Which of the nitrogenof histidine is first protonated ?

When the imidazole ring of Histidine is protonated, tendency of nitrogen to be protonated (proton migrates from -COOH) is in the order

Which of the following has highest proton affinity?

Which numbered nitrogen atom gets protonated first at relatively higher pH in the following

Which numbered nitrogen atom gets protonated first at relatively higher pH in the following

Which of the following substance has highest proton affinity ?

Number of Nitrogen atoms in histidine ?

Which one of the following is not a protonic acid -