The cysteine has a PKA of 8.3, and below 8.3, this will be protonated. And so it will not have a charge. So we have a charge of zero. And finally, last but not least, this alpha carboxyl group that has a PK value of 3.1. So what this means is below a PH of 3.1, this group will be protonated. And so this will have a charge of zero.