Insertion of flexible, 4-aminobutyroyl spacers in between the cholate repeat units had been found previously to enhance the folding of cholate oligomers in homogeneous solution (Zhao, Y. J. Org. Chem. 2009, 74, 834−843). The opposite effect was observed when the oligomers were solubilized in aqueous solutions of sodium dodecyl sulfate (SDS). The spacers enabled formation of tight aggregates of the oligocholates in SDS solutions when the surfactant was below its critical micelle concentration (CMC). Above the CMC, SDS micelles formed and dissociated the oligocholate aggregates. The parent oligocholates (without spacers in between the repeat units) also aggregated when they were too short to fold (e.g., dimer). The longer tetramer and hexamer preferred to fold, as their rigid, awkwardly shaped backbones prevented tight packing needed in the formation of stable aggregates. Folding was favored both below and above the CMC of SDS and was enhanced by an increase in the chain length.
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机译：先前已经发现在胆酸盐重复单元之间插入柔性的4-氨基丁酰基间隔基可以增强胆酸盐低聚物在均相溶液中的折叠（Zhao，Y. J. Org。Chem。2009，74，834-843）。当将低聚物溶解在十二烷基硫酸钠（SDS）的水溶液中时，观察到相反的效果。当表面活性剂低于其临界胶束浓度（CMC）时，间隔物可在SDS溶液中形成致密的寡酚盐聚集体。在CMC上方，SDS胶束形成并解离了寡聚胆酸盐的聚集体。当它们太短而不能折叠（例如，二聚体）时，母体寡聚胆甾醇（在重复单元之间没有间隔）。较长的四聚体和六聚体最好折叠，因为它们的刚性，笨拙的骨架阻止了形成稳定聚集体所需的紧密堆积。在SDS的CMC之下和之上均有利于折叠，并通过增加链长来增强折叠性。
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