So that's exactly why valine is more electronegative than Alanine and so forth. Now, what distinguishes Leucine from isolucine? Well, it's the fact that this carbon here contains this methyl group, and that makes this carbon a chiral carbon. So this is chiral, and that means it contains a mirror image. Now, inside the proteins of our body, this is the only nantomer of isolucine that we actually find when this H atom is coming out of the board, as shown in the following diagram. Now, let's move on to methionine.