Question

For the amino acid histidine, the nitrogen with the H attached to it is not basic (since you can draw out the resonance for it). But the other nitrogen that has a double bond is not basic. Why is this?? I can draw out the resonance for the double bonded nitrogen as well.. so shouldnt it be considered nonbasic as well. can someone please explain this to me? Thanks

Answer 1

At what pH?

read about the two tautomers here.

http://www.absoluteastronomy.com/topics/Histidine