ALFA Selector ST

ALFA Selector ST (for “Super Tight”) is an innovative, high-affinity resin designed for the highly efficient pull-down of ALFA-tagged proteins.

Please look to our Technology Section for more information about the ALFA system.

ALFA Selector ST is based on a single-domain antibody (sdAb), which is covalently immobilized on 4% cross-linked agarose or agarose-magnetic beads and binds ALFA-tagged proteins with extraordinarily high affinity (Kd = 26 pM). Target proteins are efficiently released from ALFA Selector ST under acidic (e.g., 0.1 M glycin pH2.2) or denaturing conditions. The extremely tight interaction with ALFA-tagged proteins makes competitive elution using ALFA elution peptide inefficient. We recommend using ALFA Selector PE for competitive elution under physiological and room temperature condition conditions. For efficient elutions at 4°C, we recommend using the ALFA Selector CE

The innovative, oriented and highly selective attachment of the active sdAbs via a flexible linker guarantees optimal accessibility for target proteins and at the same time largely eliminates batch-to-batch variations. Due to the single-chain nature of sdAbs and their covalent attachment, no “leakage” of light and heavy chains from IgGs is observed even during elution with strongly denaturing and reducing conditions (e.g., SDS sample buffer). ALFA Selector ST thus features high affinity and superior capacity for ALFA fusion proteins while showing negligible non-specific background.

ALFA Selector ST is compatible not only with physiological buffers but also with high stringency buffers (see ALFA Selector Manual). ALFA Selector ST thus provides great freedom to adjust the binding and washing conditions to the experimental needs.