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Anal Chem. 2018 Nov 6;90(21):12527-12535. doi: 10.1021/acs.analchem.8b02398. Epub 2018 Oct 12.

Multiplexed Middle-Down Mass Spectrometry as a Method for Revealing Light and Heavy Chain Connectivity in a Monoclonal Antibody.

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Ecole Polytechnique Fédérale de Lausanne , 1015 Lausanne , Switzerland.
Spectroswiss , EPFL Innovation Park, 1015 Lausanne , Switzerland.
Institute for Energy Problems of Chemical Physics , Russian Academy of Sciences , 119334 Moscow , Russia.
Centre d'Immunologie Pierre Fabre , 74160 St. Julien-en-Genevois , France.
Moscow Institute of Physics and Technology State University , 141707 Dolgoprudny , Moscow Region , Russia.
Thermo Fisher Scientific GmbH , 28199 Bremen , Germany.


Pairing light and heavy chains in monoclonal antibodies (mAbs) using top-down (TD) or middle-down (MD) mass spectrometry (MS) may complement the sequence information on single chains provided by high-throughput genomic sequencing and bottom-up proteomics, favoring the rational selection of drug candidates. The 50 kDa F(ab) subunits of mAbs are the smallest structural units that contain the required information on chain pairing. These subunits can be enzymatically produced from whole mAbs and interrogated in their intact form by TD/MD MS approaches. However, the high structural complexity of F(ab) subunits requires increased sensitivity of the modern TD/MD MS for a comprehensive structural analysis. To address this and similar challenges, we developed and applied a multiplexed TD/MD MS workflow based on spectral averaging of tandem mass spectra (MS/MS) across multiple liquid chromatography (LC)-MS/MS runs acquired in reduced or full profile mode using an Orbitrap Fourier transform mass spectrometer (FTMS). We first benchmark the workflow using myoglobin as a reference protein, and then validate it for the analysis of the 50 kDa F(ab) subunit of a therapeutic mAb, trastuzumab. Obtained results confirm the envisioned benefits in terms of increased signal-to-noise ratio of product ions from utilizing multiple LC-MS/MS runs for TD/MD protein analysis using mass spectral averaging. The workflow performance is compared with the earlier introduced multiplexed TD/MD MS workflow based on transient averaging in Orbitrap FTMS. For the latter, we also report on enabling absorption mode FT processing and demonstrate its comparable performance to the enhanced FT (eFT) spectral representation.

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