| AVS 61st International Symposium & Exhibition | |
| Applied Surface Science | Monday Sessions |
| Session AS+BI+MC+SS-MoA |
| Session: | The Liquid Interface & Depth Profiling and Sputtering with Cluster Ion Beams |
| Presenter: | Michael Durr, Justus Liebig University, Germany |
| Authors: | A. Portz, Justus Liebig University, Germany M. Baur, University of Applied Sciences, Germany C.R. Gebhardt, Bruker Daltonik GmbH, Germany M. Durr, Justus Liebig University, Germany |
| Correspondent: | Click to Email |
Desorption and ionization induced by neutral clusters (DINeC) can be employed as a soft and matrix-free method for transferring surface-adsorbed biomolecules into the gas phase. Using neutral clusters with polar constituents such as SO2, the impacting clusters do not only provide the energy necessary for desorption but also serve as a transient matrix in which the desorbing molecule is dissolved during the desorption process. As a consequence, desorption and ionization of oligopeptides and smaller proteins can proceed at comparably low energies of the impacting clusters and without any fragmentation [1]. Using a combination of DINeC and ion trap mass spectrometry, femtomol sensitivity was achieved for standard oligopeptides such as angiotensin II or bradykinin [2]; good ion-to-neutral ratio was observed [3].
In this contribution, we show that the signal of the intact molecules (M+H)+ is predominant even in the case of phospho- and glycopeptides, and typical fragments were observed only in low abundance. The origin of these fragments was investigated by comparison with ESI measurements of the original solution as well as of samples which have undergone a similar treatment as for the preparation of the DINeC samples. In that way, we could show that fragmentation takes place already during sample preparation and DINeC is suitable to directly measure such changes of the samples.
Samples with a multitude of components as obtained from realistic biotechnological processes such as tryptic digest of proteins were also successfully analyzed. Peptide mass fingerprint analysis was applied for the evaluation of the respective spectra with very good sequence coverage and protein score. When compared to ESI or MALDI, a substantial number of the unique peptides which were identified with DINeC were not detected with the other methods. Notably, even in the presence of a large excess of salt in the original solution clear spectra of the intact biomolecules were detected. The results are correlated to the very properties of the DINeC process. The method was furthermore successfully applied to a variety of different classes of molecules such as lipids, dye molecules, and pesticides.
References:
[1] C. R. Gebhardt, et. al., Angew. Chem. Int. Ed. 48, 4162 (2009).
[2] M. Baur, et al., Rapid Commun. Mass Spectrom. 28, 290 (2014).
[3] B.-J. Lee, et al., Rapid Commun. Mass Spectrom. 27, 1090 (2013).