Protein-protein cross-linking and human health: the challenge of elucidating with mass spectrometry

Introduction: In several biomedical research fields, the cross-linking of peptides and proteins has an important impact on health and wellbeing. It is therefore of crucial importance to study this important class of posttranslational modifications in detail. The huge potential of mass spectrometric technologies in the mapping of these protein-protein cross-links is however overshadowed by the challenges the field has to overcome. Areas covered: In this review, we summarize the different pitfalls and challenges the protein-protein cross-linking field is confronted with while elucidating them via mass spectrometry approaches. We additionally focus on native disulfide bridges as an exemplar and provide some examples of cross-links that are important in the biomedical field. Expert commentary: The current flow of methodological improvements, mainly from the chemical cross-linking field, has delivered a significant contribution to deciphering native and insult-induced cross-links. Although currently not yet possible, the cross-linking field is well on the way towards a more automated analysis of cross-links in raw mass spectrometry data that will boost its potential in biomedical applications.