title: Comparison of intensities between doubly charged ions [M + 2H]2+ and singly charged ions [M + H]+ of gramicidin S by electrospray mass spectrometry.
abstract: The reason why the intensity of doubly charged ions [M + 2H]2+ of gramicidin S is higher than that of singly charged ions [M + H]+ in electrospray is investigated by ion evaporation theory. As a result of comparison between the total free energies of extracting [M + 2H]2+ and [M + H]+ from a charged droplet to infinity, it is found that the total free energy of [M + 2H]2+ is estimated to be lower than that of [M + H]+. This clearly supports the experimental result. In addition, the importance of the electrostatic contribution in electrospray is demonstrated by showing the result that the total free energy of [M + 2H]2+ without electrostatic contribution is higher than that of [M + H]+.
authors.affiliation: Central Research Laboratory, Hitachi Ltd., Tokyo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Sakairi
authors.forename: A L
authors.initials: AL
authors.lastname: Yergey
mesh_terms: D006096:Gramicidin / Q000737:chemistry*; D013058:Mass Spectrometry
chemical_list: D006096:Gramicidin