The gramicidin A channel: comparison of the energy profiles of Na⁺, K⁺ and Cs⁺. Influence of the flexibility of the ethanolamine end chain on the profiles

The energy profiles for single occupancy by Cs⁺ and Na⁺ in the gramicidin A channel assumed to be in a head-to-head β^6.3_3.3 helical dimeric structure, were computed: (A) allowing complete conformational freedom to the ethanolamine end, (B) constraining it to stay in its intrinsically preferred conformation. Whatever the constraint, both the entrance barrier and the central barrier appear in the order Cs⁺< K⁺< Na⁺. Introducing the flexibility of the tail modifies appreciably the profiles and the location of the extrema along it. Energy profile Gramicidin A Ethanolamine end Caesium Potassium Sodium Energy barrier Theoretical computation.