Lee, J., Yu, P., Xiao, X. and Kodadek, T.
Notes: In this paper, researchers were looking for efficient chromophores for singlet oxygen generation used for chromophore-assisted light inactivation (CALI) of proteins. The HaloTag® protein and firefly luciferase were used to test how well the chromophores performed in crude extracts and living cells. The expression vector for an epitope-tagged Luciferase-HTP protein, 3X Flag-Luc-HTP-Myc, was constructed using firefly luciferase amplified from the pGL3-Basic Vector and HaloTag® (HTP) amplified from the pHT2 Vector. The fusion protein was tested for labeling with a HaloTag® biotin ligand by transfecting HeLa cells with 8μg of 3X Flag-Luc-HTP-Myc plasmid and 80ng of pRL-SV40 Vector. After transfection, cells were lysed with Passive Lysis Buffer and 2μl of HeLa cell lysate was diluted in 48μl of PBS + BSA and incubated for 30 minutes at room temperature with increasing concentrations of a biotin-HT ligand. The samples then were incubated with streptavidin-agarose for 30 minutes at room temperature, centrifuged and the luciferase activity of 20μl of supernatant was measured using the Dual-Luciferase® Reporter Assay System. The fusion protein was also tested using two chromophore ligands, ruthenium(II)tris-bipyridyl (Ru-HaloTag®[HT]) and fluoroscein-HT at a concentration of 100nM, and both were successful as measured by the Dual-Luciferase® Reporter Assay System. An in vivo CALI was performed by transfecting HeLa cells with 100ng of 3X Flag-HTP-Luc-Myc plasmid and 1ng of pRL-SV40 Vector for 15 hours, and treating the cells with Ru-HT or F-HT for 3 hours. The cells were then irradiated for 30 minutes, placed in the dark for 30 minutes, then the cells were lysed and analyzed with the DLR Assay. (3954)