15 ms·
What would you expect to see in crystallography? A different pitch and radius on the helix? If that is the case, then assuming there is arsenic in the DNA: how
by bhickey 16y ago
What would you expect to see in crystallography? A different pitch and radius on the helix?
If that is the case, then assuming there is arsenic in the DNA: how did they manage to PCR it? I would expect it to wreck havoc with the polymerase.
- kayhi 16y agoThe first experiment would be to determine if Arsenic is present. A quite direct experiment would be to take advantage of the anomalous scattering of As vs. P by using a tunable X-ray source (synchrotron). By using a wavelength of just over 1 Angstrom As will be quite distinct from P. I would expect the radius and pitch not be drastically influenced. However, three dimensional structural prediction is quite difficult and it feels a bit uncomfortable speculating.
- timr 16y agoIf the number of arsenic atoms incorporated are as few as the molarity calculations indicate (i.e. ~1 per 5kb), I doubt that x-ray experiments would be definitive. And they're hard to do. At any rate, you'd have to extract and crystallize a fragment of DNA that was particularly enriched for As, which would necessitate most of the other controls that people are suggesting anyway. You'd probably have a pretty good confirmation/refutation of the paper's claims by the time you were set up to shoot x-rays at a crystal.
- shadowpwner 16y agoWhy would arsenic wreak havoc on the polymerase?
- sandipc 16y agoI'm guessing that this just refers to the altered As-DNA structure causing major problems with binding of the enzyme to the DNA.
- kayhi 16y agoMy apologies if my comment implies that As creates an issue with the polymerase. I would guess that it doesn't since amplifying the sequence was successful.
- bhickey 16y agoMy fault -- I implied it. I would guess that it doesn't since amplifying the sequence was successful. Or the sequence doesn't contain (enough) arsenate.