PNA-DNA Stability: Is Hybrid More or Less Stable?

[pzona]

If "unzipped" PNA and DNA combine to form a double helix, will the hybrid be more or less stable than a pure DNA double helix? This was a question on my chem homework (in a section on intermolecular forces), but I'm posting in this section as I already turned in the homework so I'm asking more out of curiosity than anything. The only real information I had on PNA was that its backbone is neutral, while I know that the phosphates in DNA give its backbone a negative (-2?) charge. I'm not sure how these really affect each other, as the base pairs are what connect the two together, but the charges seemed to be emphasized in the question, and this really confused me.

I'm not sure how common PNA (peptide nucleic acid) is, but I asked this question to some grad students in the bio lab where I work, and they weren't too sure as they hadn't worked much with PNA (a few didn't remember even learning about it actually). On my homework I guessed that it would be less stable, just because I know that DNA is pretty stable as it is, but I'm starting to think the stabilities would be about equal, and that the part about the charges was just thrown to distract me. Anyway, if anyone can even help me out with the thought process in this problem, I'd appreciate it.

 

[chemisttree]

I would say that the bonding should be stronger in PNA since all things being equal, a neutral backbone would lack charge repulsion present in both DNA and RNA. The interstrand bonding is identical to that of DNA... identical purine and pyrimidine bases are present in both classes of compounds and both form the same Watson-Crick pairs .