Slide 14 of 16
Notes:
Even in water, exchanging, labile protons are only observable if their exchange is slow on the NMR time scale (chemical time scale). Effectively that means that the exchange rate needs to be < 1000 min-1. In practice, kintr exchange rates of backbone and sidechain amides (Asn, Gln, Trp, Arg, Lys) become sufficiently slow at room temperature ( and below) and slightly acidic pH . All other labile protons exchange too fast over the entire pH range to be observed, unless specific unusual circumstances significantly reduce the exchange rates.
But why is the observation still limited to slow exchange?
Can we observe labile protons/ exchanging protons in slow or medium exchange? In the absence of presaturation?
