Their experimental approach involved chemical modifications of PLA2s of variable toxicity, followed by a detailed assessment of the changes in toxicity of modified proteins, using a variety of pharmacological assays including lethality, effects on neuromuscular preparations, cardiotoxicity, effects on coagulation, and hemolysis. A relevant innovation in the work of Rosenberg and colleagues was the evaluation of enzymatic activity not only on phospholipids in vitro, as was traditionally done, but also the assessment of the ability of these PLA2s to hydrolyze phospholipids in various tissues in vivo, thus allowing the analysis of enzymatic activity on relevant targets.