Agafonov Alexey V, Gritsenko Elena N, Shlyapnikova Elena A, Kharakoz Dmitry P, Belosludtseva Natalia V, Lezhnev Enrik I, Saris Nils-Erik L, Mironova Galina D
Laboratory of Mitochondrial Transport, Institute of Theoretical and Experimental Biophysics RAS, Institutskaya str. 3, Pushchino, Moscow Region 142290, Russia.
J Membr Biol. 2007 Jan;215(1):57-68. doi: 10.1007/s00232-007-9005-4. Epub 2007 Apr 19.
A Ca(2+)-induced phase separation of palmitic acid (PA) in the membrane of azolectin unilamellar liposomes has been demonstrated with the fluorescent membrane probe nonyl acridine orange (NAO). It has been shown that NAO, whose fluorescence in liposomal membranes is quenched in a concentration-dependent way, can be used to monitor changes in the volume of lipid phase. The incorporation of PA into NAO-labeled liposomes increased fluorescence corresponding to the expansion of membrane. After subsequent addition of Ca(2+), fluorescence decreased, which indicated separation of PA/Ca(2+) complexes into distinct membrane domains. The Ca(2+)-induced phase separation of PA was further studied in relation to membrane permeabilization caused by Ca(2+) in the PA-containing liposomes. A supposition was made that the mechanism of PA/Ca(2+)-induced membrane permeabilization relates to the initial stage of Ca(2+)-induced phase separation of PA and can be considered as formation of fast-tightening lipid pores due to chemotropic phase transition in the lipid bilayer.
用荧光膜探针壬基吖啶橙（NAO）已证明在偶氮卵磷脂单层脂质体膜中棕榈酸（PA）存在Ca(2+)诱导的相分离。已表明，在脂质体膜中其荧光以浓度依赖性方式猝灭的NAO可用于监测脂质相体积的变化。将PA掺入NAO标记的脂质体中会增加与膜扩张相对应的荧光。随后加入Ca(2+)后，荧光降低，这表明PA/Ca(2+)复合物分离成不同的膜结构域。进一步研究了PA的Ca(2+)诱导相分离与含PA脂质体中Ca(2+)引起的膜通透性之间的关系。有人推测，PA/Ca(2+)诱导的膜通透性机制与PA的Ca(2+)诱导相分离的初始阶段有关，并且可被认为是由于脂质双层中的化学趋向性相变形成了快速收紧的脂质孔。
