Investigating covalent and electrostatic binding interactions via gas-phase ion/ion reactions
Gas-phase ion/ion reactions involve the reaction of two oppositely charged ions within the mass spectrometer. There are two types of reactions that can occur during these rapid gas-phase chemistry reactions, particle transfer (e.g.., proton or electron transfer) and/or covalent bond formations. The area of selective covalent modification based on traditional solution-phase reactions represents a fairly new area of gas-phase chemistry. The work demonstrated in this dissertation involves two gas-phase covalent modifications. The first being the reaction between carbenes generated from the singly deprotonated anion 1-diazo-2-napthol-4-sulfonic acid and primary amines and/or hydroxyl groups. This reaction allows for more sequence information to be generated as well as represents the first gas-phase reaction with hydroxyl moieties. The second reaction involves Schiff base formation of unprotonated primary amines of peptides with the reagent anion 4-formyl-1,3-benzene disulfonic acid. Since the byproduct of a Schiff base reaction is the loss of water, and peptides are known to lose water readily in the gas-phase, there was no definitive signature for the reaction occurring. The aldehydic oxygen of the reagent anion was isotopically labelled with oxygen-18 allowing for two distinct water losses to be observed, thus providing a signature for the covalent modification occurring. Work in this dissertation also focuses on the selective gas-phase removal of alkali metal cations on peptides through ion/ion reactions with weakly coordinating anions. The carborane anion, CHB11Cl11-, was the only anion studied to show preferential removal of all alkali metal cations rather than the removal of protons. This work was expanded to be used on biopharmaceutically relevant polymers. By reacting the entire polymer distribution with the carborane anions, the spectra were able to be simplified to one singly charged, singly adducted distribution for more accurate mass determination
McLuckey, Purdue University.
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