[pSer2, pSer5, pSer7]-CTD TFA

This phosphorylated CTD peptide, triply phosphorylated at serines 2, 5, and 7, serves as a specific substrate for CDK7 kinase assays. It is widely used in vitro to study transcription initiation, RNA polymerase II regulation, and kinase inhibitor screening in cancer and molecular biology research.