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
At what pH?
read about the two tautomers here.
http://www.absoluteastronomy.com/topics/Histidine