Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) differentially influence lipid oxidation, signal transduction, fluidity, and cholesterol domain formation, potentially due in part to distinct membrane interactions. We used small angle X-ray diffraction to evaluate the EPA and DHA effects on membrane structure. Membrane vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and cholesterol (C) (0.3C:POPC mole ratio) were prepared and treated with vehicle, EPA, or DHA (1:10 mol ratio to POPC). Electron density profiles generated from the diffraction data showed that EPA increased membrane hydrocarbon core electron density over a broad area, up to ± 20 Å from the membrane center, indicating an energetically favorable extended orientation for EPA likely stabilized by van der Waals interactions. By contrast, DHA increased electron density in the phospholipid head group region starting at ± 12 Å from the membrane center, presumably due to DHA-surface interactions, with coincident reduction in electron density in the membrane hydrocarbon core centered ± 7–9 Å from the membrane center. The membrane width (d-space) decreased by 5 Å in the presence of vehicle as the temperature increased from 10 °C to 30 °C due to increased acyl chain trans-gauche isomerizations, which was unaffected by addition of EPA or DHA. The influence of DHA on membrane structure was modulated by temperature changes while the interactions of EPA were unaffected. The contrasting EPA and DHA effects on membrane structure indicate distinct molecular locations and orientations that may contribute to observed differences in biological activity.

二十碳五烯酸（EPA）和二十二碳六烯酸（DHA）差异地影响脂质氧化，信号转导，流动性和胆固醇结构域的形成，这可能部分是由于独特的膜相互作用所致。我们使用小角度X射线衍射来评估EPA和DHA对膜结构的影响。由1-棕榈酰基-2-油酰基-sn组成的膜囊泡制备了3-甘油-3-磷酸胆碱（POPC）和胆固醇（C）（0.3C：POPC摩尔比），并用溶媒，EPA或DHA（与POPC的摩尔比为1:10）处理。由衍射数据生成的电子密度分布图表明，EPA在较膜中心最多±20Å的较宽区域内提高了膜烃核的电子密度，这表明范德华相互作用可能稳定了EPA在能量上有利的扩展取向。相比之下，DHA增加了从膜中心起±12Å处的磷脂头基区域的电子密度，这可能是由于DHA表面相互作用所致，同时膜碳氢化合物核中的电子密度也相应地降低了7 -9Å（从膜中心开始）。膜中心。膜宽（d的存在下，由于存在的酰基链反式-gaoche异构化增加，温度从10°C升高到30°C，因此在载剂存在下降低了5Å，而这不受添加EPA或DHA的影响。DHA对膜结构的影响受温度变化的影响，而EPA的相互作用不受影响。EPA和DHA对膜结构的影响相反，表明不同的分子位置和方向可能有助于观察到的生物活性差异。