Immunochemicals' Anti-DYKDDDDK (FLAG®) Kit for Immunoprecipitation is intended to provide a simple, reliable and convenient purification system for recombinant proteins containing the FLAG® epitope tag. Immunoprecipitation is a powerful technique for the isolation of proteins or protein complexes. Immunoprecipitation consists of several steps including cell lysis, binding of specific antigen to an antibody, antibody-antigen complex precipitation, precipitant wash steps and the dissociation of antigen from the complex. The FLAG® epitope tag is a small but highly immunogenic peptide DYKDDDDK (N-Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys-C), which allows fusion proteins to retain their original conformation and function. The hydrophilic character of FLAG® increases the likelihood that it will be located on the surface of the fusion protein where it is accessible to antibodies. Immunochemicals' Anti-DYKDDDDK (FLAG®) Kit for Immunoprecipitation allows a rapid and efficient immunoprecipitation and elution of an active FLAG® -tagged recombinant protein in less than 2 hours. The immunoprecipitation is performed with anti-FLAG® antibody coupled to agarose beads, which are generated by covalently linking agarose to a highly specific mouse monoclonal antibody raised against FLAG®. The provided protocol is a guideline. Any procedure can be altered according to specific experimental requirements. This kit is sufficient to perform 50 X 20 µL reactions and is stable for at least 1 year when stored as indicated.