(color online) (a) Configurations and (b) corresponding helical wheel representations of the amphiphilic helices of Epsin, Sar1p, and Arf1. Color coding for residues: yellow for hydrophobic, purple for serine and threonine, blue for basic, red for acidic, pink for asparagine and glutamine, grey for alanine and glycine, green for proline, and light blue for histidine. The arrow in helical wheels corresponds to the hydrophobic moment.