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Quiz-2
1. What kind of bonds are involved in primary structure of proteins?
2. What kinds of bonds are involved in secondary structure of proteins?
3.
What are the forces that stabilize the tertiary structure of a protein?
4. What is the difference between the cross-linking of keratin in hair and that of
collagens fibrils in connective tissue?
5. The helical structure in collagen is very compact. What is the structural
explanation for this phenomenon?
6. What were the two physical criterion used by Ramchandran to predict allowed
conformations?
7. Ramchandran’s plot for poly-glycine shows four big squares of allowed
conformations which is very different from any polypeptide. Explain why?
8. Find out the primary structure of the peptide based on the information provided
below.
a) Amino acid composition: Arg-1, Lys-2, Gly-3, Tyr-2, Thr-3, Met-1, Ala-2
b) Dansyl chloride reaction result: Met-Dansyl derivative
c) Trypsin digestion yields three fragments:
i) Met-Gly-Ala-Arg,
ii) Tyr-Thr-Thr-Lys,
iii) Ala-Gly-Thr-Gly-lys
d) Chymotrypsin digestion yields three peptides;
i) Met-Gly-Ala-Arg-Tyr
ii)
Thr-Gly-lys
iii)
Thr-Thr-Lys-Ala-gly-Tyr
9. Primary structure of cytochrome c from tissue sample of unknown species was
compared to some of the known species. Based on the following results describe
the evolutionary relationship of the unknown species to the known one.
No of AA changed
Known species
2
Donkey
0
Sheep
12
Penguin
0
Cow
11
Man
10. Wool and silk are both composed of fibrous proteins, wool can stretch and shrink
but silk cannot. What is the molecular basis for this different character?
11. MALDI Mass spectrometric analysis of proteins following trypsin digestion is
very useful in the identification of proteins. Can you identify a novel protein by
this method? Explain your answer.
12. How many amino acids are found in b turn?
13. What weak interactions contribute to the close packing and stability of
myoglobin?
14. What is the advantage of NMR for protein structure determination over X-ray
crystallography?
15. A protein spot was typsin digested and the digested fragments were subjected to
electryspray MS-MS analysis. One trypsin digested fragment was subjected to Ar
bombardment and the fragments were put through the next mass spectrometer.
From the given pattern of molecular masses find out the sequence of the peptide
fragment.