1. “ CO-R-N ” clockwise When viewing down from H to C-alpha  L-amino acid Proteins are built from 20 kinds of alpha-amino acids. 21 st aa = selenocysteine

3. Free -SH group of cysteine: -Reacts readily with heavy metals -Easily oxidized S S

5. pKa Three- and one-letter codes for amino acids

7. Insulin sequence Disulfide bond

8. Modified amino acid residues

9. Peptide unit: -Rigid -Usually trans -Dipole moment H Rotation around this C-N bond is not free.

10. These two bonds are free to rotate.

11. Alpha-helix has a large dipole moment. 0.5- 0.5+

13. Antiparallel beta-sheet Collagen sequence Proteins: -Fibrous proteins eg. keratin, collagen, silk -Globular proteins

14. G, Gly Collagen triple helix

16. Myoglobin is rich in alpha-helices.

17. Ribonuclease: beta and alpha 4 disulfide bonds

18. Beta-alpha-beta motif: The crossover connection is nearly always right- handed. Hemoglobin: tetramer Poliovirus: 60-mer

19. Antibody light chain: beta-sandwich Ribonuclease sequence

20. Proteins can be easily denatured. Refolding of proteins is very difficult.

22. Conformational change is important for function.