The influence of four common cryoprotectants (dimethyl sulfoxide, glycerol, ethylene glycol and dimethylformamide) on monolayers of four common phospholipids (DPPC, DOPC, POPC and POPE) have been studied using Langmuir isotherms and monolayer insertion experiments. The cryoprotectant concentrations were chosen to be directly relevant to cryoprotection. We show that DMSO causes an expansion of the DPPC area per lipid (in contrast to previous work at higher concentrations). However, it caused compression for POPC, and had little effect for POPE or DOPC. As most previous studies have involved only DPPC, this highlights the importance of studying different lipid types as these may have a significant effect on the interactions. We show that both ethylene glycol and glycerol cause a small expansion of the monolayer at fixed pressure, implying that they insert into the headgroup regions, regardless of lipid species, and consistent with their ability to penetrate membranes. By contrast, dimethylformamide causes monolayer compression for all lipid species, implying it dehydrates the lipid head groups. Membrane insertion experiments at physiological values of lateral pressure highlight that DPPC is the most difficult lipid to penetrate, implying that the penetrating action of cryoprotectants may only occur for unsaturated phospholipids. Thus, extrapolations of results based solely on the DPPC need to be made with care.

使用Langmuir等温线和单层插入实验研究了四种常用的冷冻保护剂（二甲亚砜，甘油，乙二醇和二甲基甲酰胺）对四种常用磷脂（DPPC，DOPC，POPC和POPE）单层的影响。选择防冻剂浓度与防冻剂直接相关。我们表明，DMSO会导致每个脂质的DPPC面积扩大（与以前在较高浓度下的工作形成对比）。但是，它对POPC造成压缩，而对POPE或DOPC几乎没有影响。由于大多数先前的研究仅涉及DPPC，因此这突出了研究不同脂质类型的重要性，因为它们可能对相互作用产生重大影响。我们显示乙二醇和甘油都会在固定压力下引起单层的小膨胀，这意味着它们无论脂类如何都插入头基区域，并与其渗透膜的能力保持一致。相比之下，二甲基甲酰胺会引起所有脂质种类的单层压缩，这意味着它使脂质头基脱水。在侧向压力的生理值下进行的膜插入实验表明，DPPC是最难渗透的脂质，这意味着冷冻保护剂的渗透作用仅可能发生于不饱和磷脂。因此，必须谨慎地仅基于DPPC推断结果。在侧向压力的生理值下进行的膜插入实验表明，DPPC是最难渗透的脂质，这意味着冷冻保护剂的渗透作用仅可能发生于不饱和磷脂。因此，必须谨慎地仅基于DPPC推断结果。在侧向压力的生理值下进行的膜插入实验表明，DPPC是最难渗透的脂质，这意味着冷冻保护剂的渗透作用仅可能发生于不饱和磷脂。因此，必须谨慎地仅基于DPPC推断结果。