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MTS-diazirine – Photocrosslinker

Redbrick Molecular sells a collection of photo-crosslinkers that enable the study of interactions between proteins and other biomolecules through photo-affinity labelling.  The MTS-diazirine product and related compounds were developed by Prof Andy Wilson and Prof Sheena Radford FRS at The University of Leeds.

Chemical cross-linking mass-spectrometry (XL-MS) is a powerful methodology to map interactions between ligands and biomacromolecules and to potentially track changes over time.   The Wilson and Radford groups at The University of Leeds have designed four new photo-crosslinking (PXL) reagents that can be used to specifically label free thiols through light-sensitive maleimido or methanethiosulfonate (MTS) groups.  Labelled materials can then be studied using mass-spectrometry work flows.

The Leeds MTS and maleimido photocrosslinkers are based on light sensitive diazirines, which offer advantages over alternative crosslinking groups such as benzophenones and aryl nitrenes.  The Wilson/Radford reagents react rapidly and indiscriminately upon light radiation and ensure supramolecular connectivity is accurately captured.

These labels can be applied in the structural analyses of protein–protein interactions using PXL-MS by conjugating them to thiol-containing bait peptides/proteins and subsequent crosslinking with partner proteins.


You can now buy MTS-diazirine directly from Redbrick Molecular but we have also made it available via Fluorochem Ltd –

Photo activated crosslinkers & photo-affinity labelling

Protein-protein interactions (PPIs) can trigger a wide range of biological signalling pathways. Different techniques have been developed to study PPIs, including affinity-based probes and photo-affinity labelling. Photo-affinity labelling is one of the most common methods used to study PPIs.  Benzophenone, aryl azide, and diazirine species are traditionally used as photo-crosslinkers because they can be used to directly modify neighbouring molecules through photoirradiation.

The methanethiosulfonate or maleimide functional groups in the Redbrick Molecular photo-crosslinkers are designed to specifically modify cysteine residues that are either naturally occurring or engineered into a “bait” peptide or protein. Direct conjugation of these compounds to cysteine residues makes them suitable labels for proteins and peptides to facilitate structural proteomics studies. The second functional group – the diazirine – is a photoactivated cross-linking group that upon irradiation with 365 nm UV light generates a highly reactive carbene that inserts into proximal functional groups (including C-H, N-H, O-H groups etc) on biomacromolecules which interact with the bait, generating a covalently trapped complex.  Reaction of the methanethiosulfonate functional group with cysteine generates a disulfide bond; cleavage of this bond following cross-linking simplifies analysis of crosslinked complexes.

Customers can purchase the Tag-Transfer compounds individually or as a collection.  Click here to see our full range!

Further information

  • Tag-Transfer compounds and all subsequently labelled proteins should be handled in the dark (i.e. by exclusion of the light) as much as possible and stored at -20°C in amber vials or vials wrapped in aluminium foil.
  • The Tag-Transfer products are soluble in DMSO or DMF to at least 10 mg/ml.
  • Labelling of cysteine residues should be performed in buffer containing a small amount <10% of DMSO or DMF.
  • Reductive removal of the bait initially transfers a thiol-containing fragment of the crosslinking reagent onto the target that can be alkylated and located by MS sequencing and/or exploited for enrichment, enabling the detection of low abundance crosslinks.
  • See the Protocol in the Documents tab for further information.


For further technical details please see the papers published by Prof Wilson and Prof Radford in November 2018 and March 2019 – ;!divAbstract

Wilson Lab

The Wilson Group is based in the School of Chemistry at The University of Leeds. Its members are also part of the Astbury Centre for Structural Molecular Biology.  The group are interested in the application of synthetic molecules to problems in Chemical Biology and Materials Science.  Find out more from the group pages.

WeightPrice (GBP)
25 mg200
Supporting Documents
Specification sheet
Rapid Mapping of Protein Interactions Using Tag‐Transfer Photocrosslinkers - Reference
Design and synthesis of cysteine-specific labels for photo-crosslinking studies