L4

Question 1

How did Christian Alfinsen’s experiments show that under appropriate conditions, protein folding/unfolding is reversible?

Answer 1

Treated protein with urea and b-mercaptoethanol and it lost enzyme activity so protein lost all native structure. Dialyze away urea and bME and let it oxidise and activity returned. Proteins fold first the disulphides form.

Did not work when he oxidised in the presence of urea as it gave ‘mixed’ disulfides (scrambled)

Question 2

How do protein folding chaperones help proteins avoid misfolding in the cell?

Answer 2

They bind to temp. exposed hydrophobic regions to prevent them interacting with the wrong partners.

Question 3

What is the thermodynamic basis of the hydrophobic interaction?

Answer 3

Driven by entropy as a folded protein causes burial of non polar side chains and many ‘ordered’ water molecules are released. AKA the hydrophobic effect.

Question 4

Order of electroneg

Answer 4

O>N>C>S>H

Question 5

Draw VDW interaction graph

Answer 5

Lecture 4 slie