A shift in both the excitation and the emission toward longer wavelength helps overcome problems of compound autofluorescence in screening assays. One such substrate is the rhodamine based ubiquitin-eN-(aN-tetramethyl-rhodamine)lysine (Ubiquitin-Lys-TAMRA), which mimics the naturally occurring isopeptide bond Between the C-terminus of ubiquitin and the e-amino group of a lysine residue of an ubiquitinated protein (Tirat et al., 2005). Cleavage of the isopeptide bond results in a decrease of fluorescence polarization, which makes Ubiquitin-Lys-TAMRA suitable  for high-throughput screening applications (Hassiepen et al., 2007). Fluorescence polarization, in contrast to fluorescence intensity, allows a ratiometric read-out of the activity and is thus less sensitive to autofluorescing or quenching caused by test compounds (Tirat et al.,2005).

References:

Hassiepen U, Eidhoff U, Meder G, Bulber JF, Hein A, Bodendorf U, et al. (2007) A sensitive fluorescence intensity assay for deubiquitinating proteases using ubiquitin-rhodamine110-glycine as substrate. Anal Biochem 371, 201-207.

Tirat A, Schilb A, Riou V, Leder L, Gerhartz B, Zimmermann J, et al. (2005) Synthesis and characterization of fluorescent ubiquitin derivatives as highly sensitive substrates for the deubiquitinating enzymes UCH-L3 and USP-2. Anal Biochem 343, 244-255.

Ubiquigent Limited is a specialist developer and supplier of Drug Discovery Services, high quality Research Tools and Chemistry to the life science research community worldwide.

Ubiquigent’s scientific and business interests have a clear focus; namely the ubiquitin, ubiquitin-like, and integrated signalling systems.

The Company has established its scientific and business credentials with both academic researchers undertaking fundamental scientific discovery and pharmaceutical and biotechnology company scientists exploring the potential of ubiquitin cascade-focused drug discovery.

Ubiquigent benefits from high calibre backing including from private US investors, the UK Medical Research Council, and the University of Dundee. The Company’s headquarters and laboratory operations are based in the UK and are located in a state-of-the-art facility adjacent to the MRC Protein Phosphorylation and Ubiquitylation Unit at the University of Dundee (both founded by Professor Sir Philip Cohen). In addition to Ubiquigent’s own facilities and capabilities, such proximity provides ready access to a huge range of additional scientific expertise (1,000+ life-science researchers on site), technological competencies, and assay and analytical platforms.

Ubiquigent staff have a wealth of scientific experience, technological competencies and commercial expertise, gained from within academia, the life science research reagents and services sector, and the pharmaceutical industry, that enables the Company to offer a level of understanding and service to its customers and clients worldwide that few companies may match.