FIGURE 6.

Dipole-dipole interactions and hydrogen bonding in the simulated ceramide channels. Snapshots of the 4_L14_C (A) and 6_L14_C (B) C₁₆ simulations in the membrane show that in the stationary phase approximately one-half of the columns preserve the antiparallel orientation of column dipoles arising from the H-bonded amide groups. The original regular hydrogen-bonding pattern (C) randomizes quickly, and on average, in the 6_L14_C C₁₆ simulation approximately one-third of the bonds are dynamically maintained (D). A new pattern of hydroxyl bonding often appears, linking both layers and columns. Water (green) participates in the interceramide hydrogen bonding, acting as a bridge, and partially compensating for the lost bonds. Amide-amide and double-bond–double-bond contact interfaces between the neighboring columns are marked by the double arrows a-a and d-d, respectively.