 After alanine and glycine, there are more complicated structures, even if we stay with the hydrophobic ones. So this is valine, I think. So just as we have names for those torsions, that we call them chi1, chi2, chi3, etc. in the side chain, as I'm moving out from the C-alpha, can you imagine what I would call the second carbon in the side chain here? That's right, C-beta. And in this particular case, I have two of them, and that would mean that I call them C-gamma1 and C-gamma2. If I had a fourth one here, it would be C-delta, C-epsilon, etc. So we use letters in the Greek alphabet to name the carbons, while we use this chi1, chi2, chi3 to name the torsion angles involved in those carbons. This is important occasionally when you want to do computer simulations and when you want to refer to specific atoms, or just looking at a structure and being able to refer to specific atoms. But we're not going to do that that much in this class, but you should be aware of it.