作者：Yong-Hao Ma, Bolin Li, Jingjing Yang, Xiaofeng Han, Zhan Chen*, Xiaolin Lu*
关键字：SFG, lipid, size effects, metal ions, flip-flop
论文来源：期刊
具体来源：J. Phys. Chem. C 2019, 12329, 17899-17907
发表时间：2019年

Ion homeostasis regulated by diverse transport systems is important for cell functions, where the two major components of cell membranes, namely proteins and lipids, must play critical roles. The role of transport systems based on proteins, for example ion pumps and channels, has generally been acknowledged and studied in the past few decades, while the importance of lipid systems, for example lipid ion channels, has not been fully appreciated so far with the lack of detailed molecular-level information. Here, we applied sum frequency generation vibrational spectroscopy to investigate the lipid transmembrane movement, namely flip-flop, affected by metal ions for lipid bilayers, which is related to the cellular ion homeostasis. Metal ions in the same group (Ba2+, Sr2+, and Ca2+) but with different sizes were used; the distance between lipid molecules in a bilayer was also manipulated upon adjusting the surface pressure. We found that, on the one hand, there existed a match relationship between the metal ion size and the distance among the lipid molecules, which led to the significant decrease of the flip-flop rate for the lipid bilayer. On the other hand, the flip-flop process was accelerated when the metal ion size and the lipid distance were mismatched. This study highlights the ion size effects on the lipid transmembrane flip-flop rates, providing the inspiring clue for understanding the lipid function related to the cellular ion homeostasis.

https://pubs.acs.org/doi/10.1021/acs.jpcc.9b04557