Mass Spectrometry



Mass Spectrometry (MS) is mainly employed in the Schubert group for the elucidation of the structures of compounds which are synthesized within the Schubert group, such as homopolymers, block- and random copolymers, terpyridine complexes and sugar molecules. There are three ionization techniques available within the group, e.g. matrix-assisted laser desorption/ionization (MALDI), electrospray ionization (ESI), and atmospheric pressure chemical ionization (APCI). All three ionization techniques are considered as powerful tools. Especially in the polymer analysis, since the determination of the end groups, repeating units, average molar masses, and the polydispersity index (PDI) can be obtained. Additionally, the MS/MS analysis provides structural information. An example of a mass spectrum obtained from poly(styrene) (PS) using MALDI MS is presented in Figure 1. The average molar masses can be calculated from the distribution of the peaks with the assistance of a suitable software.

When the polymer samples are much more complex, 2-dimensional chromatography prior to MALDI or ESI MS is employed. Since the interpretation of the MALDI MS/MS results of polymer samples is very time consuming, we are collaborating with Prof. S. Böcker (Institute for Informatics, Friedrich-Schiller-University Jena) to automatically identify the structure of the monitored fragment ions. An example of an ESI analysis of a ruthenium-terpyridine complex is given in Figure 2. The calculated isotopic pattern of the recorded doubly charged ion fits exactly to the measured ones.

picture. Figure 1. MALDI MS spectrum of PS using DCTB as matrix and AgTFA as ionization salt.


Figure 2. (a) ESI MS analysis of a ruthenium-terpyridine complex, (b) the inset shows the experimental and calculated isotope patterns of the doubly charged ion of the ruthenium-terpyridine complex, (c) schematic representation of the structure of the analyzed ruthenium-terpyridine complex.
Another interest in the Schubert group is MALDI-imaging MS, a relatively new technique, which permits the direct analysis and determination of the distribution of molecules in tissue sections. Using this emerging technology ion images are generated from the analyzed tissue sections. Several collaborations in this field:

* PD Dr. F. Eggeling and L. Wehder (Core Unit Chip Application, Institute for Human Genetic and Anthropology, University Clinical Center Jena) MALDI-Imaging MS of human tumor tissue

* Dr. D. Hölscher (Department of Entomology, Mass Spectrometry Research Group, and Biosynthesis/NMR Research Group, Max-Planck-Institute for Chemical Ecology) Matrix-free UV-laser desorption/ionization (LDI) mass spectrometry imaging at the single – cell level: distribution of secondary metabolites of different plant species

* Dr. G. Schneider and K. Otto (Hospital for Ear, Nose and Throat Diseases, University Clinical Center Jena) MALDI-imaging MS of protein responses to polymer based implants

* Prof. A. Stallmach and C. Marquardt (Hospital for Internal Medicin II, Department Gastroenterology, University Clinical Center Jena) Identification of new protein biomarkers of the hepatocellular carcinoma by MALDI-imaging MS


Figure 3. Overlaid ion images of a rabbit tissue section.