an increase in the lipid-lipid interactions, and as a consequence, a diminution of the disorder of the membrane. When both types of ions are present in the aqueous phase, lithium shown a special affinity for the lipid membrane displacing almost all the sodium ions toward the middle of the water layer. As a result, we observed remarkable differences in the atom and electric field distributions across the lipid membrane. Concerning the diffusion and orientation of water molecules across the lipid-water interface, we also observed a strong dependency of the type ion. On the other hand, the mobility and the hydration shell of lithium and sodium ions are strongly perturbed by the presence of the charged lipid bilayer. The lipid layer was responsible for a dehydration of the ions compared to bulk water. This dehydration was compensated by an increase of coordination number of the ions with the lipid oxygens. Also, the residence times of water in the first hydration shell of lithium and sodium ions are perturbed by the presence of the lipid membrane.
我们描述了一系列在存在钠离子和锂离子的情况下，对带电荷脂质双层（二棕榈酰磷脂酰丝氨酸）和水的模型进行的具有原子细节的分子动力学模拟。锂的存在对脂质膜的结构产生了强烈影响，这表现为观察到从无序态到凝胶态的转变。关于这种转变的机制，它与我们在锂存在下在脂质 - 水界面检测到的脱水有关。这种脱水导致脂质 - 脂质相互作用增加，结果膜的无序度降低。当水相中同时存在两种离子时，锂对脂质膜表现出特殊亲和力，将几乎所有钠离子驱向水层中部。结果，我们观察到跨脂质膜的原子和电场分布存在显著差异。关于水分子跨脂质 - 水界面的扩散和取向，我们还观察到对离子类型的强烈依赖性。另一方面，锂和钠离子的迁移率和水合壳层受到带电荷脂质双层存在的强烈扰动。与 bulk 水相比，脂质层导致离子脱水。这种脱水通过离子与脂质氧原子配位数的增加得到补偿。此外，脂质膜的存在扰乱了锂和钠离子第一水合壳层中水分子的停留时间。
