Lecture 7

Question 1

1) What is the problem with acid and base hydrolysis? Which one is better?

Answer 1

• acid converts glutamine and asparagine to acid, destroyes trp, cys
• base destroyes Ser, Thr, Cys and makes racemic mixtures.
  Acid better because it is less destructive.

Question 2

2) What does Ninhydrin do?

What does Edman’s reagent do?

Answer 2

• Stains AA’s blue except proline is yellow

- Label amino acids

Question 3

3) What experiments are done to find where the N-terminal residue? What do they test for?

Answer 3

• End group analysis: use different reagents that react with the terminal- amine group, give different colors, Eg: Sangers and Dansyl reagants.

Question 4

4) What does Edman’s Degration do? What do we have to do about cystine residues?

Answer 4

Label’s N-terminus residue and cleaves residues one by one. Cystine disulphide bonds must be cleaved first.

Question 5

5) What are some protein sequencing strategies? Give some examples of cleaving proteins.

Answer 5

Cleave proteins, break disulphide bonds, purify fragments.

Examples are Proteases, crynobromide, etc.

Question 6

6) What are 6 important things we learn from amino acid sequences?

Answer 6

• allows us to compare new sequences with others to assert similiarities within proteins
• comparison of sequences of proteins to compare evolutionary pathways.
• searched for evidence of internal repeats
• many proteins contain signal sequences
• allows antibodies to be prepared against specific proteins
• synthesis of DNA probes