title: Equilibrium binding constants for the group I metal cations with gramicidin-A determined by competition studies and T1+-205 nuclear magnetic resonance spectroscopy.
abstract: The equilibrium binding constants of the Group I metal cations with gramicidin A in aqueous dispersions of lyso-PC have been determined using a combination of competitive binding with the T1+ ion and T1-205 NMR spectroscopy. The values of the binding constants at 34 degrees C are Li (32.2 M-1), Na (36.9 M-1), K (52.6 M-1), Rb (55.9 M-1), and Cs (54.0 M-1). The equilibrium binding constant for the T1+ ion at this temperature is 582 M-1. The relationships between the binding constants, the free energy of the binding process, and the cation selectivity of the gramicidin A channel are discussed.
mesh_terms: D002414:Cations, Monovalent; D006096:Gramicidin; D007700:Kinetics; D008244:Lysophosphatidylcholines; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008954:Models, Biological; D008958:Models, Molecular; D011485:Protein Binding; D013793:Thallium
chemical_list: D002414:Cations, Monovalent; D008244:Lysophosphatidylcholines; D006096:Gramicidin; D013793:Thallium