Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States.
Department of Medicine, University of Arizona, Tucson, Arizona 85721, United States.
Langmuir. 2022 Jan 11;38(1):100-111. doi: 10.1021/acs.langmuir.1c02098. Epub 2021 Dec 30.
Polymerization enhances the stability of a planar supported lipid bilayer (PSLB) but it also changes its chemical and mechanical properties, attenuates lipid diffusion, and may affect the activity of integral membrane proteins. Mixed bilayers composed of fluid lipids and poly(lipids) may provide an appropriate combination of polymeric stability coupled with the fluidity and elasticity needed to maintain the bioactivity of reconstituted receptors. Previously (, , , 12483-12491) we showed that binary mixtures of the polymerizable lipid bis-SorbPC and the fluid lipid DPhPC form phase-segregated PSLBs composed of nanoscale fluid and poly(lipid) domains. Here we used atomic force microscopy (AFM) to compare the nanoscale mechanical properties of these binary PSLBs with single-component PSLBs. The elastic (Young's) modulus, area compressibility modulus, and bending modulus of bis-SorbPC PSLBs increased upon polymerization. Before polymerization, breakthrough events at forces below 5 nN were observed, but after polymerization, the AFM tip could not penetrate the PSLB up to an applied force of 20 nN. These results are attributed to the polymeric network in poly(bis-SorbPC), which increases the bilayer stiffness and resists compression and bending. In binary DPhPC/poly(bis-SorbPC) PSLBs, the DPhPC domains are less stiff, more compressible, and are less resistant to rupture and bending compared to pure DPhPC bilayers. These differences are attributed to bis-SorbPC monomers and oligomers present in DPhPC domains that disrupt the packing of DPhPC molecules. In contrast, the poly(bis-SorbPC) domains are stiffer and less compressible relative to pure PSLBs; this difference is attributed to DPhPC filling the nm-scale pores in the polymerized domains that are created during bis-SorbPC polymerization. Thus, incomplete phase segregation increases the stability of poly(bis-SorbPC) but has the opposite, detrimental effect for DPhPC. Overall, these results provide guidance for the design of partially polymerized bilayers for technological uses.
聚合作用增强了平面支撑脂质双层（PSLB）的稳定性，但也改变了其化学和机械性质，减弱了脂质的扩散，并可能影响整合膜蛋白的活性。由流体脂质和聚（脂质）组成的混合双层可能提供聚合稳定性的适当组合，同时具有维持重建受体生物活性所需的流动性和弹性。先前（，，，12483-12491）我们表明，可聚合脂质双 SorbPC 与流体脂质 DPhPC 的二元混合物形成由纳米级流体和聚（脂质）域组成的相分离 PSLB。在这里，我们使用原子力显微镜（AFM）比较了这些二元 PSLB 与单一组分 PSLB 的纳米级机械性质。双 SorbPC PSLB 的弹性（杨氏）模量、面积压缩模量和弯曲模量在聚合作用下增加。在聚合之前，在低于 5 nN 的力下观察到突破事件，但在聚合之后，AFM 探针在应用力高达 20 nN 时无法穿透 PSLB。这些结果归因于聚（双 SorbPC）中的聚合网络，该网络增加了双层的刚度并抵抗压缩和弯曲。在二元 DPhPC/聚（双 SorbPC）PSLB 中，与纯 DPhPC 双层相比，DPhPC 域的刚性较小，可压缩性较大，并且更易破裂和弯曲。这些差异归因于存在于 DPhPC 域中的双 SorbPC 单体和低聚物，这些单体和低聚物破坏了 DPhPC 分子的堆积。相比之下，与纯 PSLB 相比，聚（双 SorbPC）域的刚性较大且可压缩性较小；这种差异归因于 DPhPC 填充了在双 SorbPC 聚合过程中形成的聚合域中的纳米级孔。因此，不完全的相分离增加了聚（双 SorbPC）的稳定性，但对 DPhPC 则产生相反的有害影响。总的来说，这些结果为部分聚合双层的设计提供了指导，以满足技术用途的需要。
