Click Chemistry Generated Model DNA-Peptide Heteroconjugates as Tools for Mass Spectrometry

UV cross-linking of nucleic acids to proteins in combination with mass spectrometry is a powerful technique to identify proteins, peptides, and the amino acids involved in intermolecular interactions within nucleic acid protein complexes. However, the mass spectrometric identification of crosslinked nucleic acid protein heteroconjugates in complex mixtures and MS/MS characterization of the specific sites of cross-linking is extremely challenging. As a tool for the optimization of sample preparation, ionization, fragmentation, and detection by mass spectrometry, novel synthetic DNA peptide heteroconjugates were generated to act as mimics of UV cross-linked heteroconjugates. Click chemistry was employed to cross-link peptides to DNA oligonucleotides. These heteroconjugates were fully characterized by high resolution FTICR mass spectrometry and by collision-induced dissociation (CID) following nuclease 131 digestion of the DNA moiety to a single nucleotide monophosphate. This allowed the exact site of the cross-linking within the peptide to be unambiguously assigned. These synthetic DNA-peptide heteroconjugates have the potential to be of use for a variety of applications that involve DNA-peptide heteroconjugates.