Stat3β monoclonals specifically detect Stat3β protein in cell protein extracts. Plasmids encoding fusion proteins Stat3α-GFP and Stat3β-GFP were transiently transfected into HEK 293T cells. Extracts (100 µg protein) from mock or plasmid transfected (48 h) cells were separated by SDS-PAGE, transferred to nitrocellulose membrane and replicate blots probed for (A) Stat3β using the three monoclonal antibodies 516 G10H9, 954 E9E7 and 1488 G6G5 and (B) Stat3α (Clone D1A5), total Stat3 (clone 124H6) and GAPDH and visualized by chemiluminiscence. Various dilutions (ranging from 1:300 to 1:10,000) of the three Stat3β monoclonal antibodies 516 G10H9 (C), 954 E9E7 (D) and 1488 G6G5 (E) were used to probe 100 µg protein from 293T cells transiently transfected with plasmids encoding fusion proteins Stat3α-GFP and Stat3β-GFP and visualized by chemiluminiscence.