Hydrogen bond analysis for all eight possible protonation setups concerning E80 (H/−), E412 (H/−), and E417 (H/−). All hydrogen bonds formed between donors and acceptors of the side chains of E80, Q277, E412, and E417 are considered, as well as hydrogen bonds in which the backbone oxygen atom of L414 participates as an acceptor. Hydrogen bond stability, following the color scale, is illustrated for each chain in each of three runs (100 ns in duration). Hydrogen bonds in which Q277 participates as a donor are highlighted by black boxes.