Phase Transitions in Small Isotropic Bicelles,Langmuir

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Phase Transitions in Small Isotropic Bicelles
Langmuir ( IF 3.7 ) Pub Date : 2018-02-27 00:00:00 , DOI: 10.1021/acs.langmuir.7b03610
Erik F. Kot _{1,

2} , Sergey A. Goncharuk _{1,

3} , Alexander S. Arseniev _{1,

2} , Konstantin S. Mineev _{1,

2}

Affiliation

Isotropic phospholipid bicelles are one of the most prospective membrane mimetics for the structural studies of membrane proteins in solution. Recent works provided an almost full set of data regarding the properties of isotropic bicelles; however, one major aspect of their behavior is still under consideration: the possible mixing between the lipid and detergent in the bilayer area. This problem may be resolved by studying the lipid phase transitions in bicelle particles. In the present work, we investigate two effects: phase transitions of bilayer lipids and temperature-induced growth of isotropic bicelles using the NMR spectroscopy. We propose an approach to study the phase transitions in isotropic bicelles based on the properties of ³¹P NMR spectra of bilayer-forming lipids. We show that phase transitions in small bicelles are “fractional”, particles with the liquid-crystalline and gel bilayers coexist in solution at certain temperatures. We study the effects of lipid fatty chain type and demonstrate that the behavior of various lipids in bilayers is reproduced in the isotropic bicelles. We show that the temperature-induced growth of isotropic bicelles is not related directly to the phase transition but is the result of the reversible fusion of bicelle particles. In accordance with our data, rim detergents also have an impact on phase transitions: detergents that resist the temperature-induced growth provide the narrowest and most expressed transitions at higher temperatures. We demonstrate clearly that phase transitions take place even in the smallest bicelles that are applicable for structural studies of membrane proteins by solution NMR spectroscopy. This last finding, together with other data draws a thick line under the long-lasting argument about the relevance of small isotropic bicelles. We show with certainty that the small bicelles can reproduce the most fundamental property of lipid membranes: the ability to undergo phase transition.

中文翻译：

各向同性小型单体电池的相变

各向同性磷脂双细胞是溶液中膜蛋白结构研究的最有前途的膜模拟物之一。最近的工作提供了关于各向同性单体电池特性的几乎完整的数据集。然而，它们行为的一个主要方面仍在考虑中：在双层区域中脂质和去污剂之间可能的混合。这个问题可以通过研究比塞尔颗粒中的脂质相变来解决。在目前的工作中，我们使用NMR光谱研究了两种效应：双层脂质的相变和温度诱导的各向同性单晶细胞的生长。我们提出了一种方法来研究各向同性Bicell的相变，基于³¹的性质双层形成脂质的1 H NMR光谱。我们表明，在较小的Bicell中，相变是“分数”的，在一定温度下，具有液晶和凝胶双层的颗粒共存于溶液中。我们研究脂质脂肪链类型的影响，并证明在各向同性Bicelles中重现双层中各种脂质的行为。我们表明，温度诱导的各向同性Bicelles的增长与相变不直接相关，而是比可可颗粒可逆融合的结果。根据我们的数据，轮缘清洁剂还会对相变产生影响：抵抗温度引起的生长的清洁剂在较高温度下提供最狭窄和最明确表达的过渡。我们清楚地表明，即使在适用于通过溶液NMR光谱对膜蛋白进行结构研究的最小单体池中，也会发生相变。在关于小各向同性Bicell的相关性的长期争论下，这一最后发现与其他数据一起划出了一条粗线。我们可以肯定地表明，小细胞可以重现脂质膜的最基本特性：经历相变的能力。

更新日期：2018-02-27

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