Protein X is an all helical protein with 100 amino acids including 2 cysteines and a pI of 7.0. Which one of the following graphs best describes the solubility of this protein under different ammonium sulphate (salt) concentrations?
Explanation-
Low salt → increases solubility (salting-in)
High salt → decreases solubility (salting-out)
First salting-in, then salting-out.
Resulting curve: first rises, then falls → bell-shaped, as in Option b
pH = pI = 7.0
The protein has no net charge, hence it's least soluble at pI. Salting-in effect is limited around pI but still occurs with low salt. Eventually, at very high salt, water is stripped, and protein precipitates (salting-out).
Final answer : Option b
The Ramachandran plot graphically shows which combination of torsional angles phi (φ) and psi (ψ) of amino acid residues contained in a peptide are possible. Examination of the plot below shows that only certain regions of the conformational space are permissible.
Why are all the theoretical combinations of φ and ψ not possible?
Protein X is an all helical protein with 100 amino acids including 2 cysteines and a pI of 7.0. Which one of the following graphs best describes the solubility of this protein under different ammonium sulphate (salt) concentrations?
Some cells possess peptides which contain D- form amino acids. How do they arise?
How many hydrogen bonds involving the backbone CO and NH can be observed in an α-helix consisting of 15 amino acid residues?
The regions of phi space occupied by well-characterized protein secondary structures are marked on a Ramachandran plot as shown above. Which of the following statements is CORRECT?
Which one of the following is NOT CORRECT in the context of protein structure and folding?
The following statements were made to describe a typical collagen structure.
A. Collagen has a triple-helical domain structure which consists of three distinct α-chains.
B. The collagen triple helix is stabilized by isoprenyl bonds.
C. Each α-chain has a left-handed polyproline II-type helix.
D. Each α-chain is composed of multiple triplet sequences of Gly–Y–Z in which Y is commonly proline and Z is usually hydroxyproline.
Which one of the following options has all correct statement?
Three strands of a beta-sheet of 4 peptides are hydrogen bonded with the orientation of the strands (parallel or antiparallel denoted by the arrowheads) as shown in the figure. Each strand consists of identical residues, where N and C represent terminal residues of the peptide. The three strands of each peptide are linked by amino acid sequences of the smallest length possible.
Which one of the following options is correct regarding the length of the peptides 1 to 4?
A novel organism synthesizes proteins using ribosomes from the C-terminal end to the N-terminal end rather than the usual direction (N- to C-terminus). Which main chain atom will be the nucleophile for the reaction to form peptide bonds?
Which one of the following techniques can identify acetylation on a lysine residue of a protein?
