High-Level Expressionand Easy PurificationFinally, high levels of protein expressionand purification can be achieved withoutthe harsh elution conditions and largepurification tags that plague othersystems! The Affinity™ protein expres-sion and purification system provides thehighest levels of protein expression of anyprokaryotic system available. The T7RNA polymerase-based pCAL vectorsexpress cloned proteins as fusions withthe calmodulin-binding peptide (CBP)tag. The CBP-tagged proteins are easilypurified after only one pass throughcalmodulin resin. Both binding andelution of the CBP-tagged proteins are atneutral pH using mild buffer conditions.This means that the Affinity systemprovides an easy, gentle and effectivemethod for protein expression andpurification.