The role of singlet oxygen and hydroxyl radical in the photobleaching of meso-substituted cationic pyridyl porphyrins in the presence of folic acid oleh Lusine Mkrtchyan, Torgom Seferyan, Marina Parkhats, Sergei Lepeshkevich, Boris Dzhagarov, Gagik Shmavonyan, Elena Tuchina, Valery Tuchin, Grigor Gyulkhandanyan