And so what that means is this will be neutral. And finally this N group will be negatively charged, because the PKA of this is below the PH of seven. So we have a negative charge. And finally, if we add these charges up, we'll see that our charge, the net charge in this particular case, is zero. And so this can basically be used to find what the actual pi value of this protein is. And we'll do that in just a moment.