#Question id: 711
#Part-B Specialized Branches in Biotechnology
The shortest alpha helix segment in a protein that will span a membrane bilayer has about.
#Question id: 713
#Part-B Specialized Branches in Biotechnology
Which of the following polypeptides is most likely to form an α helix?
#Question id: 717
#Part-B Specialized Branches in Biotechnology
What is Φ & Ψ angles for collagen triple helix?
#Question id: 719
#Part-B Specialized Branches in Biotechnology
Suppose that a 40-residue segment of a protein folds into a two-stranded antiparallel β structure with a 4-residue hairpin turn. What is the longest dimension of this motif?
#Question id: 721
#Part-B Specialized Branches in Biotechnology
Addition of urea leads to a two-state transition between α-helix and random coil conformation. It has been observed that [θ]222 of the polypeptide is -11000 deg cm2 dmol-1 in the presence of 6M urea. Initially it was observed that tile values of mean residue ellipticity at 220 nm ([θ]220) are -36000, and +4000 deg cm2 dmol-1 for α-helix, and random coil conformations of this polypeptide. The percentage of the polypeptide in α-helix conformation is:
#Question id: 723
#Part-B Specialized Branches in Biotechnology
Common structural elements in proteins such as α-helices or β-sheets are characterized by uniformly repeating, energetically favorable main chain conformations which additionally exhibit a completely saturated hydrogen-bonding network of the main chain NH and CO groups. Although polyproline or polyglycine type II helices (PPII or PGII ) are frequently found in proteins, they are not considered as equivalent secondary structure elements. Which of the following statements are correct about PP and PGs.
A. PGII -like helices form hexagonal bundles which appear to fulfill the criterion of a (largely) saturated hydrogen-bonding network of the main-chain groups
B. main chain NH and CO groups of the central PGII -helix are saturated by either intra- or intermolecular hydrogen-bonds, resulting in a self-contained hydrogen-bonding network
C. The formation of the right-handed PPI helix is possible only with proline residues because of the required cis conformation.
D. PPII helices seem to be stabilized by main chain-water hydrogen bonds (in the absence of main chain- main chain H-bonds), and tend to have a regular pattern of hydrogen bonds with water. After this, it is not surprising, that PPII helices are found mostly on the protein surface.