Multivariate Analysis of MALDI Imaging Mass Spectrometry Data of Mixtures of Single Pollen Grains
Mixtures of pollen grains of three different species (Corylus avellana, Alnus cordata, and Pinus sylvestris) were investigated by matrix-assisted laser desorption/ionization time-of-flight imaging mass spectrometry (MALDI-TOF imaging MS). The amount of pollen grains was reduced stepwise from > 10 to single pollen grains. For sample pretreatment, we modified a previously applied approach, where any additional extraction steps were omitted. Our results show that characteristic pollen MALDI mass spectra can be obtained from a single pollen grain, which is the prerequisite for a reliable pollen classification in practical applications. MALDI imaging of laterally resolved pollen grains provides additional information by reducing the complexity of the MS spectra of mixtures, where frequently peak discrimination is observed. Combined with multivariate statistical analyses, such as principal component analysis (PCA), our approach offers the chance for a fast and reliable identification of individual pollen grains by mass spectrometry.
KeywordsMALDI imaging MS Pollen grains Multivariate statistics Hierarchical cluster analysis Principal component analysis
The authors thank Thomas Dürbye of the Botanic Garden and Botanical Museum Berlin-Dahlem for their support in sample collection.
Janina Kneipp received funding from the European Research Council (ERC) (grant no. 259432).
- 15.Adhami, F., Leitzenberger, I., Wagner, S., Scheiner, O., Breiteneder, H.: Recombinant hevein and hevein-like domains from Hevea latex, avocado and banana bind cross-reactive IgE from latex-allergic patients. Allergy. 57, 82–83 (2002)Google Scholar
- 21.Raftery, M.J., Saldanha, R.G., Geczy, C.L., Kumar, R.K.: Mass spectrometric analysis of electrophoretically separated allergens and proteases in grass pollen diffusates. Respir. Res. 4, (2003)Google Scholar
- 22.Westphal, S., Kolarich, D., Foetisch, K., Lauer, I., Altmann, F., Conti, A., Crespo, J.F., Rodriguez, J., Enrique, E., Vieths, S., Scheurer, S.: Molecular characterization and allergenic activity of Lyc e 2 (beta-fructofuranosidase), a glycosylated allergen of tomato. Eur. J. Biochem. 270, 1327–1337 (2003)CrossRefGoogle Scholar