Ollmann M, Schwarzmann G, Sandhoff K, Galla H J
Institut für Biochemie, Technische Hochschule Darmstadt, FRG.
Biochemistry. 1987 Sep 8;26(18):5943-52. doi: 10.1021/bi00392a055.
By use of the excimer technique, the formation in aqueous solution of pyrene-labeled ganglioside micelles and their lateral diffusion and distribution in phosphatidylcholine membranes were investigated. For these studies 12-(1-pyrenyl)dodecanoic acid was covalently attached to the ceramide part of lysogangliosides GM1, GM2, GM3, GD1a, and GD1b. The 12-(1-pyrenyl)dodecanoic acid substitute of phosphatidylcholine was used for comparison. All pyrene-labeled gangliosides were present in aqueous solution in a predominantly micellar form down to 2 X 10(-8) M, which is the technical limit of this method. The tendency to aggregate is highest for PyGD1a and PyGD1b. In fluid dipalmitoylphosphatidylcholine bilayers the excimer-to-monomer fluorescence intensity ratio of pyrene-labeled gangliosides PyGM1, PyGM2, PyGM3, PyGD1a, and PyGD1b increases linearly with ganglioside concentration. The calculated diffusion coefficients for gangliosides are comparable to 1.6 X 10(-7) cm2/s, which is the diffusion coefficient of pyrene-labeled phosphatidylcholine [Galla, H.-J., & Hartmann, W. (1980) Chem. Phys. Lipids 27, 199-219]. In comparison to phosphatidylcholine, the diffusion of monosialogangliosides is slightly increased, with that diffusion of disialogangliosides being slightly decreased. Ca2+ ions up to 200 mM do not affect ganglioside diffusion significantly. The shape of the lipid phase transition curves obtained by the excimer technique yields information on the lateral distribution of the tested probe molecules. Pyrene-labeled phosphatidylcholine was taken as reference for a system with complete miscibility but nonideal mixing. 1-Acyl-2-[10-(1-pyrenyl)decanoyl]-sn-glycero-3-phosphocholine (PyPC) is known to be randomly distributed in the gel and in the fluid-crystalline lipid phase of dipalmitoylphosphatidylcholine bilayer membranes. It distributes preferentially into the fluid phase in the phase-transition region. In comparison, PyPC in dimyristoylphosphatidylcholine membranes is an example of a system with nearly ideal mixing [Hresko, R. C., Sugar, J. P., Barenholz, Y., & Thompson, T. E. (1986) Biochemistry 25, 3813-3828]. Phase-transition curves of pyrene-labeled gangliosides exemplify a nearly ideal mixing system with PyGD1a or PyGD1b producing best effects. The monosialogangliosides, however, exhibit less ideality of mixing, the deviation from an ideal mixing behavior increasing with decreasing number of both neutral sugar residues and sialic acid groups. Addition of Ca2+ triggers a tightening of the phosphatidylcholine bilayer and thus induces a change in the lateral distribution of the gangliosides at the phase transition.(ABSTRACT TRUNCATED AT 400 WORDS)
利用准分子技术，研究了芘标记的神经节苷脂胶束在水溶液中的形成及其在磷脂酰胆碱膜中的横向扩散和分布。在这些研究中，12-(1-芘基)十二烷酸共价连接到溶血神经节苷脂GM1、GM2、GM3、GD1a和GD1b的神经酰胺部分。使用12-(1-芘基)十二烷酸取代的磷脂酰胆碱作为对照。所有芘标记的神经节苷脂在水溶液中主要以胶束形式存在，浓度低至2×10(-8)M，这是该方法的技术极限。PyGD1a和PyGD1b的聚集倾向最高。在流体二棕榈酰磷脂酰胆碱双层膜中，芘标记的神经节苷脂PyGM1、PyGM2、PyGM3、PyGD1a和PyGD1b的准分子与单体荧光强度比随神经节苷脂浓度线性增加。计算得到的神经节苷脂扩散系数与1.6×10(-7)cm2/s相当，这是芘标记的磷脂酰胆碱的扩散系数[加拉，H.-J.，&哈特曼，W.(1980)化学物理脂质27，199-219]。与磷脂酰胆碱相比，单唾液酸神经节苷脂的扩散略有增加，而双唾液酸神经节苷脂的扩散略有降低。高达200mM的Ca2+离子对神经节苷脂扩散没有显著影响。通过准分子技术获得的脂质相变曲线形状提供了有关测试探针分子横向分布的信息。芘标记的磷脂酰胆碱被用作具有完全混溶性但非理想混合的系统的参考。已知1-酰基-2-[10-(1-芘基)癸酰基]-sn-甘油-3-磷酸胆碱(PyPC)随机分布在二棕榈酰磷脂酰胆碱双层膜中的凝胶相和液晶脂质相中。它在相变区域优先分布到流体相中。相比之下，二肉豆蔻酰磷脂酰胆碱膜中的PyPC是一个几乎理想混合系统的例子[赫雷斯科，R.C.，苏格，J.P.，巴伦霍尔兹，Y.，&汤普森，T.E.(1986)生物化学25，3813-3828]。芘标记的神经节苷脂的相变曲线例证了一个几乎理想的混合系统，其中PyGD1a或PyGD1b产生最佳效果。然而，单唾液酸神经节苷脂表现出较少的混合理想性，随着中性糖残基和唾液酸基团数量的减少，与理想混合行为的偏差增加。添加Ca2+会导致磷脂酰胆碱双层收紧，从而在相变时引起神经节苷脂横向分布的变化。(摘要截断于400字)
