Western blot of RFP recombinant protein detected with polyclonal anti-RFP antibody. Lane 1 shows no reaction against a GFP recombinant protein present in 10 ug of HeLa cell extract. Lane 2 shows a single band detected in 10 ug of a HeLa lysate containing RFP recombinant protein. polyclonal anti-RFP detects a 27 kDa band corresponding to the epitope tag RFP. A 4-12% Bis-Tris gradient gel (Invitrogen) was used for SDS-PAGE. The protein was transferred to nitrocellulose using standard methods. After blocking the membrane was probed with the primary antibody diluted 1:2,500 for 1 h at room temperature followed by washes and reaction with a 1:5,000 dilution of IRDye®800 conjugated Goat-a-Rabbit IgG [H&L] MX. IRDye®800 fluorescence image was captured using the Odyssey Infrared Imaging System developed by LI-COR. IRDye is a trademark of LI-COR, Inc. Other detection systems will yield similar results.