Chain-Length-Dependent Autocatalytic Hydrolysis of Fatty Acid Anhydrides in Polyethylene Glycol
Chain-Length-Dependent Autocatalytic Hydrolysis of Fatty Acid Anhydrides in Polyethylene Glycol
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DOI：
10.1021/jp4125233
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发表时间：
2014-03-27
影响因子：
3.3
通讯作者：
Deng, Shao-Ping
中科院分区：
文献类型：
--
作者：
Cao, Cao;Wang, Qing-Biao;Deng, Shao-Ping
由自发形成的囊泡诱导的脂肪酸酐的自催化水解已经被研究了多年。然而，在稀释溶液中形成的囊泡的自催化反应是否也适用于大分子拥挤的条件仍然未知。本研究的目的是表征脂肪酸酐在拥挤介质中的水解行为和囊泡的形成。采用聚乙二醇（PEG）和葡聚糖等惰性大分子拥挤剂研究了外部拥挤对不同疏水链长度脂肪酸酐自催化水解的影响。在拥挤的严格条件下，辛酸酐，壬酸酐和癸酸酐的水解速率被发现降低，但月桂酸酐和油酸酐的速率增加。这些结果表明，拥挤剂对脂肪酸酐水解的影响是链长依赖性的。拥挤条件下水解脂肪酸酐形成的囊泡的尺寸和多分散性表征表明，在较低浓度的PEG下，长链脂肪酸更容易形成单分散囊泡。在PEG存在下的离子化脂肪酸的临界聚集浓度的测量表明，拥挤媒体促进囊泡形成从长链脂肪酸，但抑制那些从脂肪酸具有较少的碳原子。进一步研究离子化脂肪酸在拥挤剂中的扩散性质表明，PEG可能会为长链脂肪酸酐创造更多的疏水区域，从而促进水相中未反应的酸酐溶解在形成的囊泡中。本研究为理解伴随自生聚集体的自催化反应和脂肪酸在拥挤介质中的行为提供了信息。
Autocatalytic hydrolysis of fatty acid anhydrides induced by the spontaneously formed vesicles has been studied for years. However, whether the reaction autocatalyzed by vesicles formed in diluted solutions applies also to macromolecular crowded conditions remains unknown. The aim of this study is to characterize hydrolysis behavior of fatty acid anhydrides and formation of vesicles in crowded media. Inert macromolecular crowding agents such as polyethylene glycol (PEG) and Dextran were used to probe the impact of external crowding on the autocatalytic hydrolysis of fatty acid anhydrides with varied hydrophobic chain length. Under stringent conditions of crowding, hydrolysis rates of octanoic anhydride, nonanoic anhydride, and decanoic anhydride were found to decrease, but the rates of lauric anhydride and oleic anhydride increased. These results suggest that the effect of the crowding agent on the hydrolysis of fatty acid anhydrides was chain-length-dependent. Characterization of the size and polydispersity of vesicles formed from hydrolyzed fatty acid anhydrides in crowding revealed that long-chain fatty acids formed monodisperse vesicles easier at lower concentrations of PEG. Measurement of the critical aggregation concentration of ionized fatty acid in the presence of PEG showed that crowding media promoted vesicle formation from long-chain fatty acids but inhibited those from fatty acids with fewer carbon atoms. Further investigation of the diffusion property of ionized fatty acids in crowding agents suggested that PEG might create more hydrophobic areas for long-chain fatty acids anhydrides, which subsequently promoted the unreacted anhydride in the aqueous phase to be solubilized in the formed vesicles. This research provides information for understanding the autocatalytic reaction accompanied by self-producing aggregates and the behavior of fatty acids in crowding media.