Reversible and rapid pH-regulated self-assembly of a poly(ethylene glycol)-peptide bioconjugate.
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.
Department of Chemical and Process Engineering and the Biomolecular Interaction Centre, University of Canterbury , Private Bag 4800, Christchurch, New Zealand 8041.
Prasanna
P
Ponnumallayan
Conan J
CJ
Fee
D006863:Hydrogen-Ion Concentration; D010455:Peptides / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D017433:Protein Structure, Secondary
D010455:Peptides; D011108:Polymers; D011092:Polyethylene Glycols