Western blot analysis of azido-BSA – Biotin-azide conjugation using different protein loading: lanes 1–5, 2 µg per lane and lanes 6–7, 2 µg per lane. Lanes 2,7: photo-DIBOD 1a, azido-BSA and Biotin-azide irradiated; Lanes 3,8: 2a, azido-BSA, and Biotin-azide incubated overnight; Lanes 4,9: photo-DIBOD 1a, azido-BSA, and Biotin-azide incubated overnight in the dark; Lane 5,10: azido-BSA and Biotin-azide incubated overnight.