So the electronegativity of carbon is 2.55, and the electronegativity of sulfur is 2.58. And those values and those values are essentially the same. And that's exactly why these bonds are non polar. And so this side chain of methionine is also non polar, it's non reactive, and it's hydrophobic. Now, what about these remaining three? What exactly do Phenylalanine, Tyrosine, and tryptophan have in common?