Soft cluster-induced desorption and ionization of biomolecules—Influence of surface load and morphology on desorption efficiency

Abstract

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Desorption/ionization induced by neutral cluster impact as a soft and efficient ionization source for ion trap mass spectrometry of biomolecules

“…We would like to discuss our results first with respect to the desorption and ionization of DSPC and rhodamine molecules. To date, DINeC experiments have been restricted to oligopeptides and alkali halides . With the desorption and ionization of a phospholipid and dye molecules, two new classes of molecules are shown to be accessible by desorption and ionization induced by neutral cluster impact thus demonstrating the more general applicability of DINeC as an ion source for chemical analysis by means of mass spectrometry.…”

“…To date, DINeC experiments have been restricted to oligopeptides and alkali halides. [9,10,[12][13][14] With the desorption and ionization of a phospholipid and dye molecules, two new classes of molecules are shown to be accessible by desorption and ionization induced by neutral cluster impact thus demonstrating the more general applicability of DINeC as an ion source for chemical analysis by means of mass spectrometry. and (c), the main peak (m/z 443) of the initial spectrum was isolated and fragmented by means of CID.…”

“…We interpret this as further indication of the influence of water in the sample on the desorption/ionization mechanism. [10] To illustrate the capability of DINeC for the analysis of more complex samples, the products of a tryptic digest of BSA were drop cast on a SiO 2 surface and exposed to the neutral cluster beam. The resulting mass spectrum is shown in Fig.…”

“…[5][6][7][8] In contrast to the techniques using charged (non-reactive) primary particles, we have recently shown that a beam of neutral SO 2 clusters can also be employed for very soft and matrix-free desorption and ionization of oligopeptides. [9][10][11] With the high dipole moment of the SO 2 molecules (1.6 debye), the impacting SO 2 clusters do not only provide the energy necessary for the desorption, but also serve as a transient matrix in which the desorbing molecule is dissolved during the desorption process; as a consequence desorption takes place at comparably low cluster energies (<1 eV/molecule). Shattering of the cluster during and after surface impact then leads to a rapid redistribution of the system's energy thus avoiding heating and fragmentation of the desorbing molecules.…”

Quantification of the ionization probability during desorption/ionization of oligopeptides induced by neutral cluster impact

“…[16] In the case of surface-adsorbed biomolecules, this allows for desorption and ionization of oligopeptides at comparably low energy per cluster constituent without any fragmentation of the biomolecules. [15,17] The impacting cluster not only provides the energy for desorption of the biomolecule but also serves as a transient matrix that facilitates the desorption process. In addition, shattering of the cluster during its impact on the surface leads to a rapid redistribution of the system's energy on the picosecond time scale and thus an efficient cooling of the desorbed molecules, [15] which also contributes to the fragmentation-free nature of DINeC.…”