Ali S, Brockman H L, Brown R E
Hormel Institute, University of Minnesota, Austin 55912.
Biochemistry. 1991 Nov 26;30(47):11198-205. doi: 10.1021/bi00111a002.
The Langmuir film balance technique has been used to define the surface structure and determine the mixing behavior of galactosylceramide (GalCer) and phosphatidylcholines in surface phases. To determine the effect of unsaturation on surface behavior, chain-pure GalCer species containing either oleoyl (18:1 delta 9), eicosenoyl (20:1 delta 11), or eicosadienoyl (20:2 delta 11,14) fatty acyl chains were synthesized. Using bovine brain GalCer as a reference, surface pressure versus molecular area (phi-A) isotherms of the pure lipids were measured and analyzed by determining their compressibilities and by using an equation of state for lipid monolayers. This information, when coupled with surface potential versus molecular area (delta V-A) analyses, provides insights into GalCer surface structure in terms of molecular packing and orientation. Lipid mixing behavior was determined by classical approaches which involve analyzing the average molecular area, the average surface dipole moment, and surface pressure as a function of film composition. The results indicate that, in contrast to the complex mixing behavior displayed by bovine brain GalCer and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), chain-pure GalCer species containing either oleoyl, eicosenoyl, or eicosadienoyl fatty acyl chains are miscible with POPC over the entire composition range. Moreover, increasing amounts of GalCer containing eicosenoyl acyl chains systematically elevate dipalmitoylphosphatidylcholine's (DPPC) liquid-expanded-to-liquid-condensed transition pressure. Such behavior is consistent with GalCer being miscible with the liquid-expanded phase of DPPC. Thus, fatty acyl unsaturation is a critical parameter governing the mixing behavior of GalCer with phosphatidylcholine.
朗缪尔膜天平技术已被用于定义表面结构，并确定半乳糖神经酰胺（GalCer）和磷脂酰胆碱在表面相中的混合行为。为了确定不饱和度对表面行为的影响，合成了含有油酰基（18:1 Δ9）、二十碳烯酰基（20:1 Δ11）或二十碳二烯酰基（20:2 Δ11,14）脂肪酰链的链纯GalCer物种。以牛脑GalCer为参考，通过测定纯脂质的压缩性并使用脂质单层的状态方程，测量并分析了纯脂质的表面压力与分子面积（φ-A）等温线。这些信息与表面电势与分子面积（ΔV-A）分析相结合，从分子堆积和取向方面提供了对GalCer表面结构的见解。脂质混合行为通过经典方法确定，该方法涉及分析平均分子面积、平均表面偶极矩以及作为膜组成函数的表面压力。结果表明，与牛脑GalCer和1-棕榈酰-2-油酰-sn-甘油-3-磷酸胆碱（POPC）表现出 的复杂混合行为相反，含有油酰基、二十碳烯酰基或二十碳二烯酰基脂肪酰链的链纯GalCer物种在整个组成范围内都能与POPC互溶。此外，含有二十碳烯酰基酰链的GalCer含量增加会系统性地提高二棕榈酰磷脂酰胆碱（DPPC）的液-扩到液-凝转变压力。这种行为与GalCer能与DPPC的液-扩相互溶一致。因此，脂肪酰不饱和度是控制GalCer与磷脂酰胆碱混合行为的关键参数。
