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Thermochemistry of Multiply Charged Melittin in the Gas Phase Determined by the Modified Kinetic Method
Author(s) -
Kaltashov Igor A.,
Fenselau Catherine
Publication year - 1996
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/(sici)1097-0231(199605)10:7<857::aid-rcm577>3.0.co;2-m
Subject(s) - chemistry , melittin , kinetic energy , dissociation (chemistry) , protonation , metastability , thermochemistry , ion , mass spectrometry , gas phase , activation energy , analytical chemistry (journal) , chromatography , organic chemistry , peptide , biochemistry , physics , quantum mechanics
The modified kinetic method was expanded to measuring gas‐phase basicities of biopolymers carrying two or more charges. Relative rates of the unimolecular dissociation of metastable multiply charged proton‐bound dimers formed by melittin and reference bases provided the values of ‘apparent’ gas‐phase basicities. These numbers are offset by the height of the reverse activation energy barrier due to Coulombic repulsion in charge separation processes, which have been measured experimentally using mass‐analyzed ion kinetic energy spectrometry. The gas‐phase basicity of doubly protonated melittin was determined to be 200.0±3.4 kcal/mol, while the basicity of the same polypeptide carrying three protons was determined to be 179.1±3.6 kcal/mol.