5 ms·
Extract the DNA. Do X-ray scattering and crystallographic studies, which would clear this issue up nicely.
by kayhi 16y ago
Extract the DNA. Do X-ray scattering and crystallographic studies, which would clear this issue up nicely.
- bhickey 16y agoWhat 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.
- lisper 16y agoYou don't want X-ray scattering crystallography, you want elemental spectroscopy.
- fnl 16y agoCrystallographic studies? What is wrong with simply doing the gradient suggested by two commenters in the blog entry? If that turns up negative, you can immediately get an answer and scrap the whole paper. (Which in itself leads to quite some speculations...) Anyway, if the calculations and assertions made in the blog (and the commenters) turn out to be correct, this will be a big black eye for Science (the journal...) for publishing this.
- kayhi 16y agoThere are quite a few biophysical techniques that could be done such as AUC, spectroscopy, scattering and crystallography. The facilities and equipment would play a role in which to pursue. The experiment I am suggesting is not very complicated, but of course depends on people's backgrounds.