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Theoretical analysis of correlation between ionization threshold fluence in IR‐MALDI and IR absorption spectrum of matrix molecules |
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| Authors: | Makoto Hatakeyama Takako Mashiko Hisanao Hazama Kunio Awazu Masanori Tachikawa |
| Institution: | 1. Department of Biomolecular Engineering, Tokyo Institute of Technology, B‐70, 4259 Nagatsuta, Midori‐ku, Yokohama, Japan;2. Quantum Chemistry Division, Graduate School of Science, Yokohama‐city University, Seto 22‐2, Kanazawa‐ku, Yokohama 236‐0027, Japan;3. Medical Beam Physics Laboratory, Division of Sustainable Energy and Environmental Engineering, Graduate School of Engineering, Osaka University, 2‐1 Yamadaoka, Suita, Osaka 565‐0871, Japan |
| Abstract: | To investigate the correlation between the wavelength dependence of ionization threshold fluence of target molecule in matrix‐assisted laser desorption/ionization by infrared (IR) laser and the IR absorption spectrum of matrix molecule, we have analyzed the IR absorption spectra of four matrix molecules using density functional theory and correlated ab initio molecular orbital method. The calculated IR absorption spectra of the isolated molecules showed more qualitative correlation with the wavelength dependence of ionization threshold fluence than those of the solid state structures. We can consider that a portion of matrix molecules lost the ordered crystal structure and that the transition to the diluted or isolated state occurred at the early process of IR laser irradiation. © 2012 Wiley Periodicals, Inc. |
| Keywords: | matrix‐assisted laser desorption/ionization by infrared laser density functional theory electron‐correlated second‐order Mø ller– Plesset calculation IR absorption spectra of solid structure and isolated molecule vibrational modes |