Palestini P, Pitto M, Sonnino S, Omodeo-Salè M F, Masserini M
Department of Medical Chemistry and Biochemistry, Medical School, Milano, Italy.
Chem Phys Lipids. 1995 Aug 25;77(2):253-60. doi: 10.1016/0009-3084(95)02474-w.
The spontaneous transfer between membranes of GM3, a ganglioside present in a vesicular form of aggregation instead of micellar form like the majority of gangliosides in aqueous medium, has been studied. Upon incubation of GM3 in the presence of dipalmitoylphosphatidylcholine (DPPC) large unilamellar vesicles at 50 degrees C, mixed GM3/DPPC vesicles are formed. The maximum amount of GM3 that can be inserted into vesicles is about 8%. The temperature dependence of the kinetics has been followed by the excimer formation technique, using the fluorescent analogue pyrenyldodecanoyl-GM3. The transfer of ganglioside from its vesicles to DPPC vesicles depends on the physicochemical characteristics of both the donor and of the acceptor vesicles and increases with the temperature (k = 0.006 0.012, 0.037 at 30, 41 and 50 degrees C, respectively), with a major break point at 41 degrees C and a minor one at 35 degrees C. These temperatures correspond to the gel- to liquid-crystalline transition of DPPC (Tm = 41.3 degrees C), and to a temperature transition displayed by GM3 ganglioside. Similar experiments performed with erythrocyte ghosts yielded a rate constant of 0.04 at 37 degrees C. For the transfer of ganglioside from DPPC (donor) to DMPC (acceptor) the rate constants were 0 at 15 degrees C (both phospholipids in the gel phase), 0.005 at 37 degrees C (donor in the gel phase, acceptor in the fluid phase) and 0.04 at 50 degrees C (both phospholipids in the fluid phase).(ABSTRACT TRUNCATED AT 250 WORDS)
已对神经节苷脂GM3在膜之间的自发转移进行了研究。GM3以聚集的囊泡形式存在，而非像大多数神经节苷脂在水介质中那样以胶束形式存在。在50℃下，将GM3与二棕榈酰磷脂酰胆碱（DPPC）大单层囊泡一起孵育时，会形成混合的GM3/DPPC囊泡。能够插入囊泡的GM3的最大量约为8%。利用荧光类似物芘十二烷酰-GM3，通过准分子形成技术追踪了动力学的温度依赖性。神经节苷脂从其囊泡向DPPC囊泡的转移取决于供体囊泡和受体囊泡的物理化学特性，并随温度升高而增加（在30℃、41℃和50℃时，k分别为0.006、0.012、0.037），在41℃有一个主要转折点，在35℃有一个次要转折点。这些温度分别对应于DPPC从凝胶态到液晶态的转变（Tm = 41.3℃），以及GM3神经节苷脂显示的温度转变。用红细胞血影进行的类似实验在37℃时得到的速率常数为0.04。对于神经节苷脂从DPPC（供体）向DMPC（受体）的转移，在15℃时速率常数为0（两种磷脂均处于凝胶相），在37℃时为0.005（供体处于凝胶相，受体处于流体相），在50℃时为0.04（两种磷脂均处于流体相）。（摘要截短于250字）
