When the base pair A=T in the middle of a short (20 nucleotide) synthetic duplex DNA strand was replaced with a. Z F base pair (shown below) the duplex was destabilized by about 13.4 kJ/mol.
However, when the pair was at the end of the strand it was in fact more stabilizing than A=T.
Explain these results in light of weak forces responsible for the DNA double helix.
