#Question id: 724
#Unit 1. Structure and Function of Biomolecules
In 1988, Richardson and Richardson observed that certain amino acid residues are statically favored as the amino-terminal caps for the alpha helices in 45 globular proteins. Which of the following statement stand correct with stability of helix?
A. The introduction of a negatively charged side chain at the N-cap, which can neutralize the partial dipole created by the unpaired amide protons, has been shown to increase stability
B. In particular, Gly is often observed at the both C-cap position and N-cap positions
C. In particular, Gly is often observed at the C-cap position only
D. In particular, Gly is often observed at the C-cap position, Asn at the N-cap position, Pro at the Ncap+1 and Asp and Glu at N2 and N3
#Question id: 725
#Unit 1. Structure and Function of Biomolecules
At 25°C values of [θ]222, the mean residue ellipticity at 222 nm, are - 33,000 and -3,000 deg cm2 dmol-1 for a polypeptide existing in α- helical (α) and β-structure (β), respectively. If this polypeptide undergoes a two-state heat-induced α-β transition, and a value of [θ]222 = -15,000 deg cm2 dmol-1 is observed at 60°C, then this observation leads to the conclusion that the α helix conversion to β- structure is:
#Question id: 726
#Unit 1. Structure and Function of Biomolecules
The structure of a protein is known from X-ray diffraction studies which gave 30% - helix, 50% -sheet and 20% random coil. Circular dichroism (CD) measurements gave 50% -helix, 40% -sheet and 10% random coil. What could not be a possible explanation for these observations.
#Question id: 727
#Unit 1. Structure and Function of Biomolecules
26-residue peptide composed of alanine and leucine shows a circular dichroism (CD) spectrum characteristic of α-helix at 50°C in 5 mM phosphate buffer at pH 7.4. When the peptide solution is cooled gradually to 25°C, and the CD spectra are recorded at different temperatures, the most likely observation will be that
#Question id: 728
#Unit 1. Structure and Function of Biomolecules
Match the following tile peaks with corresponding circular dichroism spectra
| A. Alpha helix | I. negative bands at 222 nm and 208 nm and a positive one at 190 nm. |
| B. Beta sheet | II. negative band at 218 nm and a positive one at 196 nm. |
| C. Random coil | III. positive band at 212 nm and a negative one around 195 nm. |
#Question id: 729
#Unit 1. Structure and Function of Biomolecules
Which of the following is correct about the collagen triple-helix domain
a. is rich in glycine. b. is rich in proline.
c. is rich in hydroxyproline. d. is an alpha helix.