Evidence for radical anion formation during liquid secondary ion mass spectrometry analysis of oligonucleotides and synthetic oligomeric analogs: a deconvolution algorithm for molecular ion region clusters

• Published in: Analytical chemistry (Washington) Vol. 61; no. 19; pp. 2154 - 2160
• Main Authors: Laramee, J. A, Arbogast, B, Deinzer, M. L
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.10.1989
• Subjects: Algorithms; Anions; Biological and medical sciences; Carbamates - analysis; Electrons; Free Radicals; Fundamental and applied biological sciences. Psychology; Mass Spectrometry - methods; Molecular biophysics; Molecular Structure; Morpholines - analysis; Oligonucleotides - analysis; Spectroscopy : techniques and spectras; Molecular orbital; Deconvolution; Synthetic product; Electron affinity; Radical anion; Oligonucleotide; Mass spectrometry
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac00194a008

It is shown that one-electron reduction is a common process that occurs in negative ion liquid secondary ion mass spectrometry (LSIMS) of oligonucleotides and synthetic oligonucleosides and that this process is in competition with proton loss. Deconvolution of the molecular anion cluster reveals contributions from (M-2H).-, (M-H)-, M.-, and (M + H)-. A model based on these ionic species gives excellent agreement with the experimental data. A correlation between the concentration of species arising via one-electron reduction [M.- and (M + H)-] and the electron affinity of the matrix has been demonstrated. The relative intensity of M.- is mass-dependent; this is rationalized on the basis of base-stacking. Base sequence ion formation is theorized to arise from M.- radical anion among other possible pathways.