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Matrix-assisted laser desorption/ionization by infrared laser (IR-MALDI) is one of the most promising techniques for selective soft ionization of biomolecules, as peptides and proteins have very characteristic absorption peaks in infrared light. The dependence of the IR absorption spectra on the state of the matrix molecules, such as crystal solid structure and gas phase, is studied by Masanori Tachikawa and coworkers on page 125 using density functional theory and second-order Møller-Plesset perturbation theory. This leads the way to possible improvements of the sensitivity of IR-MALDI, currently the main limit to its wider application.