And so this is a positively charged amino acid, and that is found in a very low PH, in a PH of around one. Now, in the middle, we have this zvitarion form. And at this end, when we are above a PH of nine, when it's very basic, we have a negatively charged species, as shown in the following diagram. Now, the final thing that I'd like to mention about amino acids is so amino acids essentially are the same on this group, on this group, and on this group. Now, where we can differentiate one amino acid from another is by the R group, by that side chain. So we have different types of side chains.