a) It is known that double stranded DNA is denatured at low pH. pKa values should allow the determination of whether this is due to perturbation of the hydrogen bonding in A-T and/or G-C base pairs. The table gives values for the pKas of different protonated groups in the nucleobases. Nucleobase Position & pKa A N1, 3.5 G N7, 1.6; N1, 9.2 C N3, 4.2 T N3, 9.7 a) Draw the A-T and G-C base pairs. - Label the bases with the one-letter code. – - Number the atoms in the rings and label the atom that attaches to the sugar. - Mark the groups that interact in normal Watson-Crick base-pairing with arrows: use an arrow towards the groups for hydrogen bond acceptors, and use an arrow away from the group for hydrogen bond donors. b) Circle the nitrogen atoms that would be protonated at very low pH (pH 3) that are not protonated at pH 7. c) Will A-T, or G-C base-pairs or both kinds of base-pairs be perturbed at pH 3?
a) It is known that double stranded DNA is denatured at low pH. pKa values should
allow the determination of whether this is due to perturbation of the hydrogen bonding in A-T
and/or G-C base pairs. The table gives values for the pKas of different protonated groups in the
nucleobases.
Nucleobase Position & pKa
A N1, 3.5
G N7, 1.6; N1, 9.2
C N3, 4.2
T N3, 9.7
a) Draw the A-T and G-C base pairs.
- Label the bases with the one-letter code. –
- Number the atoms in the rings and label the atom that attaches to the sugar.
- Mark the groups that interact in normal Watson-Crick base-pairing with arrows: use an
arrow towards the groups for hydrogen bond acceptors, and use an arrow away from the
group for hydrogen bond donors.
b) Circle the nitrogen atoms that would be protonated at very low pH (pH 3) that are
not protonated at pH 7.
c) Will A-T, or G-C base-pairs or both kinds of base-pairs be perturbed at pH 3?
Trending now
This is a popular solution!
Step by step
Solved in 4 steps with 6 images
