title: Is the gramicidin a transmembrane channel single-stranded or double-stranded helix? A simple unequivocal determination.
abstract: Thallium ion-induced carbonyl carbon chemical shifts were compared for all of the L-residue-peptide carbonyl carbons of the gramicidin A transmembrane channel. Molecular structures were deduced by using the argument that helically equivalent and equally proximal carbonyls would exhibit essentially equivalent ion-induced chemical shifts. The transmembrane channel was found to be a head-to-head dimer with the structure of a left-handed, single-stranded beta-helix.
authors.forename: D W
authors.initials: DW
authors.lastname: Urry
authors.forename: T L
authors.initials: TL
authors.lastname: Trapane
authors.forename: K U
authors.initials: KU
authors.lastname: Prasad