The Role of Esterification on Detection of Protonated and Deprotonated Peptide Ions in Matrix Assisted Laser Desorption/Ionization (MALDI) Mass Spectrometry (MS)

• Published in: Journal of the American Society for Mass Spectrometry Vol. 16; no. 8; pp. 1269 - 1274
• Main Authors: Lecchi, Paolo, Olson, Matthew, Brancia, Francesco L.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.08.2005; Elsevier Science; Springer Nature B.V
• Subjects: Alcohols; Aliphatic compounds; Amino Acid Sequence; Aminoacids, peptides. Hormones. Neuropeptides; Analytical, structural and metabolic biochemistry; Binary mixtures; Biological and medical sciences; Chemistry; Desorption; Esterification; Esters; Esters - analysis; Esters - chemistry; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Hydrophobic and Hydrophilic Interactions; Ionization; Ions; Mass spectrometry; Molecular Sequence Data; Organic chemistry; Peptides; Peptides - analysis; Peptides - chemistry; Polarity; Proteins; Protonation; Protons; Reactivity and mechanisms; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization - methods; Protonated form; Peptides; Time of flight method; Matrix effect; Matrix assisted laser desorption ionization; Derivatization; Detection; Mass spectrometry; Esterification; Deprotonation
• ISSN: 1044-0305; 1879-1123
• DOI: 10.1016/j.jasms.2005.03.019

Esterification was used to investigate how introduction of aliphatic chains within the peptide structure affects the MALDI response of ions analyzed in both polarity regimes. In binary mixtures containing equimolar amounts of a peptide with its correspondent alkyl ester, derivatization of the carboxylic groups has the tendency to increase MALDI detection of the modified protonated peptide ions. This positive effect on ion yield is more pronounced when longer alcohols are employed. In negative mode, the situation is antithetic and esterification produces a deleterious effect on the ion yield of the corresponding deprotonated species. From the data reported here we postulate that modifications of the acidic character of peptides prevent formation of anionic species under MALDI analysis. Furthermore, suppression of the formation pathway for anions alters the overall number of molecules which can undergo protonation. This results in an increased ion yield for the protonated esters.