1 The following oligopeptide could predominantly form turns

1) The following oligopeptide could predominantly form turns and loopsin a protein

a)WYPTGPGSGP

b)IVLDENDDEN

c)WTAWWGSVIL

d)IVLDNPTNGI

e)WYLDAWPTEE

2) Which of the following reagent is used to cleave disulfide linkage

a) Urea

b) SDS

c) Guanidinum hydrochloride

d) Acetic acid

e) Noneof the above

3) In biological macromolecules, the following two non-polar groups most commonly participates in the formationof hydrophobic interactions

a)N-H andO-H

b)N-H andC-H

c)C-H andC-C

d)C-H andO-H

e)C-C andO-P

Need also explanation why!!

Solution

In the peptide sequences given in the question, Sequence 1 could predominantly form turns and loop this is due to the fact that these structures predominantly consist of Glycine and proline amino acids. Since the R group of glycine is H which is small and is therefore flexible and rotates easily, a property needed in these structures. Proline is due to the reason that peptide bonds involving the imino nitrogen of proline readily assume the cis configuration and this is this form (cis configuration), which is very important for a tight turn. In the sequence given in the question, the percentage of G+P is highest for sequence 1 and is 60%, therefore it could adopt turns and loop structures.

Sequence

G+P (%)

WYPTGPGSGP

60.0

IVLDENDDEN

0.0

WTAWWGSVIL

0.0

IVLDNPTNGI

20.0

WYLDAWPTEE

10.0