GppNHp and GTPgS are used to uncouple GPCR from G proteins. A lot of work is done by adding 10uM GppNHp to receptors expressed in cell membranes to study G protein activation leading to their uncoupling from receptors. Can this be done in intact mammalian cells? - can GppHNp be added to cell media to enter cells and uncouple receptor from G proteins? (if so, at what concentration and time duration?)