True or false? Poly aspartate is unlikely to form an alpha helix at pH 2.8 Hydro

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True or false? Poly aspartate is unlikely to form an alpha helix at pH 2.8 Hydrophobic interactions promote protein folding in aqueous solution because the number of ordered water molecules surrounding the folded proteins is maximized. p-turns will be found in parallel, but not antiparallel ß-sheets Asparagine's and glutamine's side chains do not ionize in aqueous solution, but both side chains can participate in hydrogen bonding interactions. In a globular protein, the hydrophobic amino acid side chains are mostly buried in the interior of the molecule. Hydrogen bonds between carbonyl oxygens and hydrogen atoms covalently bonded to carbons in adjacent peptides contribute to the stabilization of B-sheets Submit Answer Tries 0/99 Post Discussion Send Feedback

Explanation / Answer

Answers:

Explanation:

1. Aspartate has a Carboxylate group on its side chain which is in close vicinity to the -carbon bound amine group. Due to this the side chain Carboxylate competes for hydrogen bonding with the Back bone atoms. This disrupts the formation of -helix which requires formation of intra-chain Hydrogen bonds between 'O' of Carbonyl group and 'H' of Amine group on the back bone. Because of this Aspartates have very little tendency to form -helices. pKa of side chain carboxylic acid on aspartate is 3.65. At pH 2.8, as pH < pKa, the carboxylic acid group remains protonated.

Carboxylic acid group can interfere with intra chain hydrogen bonding as a Hydrogen acceptor when deprotonated and Hydrogen donor when protonated. Either way Asparates have very little tendency to form alpha helix structure.

2. Protein folding is a phenomenon that occurs to promote formation of energetically stabler structural conformation. In aqueous environment, Hydrophobic (water hating) amino acid residues, when they interact with surrounding water molecules lead to a higher energy, unstable system. Thus the hydrophobic interactions cluster the hydrophobic amino acids and expose Hydrophilic (water loving) amino acids to form hydrogen bonds with the surrounding water molecules. This H-bond interactions lead a very ordered arrangement of Water molecules around the protein to form a layer of 'Water of Solvation'.

3. Beta-turn leads to sudden change in the direction of the polypeptide chain. This change in direction is seen in Anti-parallel Beta sheets rather than Parallel Beta sheets.

4. Asparagine and Glutamine have an Amide group in their side chain. Amide group (CONH2) doesnot ionize but it has a weak dipole that can allow it to participate in H-bonding.

5. Hydrophobic amino acids owing to their nature to stay away from water, tend to cluster together in the core of a globular protein, while hydrophilic amino acids are exposed to interact with surrounding water molecules.

6. Hydrogen bonds between backbone Carbonyl Oxygens (C=O) and backbone Amine Hydrogens     (N-H) are primarily critical for keeping the Beta Sheet stable and not Hydrogens covalently bound to Carbons.

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