1. Lecture 5 Web: pollev.com/ucibio Text: To: 37607
Type in: <your question>

2. Lecture 5 objectives
Be able to design experiments to answer scientific questions
Understand Anfinsen’s experiment; derive conclusions from data
Understand why peptide bond angles are rotationally constrained
Understand how rotational constraints lead to 2° structure
Know the different interactions that stabilize structure

3. OK. What does this all have to do with enzymes?
Need precise 3-D structure
Protein made of amino acids
R-groups have different interactions
Connect R-groups/amino acids  Protein structure

4. The scientific method…
I think “X” BECAUSE “Y”
Design an experiment to PROVE “X”
Experiment: Predict outcomes if “X” is TRUE
Predict outcomes if “X” is FALSE
Do experiment, observe results
Results; Therefore “X” is TRUE/FALSE
Unexpected results/observations = Discovery!

5. OK. What does this all have to do with enzymes?
Anfinsen’s experiment
Took a protein (AP) & forced it to unfold
- Protein lost activity

6. OK. What does this all have to do with enzymes?
Anfinsen’s experiment
Took a protein (AP) & forced it to unfold
- Protein lost activity
Therefore:______________________________
Allowed protein to recover
- Over time, activity returned

7. OK. What does this all have to do with enzymes?
Anfinsen’s experiment
Took a protein (AP) & forced it to unfold
- Protein lost activity
Therefore:______________________________
Allowed protein to recover
- Over time, activity returned
Therefore:______________________________

8. What does a protein need in order to fold?
Protein folding information contained in
OK. But how does amino acid sequence “fold?”

9. Peptide bond is planar…

10. …but not bonds on either side!

11. Rotation of bonds around peptide bond

12. Peptide backbone rotation

13. “Folding” proteins Amino acids have different properties
Different preferred Psi and Phi angles
Bonds can rotate and pivot

14. Secondary structure 3D structure H-bonds between ____ & ____
____ & ____ of peptide bonds
Close together in primary structure

15. Folding into secondary structures
Bond rotation causes secondary structure

16. The a-helix: Annotate
Different parameters define a-helix

17. b-Sheet: Annotate

18. b-Sheets
Sheets can be twisted

19. Bends / Loops
Bends or Loops: Important
Structured/Unstructured

20. Tertiary structrue Bring secondary structure elements together
_____________ interactions important
Unstructured regions important

21. The a-helix
Arrangement of side chains important

22. Tertiary structure

23. Tertiary structrue Take picture
Upload to Canvas assignment “Barrel structure”