Specific Decoration of a Discrete Bismuth Oxido Cluster by Selected Peptides towards the Design of Metal Tags

Abstract Metal tags find application in a multitude of biomedical systems and the combination with laser ablation inductively coupled plasma mass spectrometry (LA‐ICP‐MS) offers an opportunity for multiplexing. To lay the foundation for an increase of the signal intensities in such processes, we herein present a general approach for efficient functionalization of a well‐defined metal oxido cluster [Bi 6 O 4 (OH) 4 (SO 3 CF 3 ) 6 (CH 3 CN) 6 ]⋅2 CH 3 CN ( 1 ), which can be realized by selecting 7mer peptide sequences via combinatorial means from large one‐bead one‐compound peptide libraries. Selective cluster‐binding peptide sequences ( CBS ) for 1 were discriminated from non‐binders by treatment with H 2 S gas to form the reduction product Bi 2 S 3 , clearly visible to the naked eye. Interactions were further confirmed by NMR experiments. Extension of a binding peptide with a maleimide linker ( Mal ) introduces the possibility to covalently attach thiol‐bearing moieties such as biological probes and for their analysis the presence of the cluster instead of mononuclear entities should lead to an increase of signal intensities in LA‐ICP‐MS measurements. To prove this, CBS ‐ Mal was covalently bound onto thiol‐presenting glass substrates, which then captured 1 effectively, so that LA‐ICP‐MS measurements demonstrated drastic signal amplification compared to single lanthanide tags.