ALFA Selector PE (for "peptide elutable") is an innovative affinity resin designed for the highly efficient purification of native ALFA-tagged target proteins under physiological conditions. For general information about the ALFA system click here. ALFA Selector PE is based on a high-affinity (Kd = 11 nM) single-domain antibody (sdAb) that is covalently immobilized on 4% cross-linked agarose beads. ALFA Selector PE is optimized for an efficient competitive elution under physiological conditions using ALFA elution peptide. For this purpose, every unit of ALFA Selector PE is supplied with 10 mg of ALFA elution peptide, which is sufficient for 25 mL of elution buffer. Alternatively, elution can be performed under acidic or denaturing conditions. The innovative, oriented and selective attachment via a flexible linker guarantees a high accessibility of the sdAbs and 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 during elution, even under harsh conditions (e.g. SDS sample buffer). ALFA Selector PE thus features high affinity and superior capacity for ALFA fusion proteins while showing negligible non-specific background. ALFA Selector PE is compatible not only with physiological buffers but also with high stringency buffers (see Product Data Sheet). ALFA Selector PE thus provides great freedom to adjust the binding and washing conditions to the experimental needs.