Effects of Electric Filed on β-sheet Propensity Self-Assembled Amphiphile Peptides

Abstract

This study investigated the roles of amino acid sequence and type of anions on short peptide amphiphiles by applying external electric field. We designed two synthetic peptides of FFKKFF and KFFFFK with amino acid sequence and charge distribution that varied systematically. Next, the effects of aqueous milieu to the self-assembled structure stability was investigated through the addition of anion (I- or ClO4-). Growth and structural transition of the self-assembled structures was followed by using circular dichroism (CD) and scanning electron microscope (SEM) for 48 hours on removal of DC electric field. Diverse micrometre-sized self-assembled structures can be obtained depending on different anion presence in the solution. Our results showed that all the peptides favoured a needle-like structure in solutions containing ClO4-, which mainly consists of α-helical and β-sheet conformations with or without the electric field. It was found that the application of electric field stimulate the formation of a higher extend of end-to-end integration or sideways association. The absence of electric field facilitated the formation of a stable and organised network of interwoven fibrillary structure at 48th hour in solutions containing I-. Interestingly, fine needle-like structure was observed when electric field was applied to the same solutions. Our findings suggested that electric field favours the change of the peptides from β-sheet to a mixture of α-helical and β-sheet conformations in solutions containing I-. Removing the electric field did not reinstate the original conformation