#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.
#Question id: 731
#Unit 1. Structure and Function of Biomolecules
Which of the following structure is mentioned in the given Ramachandran plot
#Question id: 732
#Unit 1. Structure and Function of Biomolecules
Ramachandran plots can help increase the accuracy of models derived from x-ray crystallography data. The plot below was created by measuring phi, and psi for each amino acid residue in a 2.2 A resolution crystal structure. In the plot, which excludes Gly and Pro residues, selected residues (dots) are numbered 1 through 5.
Which of the following statements can be correctly stated for this plot in reference to selected residues?
A. Residues 1 and 3 are in either B sheets
B. residue 2 is in a right-handed a helix, and residue 4 is in a left-handed a helix.
C. If residue 5 were Gly, it might be in an acceptable position in the plot