8. A polypeptide "ala-ser-val-asp-leu-gly-glu" is folded into an α-helix. Which amino acid is the carbonyl group of alanine hydrogen bonded?
(A) serine,
(B) aspartic acid,
(C) valine,
(D) leucine,
(E) glutamic acid.

A polypeptide "ala-...