The thing about histidine is, even though it is basic, it bears a full positive charge on that side chain group. It can also sometimes be neutral at the physiological PH of around seven. That's because, unlike in this case, in this case, the PKA value here is around six. And what that means is histidine can exist in his protonated or deprotonated state at a neutral PH. And this really depends on what the local environment is and what the local conditions are around this amino acid. Now, this group here is known as the immediazel group, and it has a PKA of 6.0.