Indole, the aromatic element of tryptophan, as a pi-donor and amphiphilic headgroup

Indole, the aromatic sidechain element of tryptophan, may play many biological roles. It may serve as an anchor or organizing element, a hydrogen bond donor, or a Lewis basic donor in the cation–pi sense to alkali metal or ammonium cations. Organic chemistry has been used to develop model systems that probe these interactions and give experimental data concerning their importance.