3. 3-Dimensional Structure of Proteins

8. 4 levels of protein structure:

9. Alpha Helix Common structure: ~25% of all amino acid residues! (hair…) Optimal use of internal hydrogen bonding: 1st -4th Alpha-helices are generally right handed

11. 1 2 3 4 5 6 7

12. Interactions of R groups with dipole: Stabilizes or destabilizes the alpha helix Alpha helices have an intrinsic dipole: 3 constraints affect stability of alpha helix: 1)interactions between adjacent R groups steric electrostatic 2) Occurrence of Pro and Gly 3) interactions between AAs at end of helix and intrinsic dipole

14. Characteristics of alpha helices: Not limited to coiled-coils!! Common structural units

18. Proteins can have mostly alpha helix, beta sheet, or both Other secondary structures also exist! (tomorrow…)