試題詳解

19. All are important functional groups participating in H-bond formation EXCEPT:
(A) amino group of the cytosine, adenine and guanine.
(B) the ring nitrogens at position 3 of pyrimidines and 1 of purines.
(C) the electronegative oxygen atoms.
(D) the electron density in the double bonds of the bases.
(E) the carbony! group at position 4 of uracil and thymine, position 2 of cytosine, and position6 of guanine.