De Novo Sequencing of Peptides on Single Resin Beads by MALDI-FTICR Tandem Mass Spectrometry

An efficient approach in combinatorial chemistry is the synthesis of one-bead-one-compound peptide libraries. In contrast to synthesis and functional screening, which is performed in a largely automated manner, structure determination has been frequently laborious and time-consuming. Here we report an approach for de novo sequencing of peptides on single beads by matrix-assisted laser desorption/ionization Fourier transform ion cyclotron resonance (MALDI-FTICR) tandem mass spectrometry, using a resin with a photolinker for solid-phase peptide synthesis. Upon sorting out single beads, an efficient sample preparation on the MALDI target was developed that enables fragmentation upon irradiation of the bead-matrix mixture with the ultraviolet (UV)-MALDI laser, with enhanced yield of sequence-specific fragment ions at increased laser energy. This approach is illustrated by sequence determinations of two peptides from a library with sequences varying in a single amino acid; the feasibility with tandem-MS procedures and fragment ion assignment was ascertained by sustained off-resonance irradiation/collision induced dissociation (SORI/CID) and infrared multiphoton dissociation (IRMPD) fragmentation.

Graphical AbstractMALDI-FTICR-tandem mass spectrometry enables de novo sequencing of peptide libraries bound to single resin beads, using a resin-bound photolinker and in-situ fragmentation upon UV-MALDI irradiation of the bead-matrix mixture.Figure optionsDownload full-size imageDownload high-quality image (77 K)Download as PowerPoint slide