Mechanism of vesicle explosion. (A) Schematic diagram for radical-mediated oxidation of bicine, leading to increased internal osmotic pressure in a vesicle. (B) Osmolarity of a bicine solution (containing 10 mM HPTS, 0.2 M Na-bicine, and 0.1 M H2O2) before and after 20 min of illumination. Error bars show s.d. (n = 3). (C) Proposed radical-mediated oxidation products of bicine: diethanolamine, formic acid, and bicarbonate. (D) Mass spectrometry of a bicine solution before (left) and after (right) illumination (ESI-MS in positive mode; bicine at m/z 186.0, diethanolamine at m/z 106.2).