**Author details**

*Proteoforms - Concept and Applications in Medical Sciences*

A huge progress has been made in the field of TDMS, allowing the identification and comprehensive analysis of the composition of atoms of proteoforms, especially if they are smaller than 30 kDa. TDMS analysis of larger proteoforms still is more challenging. However, until today the most critical point is the purification of a proteoform towards near homogeneity or at least the significant reduction of complexity of the sample, which is desorbed and ionized into a tandem mass spectrometer for TDMS. A low complexity of the composition of a protein mixture entering the MS still is mandatory for getting high quality spectra. Thus, efficient separation methods are needed for obtaining fractions with low complexity. For developing strategies for separating proteoforms, therapeutic proteins are well suited, however challenging because of their heterogeneity. In depth separation of the proteoforms of a therapeutic protein requires the combination of fractionation techniques based on orthogonal mechanisms. In addition, the combination of gradient chromatography and displacement chromatography will add further opportunities for successful

The authors would like to thank the European Research Council (ERC) for funding the A4B project by the Horizon 2020 Marie Sklodowska-Curie Action ITN 2017 of the European Commission (H2020-MSCA-ITN-2017; under the European Union's Horizon 2020 programme for research and innovation under grant agree-

**5. Conclusion**

separations.

**Acknowledgements**

ment No 765502).

**Abbreviations**

AEX anion exchange

CEX cation exchange

ADCs antibody-drug-conjugates CE capillary electrophoresis CGE capillary gel electrophoresis CIEF capillary isoelectric focusing CZE capillary zone electrophoresis

CID collision-induced dissociation ECD electron capture dissociation ETD electron transfer dissociation

HCD higher energy collisional dissociation HAP hydroxyapatite-chromatography

HILIC hydrophilic interaction chromatography HIC hydrophobic interaction chromatography IMAC immobilized metal-affinity-chromatography

ESI electrospray ionization GE gradient elution

ETHcD electron transfer higher energy collisional dissociation

**Conflict of interest**

The authors declare no conflict of interest.

**36**

Siti Nurul Hidayah† , Manasi Gaikwad† , Laura Heikaus and Hartmut Schlüter\* Mass Spectrometric Proteomics, Institute of Clinical Chemistry and Laboratory Medicine, University Medical Center Hamburg-Eppendorf, Hamburg, Germany

\*Address all correspondence to: hschluet@uke.de

† These authors have equally contributed as first authors.

© 2019 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
