Caritá Amanda C, Cavalcanti Rafaela R M, Oliveira Mariana S S, Riske Karin A
Universidade Federal de São Paulo, Department of Biophysics, São Paulo, Brazil.
Universidade Federal de São Paulo, Department of Biophysics, São Paulo, Brazil.
Chem Phys Lipids. 2023 Sep;255:105327. doi: 10.1016/j.chemphyslip.2023.105327. Epub 2023 Jul 11.
Detergents are amphiphilic molecules often used to solubilize biological membranes and separate their components. Here we investigate the solubilization of lipid vesicles by the commonly used non-ionic detergents polyoxyethylene (20) oleyl ether (Brij 98), n-octyl-β-D-glucoside (OG), and n-dodecyl β-D maltoside (DDM) and compare the results with the standard detergent Triton X-100 (TX-100). The vesicles were composed of palmitoyl oleoyl phosphatidylcholine (POPC) or of a biomimetic ternary mixture of POPC, egg sphingomyelin (SM) and cholesterol (2:1:2 molar ratio). To follow the solubilization profile of large unilamellar vesicles (LUVs), 90° light scattering measurements were done along the titration of LUVs with the detergents. Then, giant unilamellar vesicles (GUVs) were observed with optical microscopy during exposure to the detergents, to allow direct visualization of the solubilization process. Isothermal titration calorimetry (ITC) was used to assess the binding constant of the detergents in POPC bilayers. The results show that the incorporation of TX-100, Brij 98 and, to a lesser extent, OG in the pure POPC liposomes leads to an increase in the vesicle area, which indicates their ability to redistribute between the two leaflets of the membrane in a short scale of time. On the other hand, DDM incorporates mainly in the external leaflet causing an increase in vesicle curvature/tension leading ultimately to vesicle burst. Only TX-100 and OG were able to completely solubilize the POPC vesicles, whereas the biomimetic ternary mixture was partially insoluble in all detergents tested. TX-100 and OG were able to incorporate in the bilayer of the ternary mixture and induce macroscopic phase separation of liquid-ordered (Lo) and liquid-disordered (Ld) domains, with selective solubilization of the latter. Combination of ITC data with turbidity results showed that TX-100 and OG can be incorporated up to almost 0.3 detergent/lipid, significantly more than Brij 98 and DDM. This fact seems to be directly related to their higher capacity to solubilize POPC membranes and their ability to induce macroscopic phase separation in the biomimetic lipid mixture.
去污剂是两亲性分子，常用于溶解生物膜并分离其成分。在此，我们研究了常用的非离子去污剂聚氧乙烯（20）油醚（Brij 98）、正辛基-β-D-葡萄糖苷（OG）和正十二烷基-β-D-麦芽糖苷（DDM）对脂质囊泡的溶解作用，并将结果与标准去污剂吐温X-100（TX-100）进行比较。这些囊泡由棕榈酰油酰磷脂酰胆碱（POPC）或由POPC、鸡蛋鞘磷脂（SM）和胆固醇组成的仿生三元混合物（摩尔比为2:1:2）构成。为了跟踪大单层囊泡（LUVs）的溶解情况，在用去污剂滴定LUVs的过程中进行了90°光散射测量。然后，在暴露于去污剂的过程中用光学显微镜观察巨型单层囊泡（GUVs），以便直接观察溶解过程。等温滴定量热法（ITC）用于评估去污剂在POPC双层中的结合常数。结果表明，TX-100、Brij 98以及在较小程度上OG掺入纯POPC脂质体中会导致囊泡面积增加，这表明它们能够在短时间内在膜的两个小叶之间重新分布。另一方面，DDM主要掺入外部小叶，导致囊泡曲率/张力增加，最终导致囊泡破裂。只有TX-100和OG能够完全溶解POPC囊泡，而仿生三元混合物在所有测试的去污剂中部分不溶。TX-100和OG能够掺入三元混合物的双层中，并诱导液相有序（Lo）和液相无序（Ld）域的宏观相分离，后者被选择性溶解。ITC数据与浊度结果的结合表明，TX-100和OG最多可掺入近0.3的去污剂/脂质，明显多于Brij 98和DDM。这一事实似乎与它们溶解POPC膜的更高能力以及在仿生脂质混合物中诱导宏观相分离的能力直接相关。
