Site specific chemoselective labelling of proteins with robust and highly sensitive Ru(ii) bathophenanthroline complexesElectronic supplementary information (ESI) available: Synthesis of various ruthenium(ii) complexes used and methods for labelling of peptide and proteins are described. See DOI: 10.1039/c2ob06684j

The bioorthogonal and chemoselective fluorescence labelling of several cell-free synthesized proteins containing a site-specifically incorporated azido amino acid was possible using different alkyne-functionalized Ru( ii ) bathophenanthroline complexes. We were able to achieve a selective labelling even in complex mixtures of proteins despite the fact that ruthenium dyes normally show a high tendency for unspecific interactions with proteins and are commonly used for total staining of proteins. Since the employed Ru complexes are extremely robust, photo-stable and highly sensitive, the approach should be applicable to the production of labelled proteins for single molecule spectroscopy and fluorescence-based interaction studies. The bioorthogonal and chemoselective fluorescence labelling of several cell-free synthesized proteins containing a site-specifically incorporated azido amino acid using extremely robust, photo-stable and highly sensitive alkyne-functionalized Ru( ii ) bathophenanthroline complexes was achieved via a click reaction.