The unique attributes of very-long-chain polyunsaturated fatty acids (VLC-PUFAs), their long carbon chains (n > 24) and high degree of unsaturation, impart unique chemical and physical properties to this class of fatty acids. The changes imparted by VLC-PUFA 32:6 n-3 on lipid packing and the compression moduli of model membranes were evaluated from π-A isotherms of VLC-PUFA in 1,2-distearoyl-sn-3-glycero-phosphocholine (DSPC) lipid monolayers. To compare the attractive or repulsive forces between VLC-PUFA and DSPC lipid monolayers, the measured mean molecular areas (MMAs) were compared with the calculated MMAs of an ideal mixture of VLC-PUFA and DSPC. The presence of 0.1, 1, and 10 mol % VLC-PUFA shifted the π-A isotherm to higher MMAs of the lipids comprising the membrane and the observed positive deviations from ideal behavior of the mixed VLC-PUFA:DSPC monolayers correspond to repulsive forces between VLC-PUFAs and DSPC. The MMA of the VLC-PUFA component was estimated using the measured MMAs of DSPC of 47.1 ± 0.7 Å²/molecule, to be 15,000, 1100, and 91 Å²/molecule at 0.1, 1, and 10 mol % VLC-PUFA:DSPC mixtures, respectively. The large MMAs of VLC-PUFA suggest that the docosahexaenoic acid tail reinserts into the membrane and adopts a nonlinear structure in the membrane, which is most pronounced at 0.1 mol % VLC-PUFA. The presence of 0.1 mol % VLC-PUFA:DSPC also significantly increased the compression modulus of the membrane by 28 mN/m compared with a pure DSPC membrane. The influence of VLC-PUFA on lipid “flip-flop” was investigated by sum-frequency vibrational spectroscopy. The incorporation of 0.1 mol % VLC-PUFA increased the DSPC flip-flop rate fourfold. The fact that VLC-PUFA promotes lipid translocation is noteworthy as retinal membranes require a high influx of retinoids which may be facilitated by lipid flip-flop.

超长链多不饱和脂肪酸 (VLC-PUFA) 的独特属性、长碳链 ( n  > 24) 和高度不饱和度，赋予此类脂肪酸独特的化学和物理性质。根据 VLC-PUFA 在 1,2-二硬脂酰-sn-3-甘油磷酸胆碱 (DSPC) 中的 π-A 等温线评估了 VLC-PUFA 32:6 n-3 对脂质堆积和模型膜压缩模量造成的变化）脂质单层。为了比较 VLC-PUFA 和 DSPC 脂质单层之间的吸引力或排斥力，将测量的平均分子面积 (MMA) 与 VLC-PUFA 和 DSPC 理想混合物的计算 MMA 进行比较。0.1、1 和 10 mol% VLC-PUFA 的存在将 π-A 等温线移动到构成膜的脂质的较高 MMA，并且观察到混合 VLC-PUFA:DSPC 单层的理想行为与排斥力相对应的正偏差VLC-PUFA 和 DSPC 之间。使用测得的 DSPC 的 MMA（47.1 ± 0.7 Å ² /分子）估计 VLC-PUFA 组分的 MMA，在 0.1、1 和 10 mol % VLC-PUFA 时分别为 15,000、1100 和 91 Å ² /分子：分别为 DSPC 混合物。VLC-PUFA 的大 MMA 表明二十二碳六烯酸尾部重新插入膜中并在膜中采用非线性结构，这在 0.1 mol% VLC-PUFA 时最为明显。与纯 DSPC 膜相比，0.1 mol% VLC-PUFA:DSPC 的存在也使膜的压缩模量显着增加了 28 mN/m。通过和频振动光谱研究了 VLC-PUFA 对脂质“触发器”的影响。0.1 mol% VLC-PUFA 的掺入使 DSPC 翻转率提高了四倍。VLC-PUFA 促进脂质易位的事实值得注意，因为视网膜膜需要大量的类视黄醇流入，而脂质翻转可能会促进这种情况。