Protein structure [20 pts]. The biphenyl group adopts a ground state conformatio

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Protein structure [20 pts]. The biphenyl group adopts a ground state conformation that is twisted around the central C-C bond, with a torsion angle () of ~45 in the gas phase and ~20 in aqueous solution

1) Protein structure [20 pts]. The biphenyl group adopts a ground state conformation that is twisted around the central C-C bond, with a torsion angle (D) of 45 in the gas phase and -20° in aqueous solution. P angle btwn 1-2 and 3-4 4 0 for planar conformation a) 110 pts In 2-3 sentences, briefly explain why the most stable ground state conformation is twisted. You should consider steric and electronic factors, and it might help to consider the limiting cases (0o and 90°) b) [10 pts The Baker and Schultz groups designed a set of proteins that twist the biphenyl group into unusual conformations. Download the pdb files AS02 and 4S03 and measure the torsion angle (D) for the biphenyl group at residue 11. Report your answer to the tenths place. PDB Torsion angle (D) 4S02 4S03 There are multiple equivalent ways to define the torsion angle depending on exactly which carbon atoms you pick. Any of the equivalent answers will be accepted.

Explanation / Answer

a) Ideally the considering the electronic factors of an aromatic compounds the torsion angle should be zero as both the phenyl groups are planar. but due to the steric hindrance of ortho H atoms (at positions 1 and 4 in given figure) the plans of two phenyl groups are slightly twisted depending on the bulkiness of the group present at ortho position. when we replace the H atoms with bulkier groups like methyl -CH3 and carboxylic -COOH the torsion angle further increases in order to accommodate these groups without any steric hindrance and electronic repulsive factors.

b) Please provide the pdf files to answer this question.

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