The photoionization of alkylphenothiazine (AP= alkylphenothiazine) in vesicles were observed by electron spin resonance (ESR) and electron spin echo modulation (ESEM) methods. Alkylphenothiazine derivatives including sodium 10-methylphenothiazinesulfonate (ClPS03Na), sodium 10-dodecylphenothiazinesulfonate (Ci2PS03Na), sodium 3 4 10'- phenothiaziny1) propane-1-sulfonate (PC3S03Na), sodium 6 4 10'-phenothiaziny1) ...