▁The ▁difference ▁to ▁free ▁FM N ▁is ▁even ▁more ▁significant ▁in ▁the ▁case ▁of ▁the ▁phot ost ab ail ity , ▁the ▁prote ins ▁resistance ▁to ▁ble ach ▁out ▁during ▁prolong ed ▁and ▁inten se ▁ir rad iation ▁with ▁blue ▁light . ▁Based ▁on ▁the ▁ble aching - hal ft ime ▁( the ▁times ▁it ▁takes ▁to ▁reduce ▁the ▁initial ▁flu ores c ence ▁intensity ▁to ▁ 5 0 % ▁upon ▁ill um ination ) ▁the ▁gen et ically ▁engine ered ▁variant ▁ph i LO V 2 . 1 ▁is ▁approximately ▁ 4 0 x ▁as ▁stable ▁as ▁free ▁FM N . ▁This ▁stabil izing ▁effect ▁can ▁be ▁observed ▁for ▁almost ▁all ▁F b FP s , ▁although ▁it ▁is ▁usually ▁in ▁the ▁range ▁of ▁ 5 x ▁- ▁ 1 0 x . ▁The ▁average ▁flu ores c ence ▁lifetime ▁of ▁F b FP s ▁is ▁in ▁the ▁range ▁of ▁ 3 . 1 7 ▁( P p 2 F b FP ) ▁and ▁ 5 . 7 ▁ns ▁( e . g . ▁E c F b FP ). ▁They ▁are ▁thereby ▁much ▁longer ▁than ▁the ▁ones ▁of ▁G FP ▁derivatives , ▁which ▁are ▁usually ▁between ▁ 1 , 5 ▁and ▁ 3 ▁ns . ▁ ▁F b FP s ▁are ▁therefore ▁well ▁su ited ▁as ▁don or ▁domains ▁in ▁För ster ▁reson ance ▁energy ▁transfer ▁( F RE T ) ▁systems ▁in ▁conj unction ▁with ▁G FP ▁derivatives ▁like ▁Y FP ▁as ▁accept or ▁domains . ▁ ▁Adv antages ▁and