@article{oai:repository.lib.tottori-u.ac.jp:02001319,
 author = {Watanabe,Hirofumi and 花島,慎弥 and Hanashima,Shinya and Yano,Yo and Yasuda,Tomokazu and Murata,Michio},
 issue = {43},
 journal = {Langmuir},
 month = {Apr},
 note = {Although lateral and interleaflet lipid-lipid interactions in cell membranes play roles in maintaining asymmetric lipid bilayers, the molecular basis of these interactions is largely unknown. Here we established a method to determine the distribution ratio of phospholipids between the outer and inner leaflets of asymmetric large unilamellar vesicles (aLUVs). The trimethylammonium group, (CH3)3N+, in the choline headgroup of N-palmitoyl-sphingomyelin (PSM) and 1,2-dioleoyl-sn-glycero-3-phosphatidylcholine (DOPC) gave rise to a relatively sharp signal in magic angle spinning solid-state 1H NMR (MAS-ss-1H NMR). PSM and DOPC have the same headgroup structure, but one phospholipid was selectively observed by deuterating the trimethylammonium group of the other phospholipid. The addition of Pr3+ to the medium surrounding aLUVs selectively shifted the chemical shift of the (CH3)3N+ group in the outer leaflet from that in the inner leaflet, which allows the estimation of the interleaflet distribution ratio of unlabeled lipid in aLUVs. Using this method, we evaluated the translocation of PSM and DOPC between the outer and inner leaflets of the cholesterol-containing aLUVs, with PSM and DOPC mostly distributed in the outer and inner leaflets, respectively, immediately upon aLUV preparation, and flip and flop rates of approximately 2.7 and 6.4 ×10-6 s-1, respectively. During the passive symmetrization of the aLUVs, the lipid translocation rate was decreased due to changes in the membrane order, probably through the formation of the registered liquid-ordered domains. Comparison of the result with that of symmetric LUVs revealed that lipid asymmetry may not significantly affect the lipid translocation rates while lateral lipid-lipid interaction may be a dominant factor in lipid translocation under these conditions. These findings highlight the importance of considering the effects of lateral lipid interactions within the same leaflet on lipid flip-flop rates when evaluating the asymmetry of phospholipids in the cell membrane.},
 pages = {15189--15199},
 title = {Passive Translocation of Phospholipids in Asymmetric Model Membranes: Solid-State 1H NMR Characterization of Flip-Flop Kinetics Using Deuterated Sphingomyelin and Phosphatidylcholine},
 volume = {39},
 year = {2023},
 yomi = {ハナシマ,シンヤ}
}