Pancreatic Islet Isolation Grade. Suggested for pancreatic islet isolation. Prepared to contain lower tryptic activity levels. Activity: ≥160U per mg solid. Unit Definition: One unit liberates peptides from collagen equivalent in ninhydrin color to 1.0μmol of L-leucine in 5 hr. at pH 7.4 and 37°C in presence of calcium ions. Dialyzed, lyophilized.