GAS cultures were grown in the presence of 19b with or without competitor 3, then subjected to UV crosslinking conditions. The cells were lysed and a fluorescent Alexa Fluor 488 moiety was appended to probe-protein adducts via click chemistry, then proteins were isolated and separated via SDS-PAGE. A: Fluorescent visualization of proteins from crosslinking and competition experiments with 19b on PAGE gel. B: Total protein stain of gel with Sypro Ruby stain. Lane 1: 100 μM 19b; Lane 2: 10 μM 19b; Lane 3: 10 μM 19b + 100 μM 3; Lane 4: 1 μM 19b; Lane 5: 1 μM 19b + 100 μM 3; Lane 6: 100 μM 19b, no UV crosslinking; Lane 7: 10 μM 19b, no UV crosslinking; Lane 8: 1 μM 19b, no UV crosslinking; Lane 9: no probe, no UV crosslinking.