Chain-Length-Dependent Autocatalytic Hydrolysis of Fatty Acid Anhydrides in Polyethylene Glycol

Abstract

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.

Selective Oxygenation of Cyclohexene by Dioxygen via an Iron(V)-Oxo Complex-Autocatalyzed Reaction

“…Because the rate of reaction is proportional to the concentration of product, the time course of the reaction exhibits an induction period with a sigmoidal curvature, as shown in Figure a . Autocatalysis has been extensively studied because it is central to the propagation of living systems. − …”

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“…Unusual chain-length dependence was involved in the vesiclecatalyzed production of fatty acids during macromolecular crowding. 11 In crowded media, the binding of FAs to phospholipid bilayers also displays an unusual behavior. For instance, macromolecular crowding significantly increases the phase transition temperature of lipid vesicles, indicating that the crowded medium contributes to the heterogeneity of the bilayers and might repair disturbed membranes.…”

Thermodynamics and Structural Evolution during a Reversible Vesicle–Micelle Transition of a Vitamin-Derived Bolaamphiphile Induced by Sodium Cholate

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