Secondary Structure

Question 1

What is a special feature of prolines?

Answer 1

Hydrophilic character as carbonyl has higher partial charge as side chain pushes more electron density onto it.

Question 2

Where are uncharged polar groups found?

Answer 2

On protein surface but can be found in interior (establishing H bonds with other groups).

Question 3

What are collagen and silk examples of?

Answer 3

Collagen = parallel 3x HELIX - repeating Pro-hydroxyPro-Gly units.

Silk = B-Sheet fibrous protein - Gly-Ala repeats form anti parallel beta sheet.

Both are fibrous proteins. I

Question 4

What is the energy of a typical H bond?

Answer 4

15-20 kJ mol-1

Question 5

Why don’t H bonds make a large contribution to protein structure?

Answer 5

H bonds in secondary structure replace those made with water.

I.e. They compensate as H bonds Witt water are lost as the water is excluded from the interface of secondary structure elements.

Question 6

What is the typical energy of an electrostatic interaction?

Answer 6

For a typical ion pair COO- and NH3+ of Lys separated by 4A in medium of E = 4

-86kJ mol-1