Conversion of ProVP16-I to ProVP16-II and VP16. ProVP16-I was incubated in THF/2% HCl, and samples were periodically analyzed by HPLC at the indicated time points (A). Hydrolytic activation of ProVP16-II was determined in PBS at the pH levels indicated (B). ProVP16-I (3 mM) was incubated in PBS solutions and samples were periodically analyzed by HPLC. The percent conversion was calculated from areas under the curve determined by peak integration.