Alexander Varshavsky discovered, the half-lives of many cytoplasmic proteins vary with the identities of their N-terminal residues via the so-called N-end rule:-

A. Destabilizing N-terminal residues Asp, Arg, Leu, Lys, and Phe have half-lives of	i. Only 2 to 3 minutes,
B. Stabilizing N-terminal residues Ala, Gly, Met, Ser, Thr, and Val have half-lives of	ii. >10 hours in prokaryotes iii. >20 hours in eukaryotes.

#Question id: 721

#Unit 1. Molecules and their Interaction Relevant to Biology

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: 720

#Unit 1. Molecules and their Interaction Relevant to Biology

How would a homopolymer of alanine be more likely to form an alpha helix in water or in a hydrophobic medium?

#Question id: 719

#Unit 1. Molecules and their Interaction Relevant to Biology

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: 718

#Unit 1. Molecules and their Interaction Relevant to Biology

Poly- L -leucine in an organic solvent such as dioxane is a helical, whereas poly- L isoleucine is not. Why do these amino acids with the same number and kinds of atoms have different helix-forming tendencies?

#Question id: 717

#Unit 1. Molecules and their Interaction Relevant to Biology

What is Φ & Ψ angles for collagen triple helix?

#Question id: 716

#Unit 1. Molecules and their Interaction Relevant to Biology

In beta turns which amino acid is not allowed at i and i+3 position?