HPLC Characterization of the Gramicidin A Dimer-Monomer Conformational Equilibrium in Ethanol and Study of the Effect of Calcium Ion

Abstract
The usefulness of size-exclusion high-performance liquid chromatography for the study of gramicidin A (GA) dimer-monomer conformational equilibrium in polar organic solvents is demonstrated for the first time. The monome-rization process of GA in ethanol has been analyzed using an Ultrastyragel 1000 Å column isocratically equilibrated with tetrahydrofuran, which has allowed the determination of kinetic and thermodynamic constants. Furthermore, the kinetics of interaction of Ca2+ with GA in ethanol has been followed using this methodology, and the binding mechanism has been investigated in terms of the poly-peptide dimer-monomer conformational equilibrium.

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