Nonresonant MALDI of oligonucleotides: Mechanism of ion desorption

Oligonucleotide ions have been detected using matrix-assisted laser desorpt ion/ionization (MALDI) under nonresonant laser irradiation of the sample. W hen mass resolution was not limited by adduct attachment to the analyte ion s, the nonresonant MALDI spectra demonstrated better resolution than the sp ectra acquired with resonant ultraviolet irradiation. We found that prepara tion of thin-him samples on absorbing substrate surfaces was critical for t he success of NR-MALDI. The possible acoustic mechanisms of ion formation a nd desorption are discussed.