Fibrous proteins

Question 1

What’s the structure of collagen and how does this influence its characteristics?

Answer 1

Gly-X-Y repeating unit allows peptide chains = contribute to sharp twisting of LH helix

• Gly: sml = fit in interior of helix
• X: Pro*
• Y: 4-Hydroxyproline*
• can be another AA

Question 2

List at least three differences between globular and fibrous proteins?

Answer 2

Globular: Spherical; Hydrophobic res. in interior; soluble in H2O
Fibrous: Long strands; Lots of hydrophobic res.; insoluble in H2O

Question 3

DIstinguish between α-chain of collagen, α-helix, and α-keratin?

Answer 3

• α-chain: LH helix
• α-helix: RH helix
• α-keratin: Fibrous protein in hair, skin, horns, nails

Question 4

In perming hair, what protein is affected and how is the ‘perm’ effect achieved?

Answer 4

Disulphide bonds broken in b/w α-keratin filament alter shape of hair strands.

1. hair is reduced = break disulphide bonds
2. curl = alter shape
3. hair is oxidised = disulphide bond forms to fit new shape

Question 5

How is fibroin structure different from collagen and α-keratin?

Answer 5

Fibroin: close packing of β-sheets

Collagen & α-keratin: tight packing helixes

Question 6

How is elastin elastic and fibroin is not?

Answer 6

• Elastic: microfibril -> globules can be stretched. And is held by covalent desmosine bond
• Fibroin: non-covalent interactions

Question 7

Explain using your knowledge of protein structure why silk is flexible but does not stretch very much

Answer 7

B-sheets held tog. by non-covalent interactions. B-sheet regions don’t stretch

Question 8

What are some of the biotechnology applications of fibroin?

Answer 8

• Clothing industry
• Sporting industry (sail cloth etc)
• mdeical industry: scaffolds
• Pharmaceutical industry: fibroin derived nanopart. for drug delivery