A general soft ionization method for mass spectrometry: Resonance‐enhanced multi‐photon ionization of biomolecules

Abstract

We show here that 'double-barrelled' laser desorptionJresonance-enhanced multi-photon ionization mass spectrometry has many advantages over traditional single-step desorptionJionuation techniques, particularly if combined with Reflectron-Time-of-Flight mass analysers. We demonstrate the effectiveness of this technique for large labile biomolecules, namely native chlorophylls, porphyrins and a peptide, as examples of structural and mass analysis.

Direct determination of polycyclic aromatic hydrocarbons in solid matrices using laser desorption/laser photoionization ion trap mass spectrometry

“…It should also be noted that very little fragmentation was observed in any of the trials performed. This result is consistent with those seen previously in the literature for both PAHs [11, 30 -32] and other large molecules [9,12,18,37] with the two-laser set-up. In order to determine the reproducibility of the standard samples, several trials were preformed in which one standard was exposed to several thousand laser shots; the result is provided in Figure 3 which is a plot of the magnitude (integrated pyrene peak areas) of the pyrene signal as a function of the number of laser shots for a sample containing 10 mol pyrene/gram charcoal.…”

“…It was first developed for mass spectrometry of involatile and/or thermally labile organics in the mid-1980s [7][8][9]. Since that time it has been further developed and used for a variety of solid samples including polymers [10], soot and coal tar [11], dyes [12], and molecular adsorbates [13].…”

Gas-phase formation of large neutral alkaline-earth metal tryptophan complexes

“…G as-phase investigations of organic molecules have received an enormous and still increasing attention since the successful establishment of various laser desorption [1][2][3] and electrospray ionization techniques [4]. The majority of studies so far focused on the generation and use of ionic species.…”

“…The majority of studies so far focused on the generation and use of ionic species. Our work, presented here, focuses on the gas-phase formation of neutral biomolecular clusters as did already some very early studies in the field [1]. Such experiments are often motivated by the desire to better identify the role of solvation and desolvation for the relative importance of various binding forces in organic clusters and molecules [5].…”

“…Ionization methods used in the past have been as diverse as the molecules· under investigation: UV multi-photon ionization [1] was in competition with single-photon ionization using VUV lamps [IS], VUV lasers [16], dye tagging of molecules [17], femtosecond ionization (18], or even thermionic emission of electrons (19]. But it has still remained a challenge to find reproducible methods for photoionizing biomolecules and complexes with masses exceeding 3000 u [17,20,21].…”