Arginine, just like Lysine, also contains this relatively long side chain group. But instead of having this primary amino group, the group here is known as the guanidinium group. And the guanidinium group has an even higher PKA value. 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.