Ponnumallayan Prasanna, Fee Conan J
Department of Chemical and Process Engineering and the Biomolecular Interaction Centre, University of Canterbury , Private Bag 4800, Christchurch, New Zealand 8041.
Langmuir. 2014 Dec 2;30(47):14250-6. doi: 10.1021/la502360k. Epub 2014 Nov 17.
The use of external triggers to manipulate the secondary structure of self-assembling peptides conjugated to flexible synthetic polymers is a challenging problem, particularly in terms of reversibility. Here, we demonstrate, for the first time, sustained rapid and reversible, pH-regulated self-assembly of the peptide ELELELELELF (EL-5F) and its conjugates with 2 and 5 kDa poly(ethylene glycol) (EL-5F-PEG-2K and EL-5F-PEG-5K). Circular dichroism indicated the formation of β-sheet structures at pH < 5.9, 5.8, and 5.4 and disassembly to random coils above those pH values for EL-5F, EL-5F-PEG-2K, and EL-5F-PEG-5K, respectively. β-sheets were confirmed by the thioflavin T assay, while transmission electron microscopy revealed the existence of extended fibrillar structures below the above pH values. pH-induced secondary structure conversion was reproducible for over 15 cycles, even at salt concentrations of up to 200 mM NaCl, and was quantitatively related to the pH. Self-supporting hydrogelation after self-assembly was observed at concentrations as low as 0.2 wt %, which is 15-fold lower than previously reported concentrations. This simple approach to mediate reversible self-assembly of EL-5F-PEG bioconjugates is expected to offer novel functionality relevant to drug delivery and bioseparation systems.
利用外部触发因素来操控与柔性合成聚合物共轭的自组装肽的二级结构是一个具有挑战性的问题，尤其是在可逆性方面。在此，我们首次展示了肽ELELELELELF（EL-5F）及其与2 kDa和5 kDa聚乙二醇的共轭物（EL-5F-PEG-2K和EL-5F-PEG-5K）持续快速且可逆的pH调节自组装过程。圆二色性表明，对于EL-5F、EL-5F-PEG-2K和EL-5F-PEG-5K，分别在pH < 5.9、5.8和5.4时形成β-折叠结构，而在高于这些pH值时解聚为无规卷曲。硫黄素T检测证实了β-折叠的存在，同时透射电子显微镜揭示了在上述pH值以下存在延伸的纤维状结构。即使在高达200 mM NaCl的盐浓度下，pH诱导的二级结构转变在超过15个循环中都是可重复的，并且与pH定量相关。在低至0.2 wt%的浓度下观察到自组装后形成自支撑水凝胶，这比先前报道的浓度低15倍。这种介导EL-5F-PEG生物共轭物可逆自组装的简单方法有望为药物递送和生物分离系统提供新的功能。
