A) Left panel: overlay of the models resulting from the introduction of Arg and Asp into the 2M5N zipper structure, with the identifier indicated for each strand. Strands E and F are highlighted in red. Right panel: the same structure turned 90° about both the x- and y-axes. Arrows in (a) indicate the capacities of Arg and Asp to distance their charged moieties. (b) shows an example of planar Arg stacking. 