Question

Indicate two psi angles that are obviously unacceptable in a normal protein structure(except for linkages with Gly&Pro), and explain with Newman projections

Answer 1

the protein structure has the covalent links between the two amino acids. the rotation of protein molecule is possible in 20 different kinds of amino acids. The peptide bonds connects the carbonyl C of the amino acid to the amine N of the amino acid. the amide bond (C-N) has double bond character. the lone pairs of the nitrogen atom delocalisesto the carbonyl carbon, yaht it has some double bond character, the electrons moves towards the electronegative oxygen atom. then this structure becomes plannar, the peptide bond carbonyl and N atom and the other groups attached to it. then the hybridisation of C-N bond will become SP² AND WE KNOW THE ANGLE OF sp2 =120⁰. this 6 atoms roattes in different ways and the angle of such rotations are termed as psi angle, which are in between 120⁰ to 180^0.