3.1. The Instability of the Zwitterionic Radicals of Alanine in the Gas-Phase
The absence of a stable zwitterionic radicals () of Ala has never been reported in the literature to the best of the authors’ knowledge. While this is a completely new result as such, it is not dissimilar to the well-known instability of zwitterionic closed-shell amino acids (and in particular of Ala [46-47]) in the gas phase. Only in solution or crystalline phases or through ion bridges in the gas phase [48] are the zwitterionic forms of amino acid stable enough to be detected experimentally. It appears that radical Ala follows the same pattern of behavior and can only exist as a non-zwitterionic species in the gas-phase.