This is equal to a PKA of 12.5. And what that means is all of these side chain groups, for all of these arginine at the normal physiological PH of seven, will be protein, will have a full positive charge. Now, unlike in this case, in this case, the positive charge is delocalized among different atoms, and that stabilizes this molecule. So this molecule is, in fact, resonant stabilized. And finally, let's look at histidine. Now, we saw that Lysine and Arginine are always positively charged at the physiological PH of around seven.