Abstract

We have studied changes in the structural parameters of 1,2-dimyristoyl-sn-3-phosphocholine (DMPC) unilamellar vesicles at a concentration series 0–30 mM of divalent metal cations Ca²⁺, Mg²⁺, and Co²⁺ by means of small-angle neutron scattering (SANS). The membrane structural parameters (thickness and area per lipid) were obtained at different concentrations of cations in the gel and fluid phases of membrane. Both Ca²⁺ and Mg²⁺ ions at the concentrations of 0–1 mM increase the membrane thickness by 1.9 Å and 2.9 Å in the fluid and gel phase, respectively. In the concentration range of 1–30 mM, either a weak tendency to a thickness decrease of ~ 1 Å is observed, or the thickness does not change at all. In the case of Co²⁺ ions, all changes are extremely weak. We advocate a model of electrostatic interactions for these systems that encompasses the formation of ion bridges between lipid headgroups. Using the Langmuir adsorption isotherm we estimate the fraction of Ca²⁺ ions bound to the DMPC membrane. The developed model is of an interest to the future studies of membrane interactions with various charged peptides, such as those from the amyloid-β family.

中文翻译：

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二价离子对二肉豆蔻酰磷脂酰胆碱囊泡中双层结构的影响

摘要

我们研究了浓度为0–30 mM的二价金属阳离子Ca 2 ⁺，Mg ²⁺和Co ²⁺的浓度系列时，1,2-二肉豆蔻酰基-sn-3-磷酸胆碱（DMPC）单层囊泡的结构参数的变化，通过小角度中子散射（SANS）的手段。在不同浓度的阳离子在膜的凝胶相和流体相中获得膜结构参数（厚度和每脂质面积）。Ca ²⁺和Mg ²⁺在流体和凝胶相中，浓度为0-1 mM的离子分别使膜厚度增加1.9Å和2.9Å。在1–30 mM的浓度范围内，观察到厚度减小约1Å的趋势很弱，或者厚度根本没有变化。对于Co ²⁺离子，所有变化都非常微弱。我们提倡这些系统的静电相互作用模型，该模型包括脂质头基之间离子桥的形成。使用Langmuir吸附等温线，我们估计与DMPC膜结合的Ca ²⁺离子的比例。所开发的模型对于未来与各种带电肽（如来自淀粉样β家族的带电肽）的膜相互作用的研究感兴趣。