Veiga M P, Arrondo J L, Goñi F M, Alonso A
Grupo Biomembranas (Unidad Asociada al CSIC), Departamento de Bioquímica, Universidad del País Vasco, 48080 Bilbao, Spain.
Biophys J. 1999 Jan;76(1 Pt 1):342-50. doi: 10.1016/S0006-3495(99)77201-2.
The effects of ceramides of natural origin on the gel-fluid and lamellar-inverted hexagonal phase transitions of phospholipids (mainly dielaidoylphosphatidylethanolamine) have been studied by differential scanning calorimetry, with additional support from infrared and 31P nuclear magnetic resonance (NMR) spectroscopy. In the lamellar phase, ceramides do not mix ideally with phospholipids, giving rise to the coexistence of domains that undergo the gel-fluid transition at different temperatures. The combination of differential scanning calorimetry and infrared spectroscopy, together with the use of deuterated lipids, allows the demonstration of independent melting temperatures for phospholipid and ceramide in the mixtures. In the lamellar-hexagonal phase transitions, ceramides (up to 15 mol %) decrease the transition temperature, without significantly modifying the transition enthalpy, thus facilitating the inverted hexagonal phase formation. 31P-NMR indicates the coexistence, within a certain range of temperatures, of lamellar and hexagonal phases, or hexagonal phase precursors. Ceramides from egg or from bovine brain are very similar in their effects on the lamellar-hexagonal transition. They are also comparable to diacylglycerides in this respect, although ceramides are less potent. These results are relevant in the interpretation of certain forms of interfacial enzyme activation and in the regulation and dynamics of the bilayer structure of cell membranes.
通过差示扫描量热法研究了天然来源的神经酰胺对磷脂（主要是二油酰磷脂酰乙醇胺）的凝胶-流体和片层-反相六角相转变的影响，并得到了红外光谱和31P核磁共振（NMR）光谱的额外支持。在片层相中，神经酰胺与磷脂不能理想混合，导致在不同温度下发生凝胶-流体转变的区域共存。差示扫描量热法和红外光谱相结合，以及使用氘代脂质，能够证明混合物中磷脂和神经酰胺的独立熔化温度。在片层-六角相转变中，神经酰胺（高达15摩尔%）降低了转变温度，但没有显著改变转变焓，从而促进了反相六角相的形成。31P-NMR表明在一定温度范围内，片层相和六角相或六角相前体共存。来自鸡蛋或牛脑的神经酰胺对片层-六角转变的影响非常相似。在这方面，它们也与二酰基甘油相当，尽管神经酰胺的作用较弱。这些结果对于解释某些形式的界面酶激活以及细胞膜双层结构的调节和动力学具有重要意义。
