(color online) Average insertion depths of individual residues into the membranes (black line) and the numbers of hydrogen bonds formed between residues and the lipid membranes (blue line). Hydrogen bonds are counted between a donor atom (D) and an acceptor atom (A) provided that the distance (D–A) is less than 3.5 Å and the angle (D–H–A) is less than 30° Panels (a)–(c) are for the N-terminal helices of Epsin, Sar1p, and Arf1, respectively.