The Twin Strep-tag II, while retaining the high specificity and mild purification conditions of the Strep-tag II, boasts an even higher affinity. Consequently, it can be utilized for direct purification of the target protein from culture supernatants. Furthermore, its ability to withstand various buffer conditions and additives, such as high salt concentrations, surfactants, reductants, metal ions, and chelating agents, renders it a versatile tag for a wide range of proteins. The pSmart VI vector is a modification of the pET-28a vector, primarily achieved by the insertion of the SUMO protein's nucleic acid sequence downstream of the tag to enhance protein solubility. Multiple cloning sites have been preserved to facilitate the insertion of gene fragments. Additionally, the inclusion of the RFP tag's nucleic acid sequence serves as a positive control for protein expression.