Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, PA 19122, USA.
Present address: Pacific Northwest National Laboratory, Richland, WA 99352, USA.
Angew Chem Int Ed Engl. 2022 Oct 17;61(42):e202205608. doi: 10.1002/anie.202205608. Epub 2022 Sep 14.
Phase transitions of lipid bilayer membranes should affect passive transport of molecules. While this hypothesis has been used to design drug-releasing thermosensitive liposomes, the effect has yet to be quantified. Herein, we use time-resolved second harmonic light scattering to measure transport of a molecular cation across membranes of unilamellar liposomes composed of the total lipid extract of E. coli from 9 °C to 36 °C, in which two distinct phase transitions (gel to liquid-disordered phase) have been identified. While the transport rate slowly increases with temperature as a diffusion process, dramatic jumps are observed at 14.7 °C and 27.6 °C, the known phase transitions. The transport rate constant measured as (7.3±0.8)×10 s in the liquid-disordered phase at 36 °C is 35-times faster than (2.1±0.2)×10 s of the gel phase at 9 °C. For the mixed-phase between these two phases, the measured rates are consistent with a structure of gel domains among a liquid-disordered bulk.
脂质双层膜的相变应该会影响分子的被动运输。虽然这一假设已被用于设计释放药物的热敏脂质体，但这一效应尚未被量化。在此，我们使用时间分辨二次谐波光散射技术来测量由大肠杆菌总脂提取物组成的单层脂质体的分子阳离子的跨膜运输，其中已鉴定出两种不同的相变（凝胶到无序相）。尽管作为扩散过程，运输速率随温度缓慢增加，但在 14.7°C 和 27.6°C 时，即已知的相变温度，观察到了显著的跳跃。在 36°C 的无序相中测量到的传输速率常数为(7.3±0.8)×10 s，比在 9°C 的凝胶相中(2.1±0.2)×10 s快 35 倍。对于这两个相之间的混合相，测量的速率与无序体相中凝胶域的结构一致。
