Heteroleptic Ruthenium(II) Complexes with Bathophenanthroline and Bathophenanthroline Disulfonate Disodium Salt as Fluorescent Dyes for In-Gel Protein Staining

The in-gel detection of proteins for various proteomic experiments is commonly done with the fluorescent Ru-II tris(bathophenanthroline disulfonate) complex (Ru(BPS)(3)), which is more cost-effective compared to commercial Ru-based formulations but requires tedious procedures for its preparation and strongly acidic staining conditions. Herein, we report the synthesis and characterization of heteroleptic Ru-II complexes Ru(BPS)(2)(BP) and Ru(BPS)(BP)(2) containing bathophenanthroline (BP) and bathophenanthroline disulfonate disodium salt (BPS) in comparison with Ru(BPS)(3). It was shown by fluorescent and UV-vis measurements that novel Ru-II complexes were excitable in both UV and visible light, close to emission bands of classical lasers, which is important for successful in-gel protein detection. Novel fluorescent dyes demonstrated improved protein detection in comparison with commercially available SYPRO Ruby staining solution. In addition, unlike commonly used staining protocols, staining with Ru(BPS)(BP)(2) can be performed at nearly neutral pH, thereby reducing artificial post-translational modifications (PTMs).