Our Ultra-Pure Actin and Pure-Actin differ in their purity and pricing. Both are extracted from rabbit skeletal muscle using an adaptation of the method of Spudich and Watt (1971) and lyophilized by an adaptation of the method of Dráberová et al. (2010). Ultra-Pure Actin is >99% pure and >90% active, while Pure Actin is >90% pure and >80% active. Activity is assessed by an actin pelleting assay.