2-Nitro-4-azidophenylsulfenyl-beta-endorphin 96725-48-3 Naps-beta-EP beta-Endorphin (sheep), 18-L-tyrosine-27-(1-((4-azido-2-nitrophenyl)thio)-L-tryptophan)-31-L-glutamic acid- beta-Endorphin, 2-nitro-4-azidophenylsulfenyl-