Supramolecular structure of a helical ribbon peptide self-assembly

We have studied the supramolecular structure of nanometer scale helical ribbons observed in the self-assembly of beta-sheets forming peptide KFE8 (amino acid sequence: FKFEFKFE). By running molecular dynamics simulations on a wide range of possible combinations of single and double layer beta-sheet ribbons, we identified the most stable structure. The effect of solution pH was incorporated by scaling the charge on sidechains based on electrostatic double layer theory. Our results suggest that the helical ribbon is comprised of a double beta-sheet having multiple local energy minima at different pitch values. Electrostatic interactions between charged sidechains are found to be crucial in determining the curvature and elasticity of the helix, which suggests that the helical shape depends on the solution properties. Our approach has general applicability to studying helices made of beta-sheet forming peptides with various amino acid sequences.