Multiply-sodiated ions were observed by electrospraying oligoglycines and their N-acetylated and O-amidated derivatives in the presence of sodium hydroxide. These ions have all their hydrogens in the peptide linkages replaced by sodiums; one hydrogen in the C-terminal amide and the hydrogen in the C-terminal carboxylic group are also replaced. The N-terminal amine hydrogens are unreactive. These results are consistent with earlier postulations [Int. J. Mass Spectrom. 192 (1999) 303, J. Am. Soc. Mass Spectrom. 11 (2000) 967], and apparently confirm the gas-phase origin of these ions (formed in the electrospray source and/or the lens region). Collision-induced dissociation of multiply-sodiated oligoglycines showed that the major product ions are C-terminal ions.

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Keywords Gas-phase reactions, Oligoglycines, Sodium substitutions
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Journal International Journal of Mass Spectrometry
Grewal, R.Natasha (R. Natasha), Aribi, H.E. (Houssain El), Smith, J. C, Rodriquez, C.F. (Christopher F), Hopkinson, A.C. (Alan C), & Siu, K.W.Michael (K. W.Michael). (2002). Multiple substitution of protons by sodium ions in sodiated oligoglycines. International Journal of Mass Spectrometry, 219(1), 89–99. doi:10.1016/S1387-3806(02)00561-4