Summary Nuclear magnetic resonance (NMR) spectroscopy can be used to determine the structure, dynamics and interactions of proteins. However, protein NMR requires stable isotope labelling for signal detection. The cells used for the production of recombinant proteins must therefore be grown in medium containing isotopically labelled substrates. Stable isotope labelling is well established in Escherichia coli, but bacteria are only suitable for the production of simple proteins without post‐translational modifications. More complex proteins require eukaryotic production hosts, but their growth can be impaired by labelled media, thus reducing product yields and increasing costs. To address this limitation, we used media supplemented with isotope‐labelled substrates to cultivate the tobacco‐derived cell line BY‐2, which was then cast into plant cell packs (PCPs) for the transient expression of a labelled version of the model protein GB1. Mass spectrometry confirmed the feasibility of isotope labelling with 15N and 2H using this approach. The resulting NMR spectrum featured a signal dispersion comparable to recombinant GB1 produced in E. coli. PCPs therefore offer a rapid and cost‐efficient alternative for the production of isotope‐labelled proteins for NMR analysis, especially suitable for complex proteins that cannot be produced in microbial systems.

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The applicability of monoclonal antibodies (mAbs) in therapeutic research continues to rise — they now account for almost 50% of protein‐based drugs. Monitoring their quality as well as binding properties are critical as these parameters provide insight into mAb functionality and efficacy as potential drugs.Here we study trastuzumab, a monoclonal antibody that has been used to successfully treat patients with certain forms of breast cancer. Trastuzumab acts by binding to and interfering with the HER2/neu receptor in cancer patients. Using two complementary technologies, we examine how targeted oxidation affects trastuzumab structure and therefore its binding capabilities to protein A. First, a rapid analysis of oxidation‐induced changes in mAb folding and stability was performed. The same samples were then analyzed to determine how oxidation compromises mAb interactions. Oxidational stress directly correlated with weaker binding affinities of the Fc region towards protein A, showcasing fast and accurate characterization of trastuzumab sample quality.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.