high resolution Mass spec is such a shitty technique and is completely non-quantitative. How do you know that arsenic isn't associated with, say, a protein that makes the DNA resistant to being taken apart chemically. I will believe this result when they stain the DNA and run samples of the DNA down a density gradient ultracentrifugation and show that arsenic content in the media correlates with increased density of DNA, as you would expect if the arsenic is replacing phosphorus. If you don't know what i'm talking about, it's this classical experiment:
Here is my personal scientific experience speaking: If you see it everywhere, then it's likely to be an artefact. Clean up your technique, clean your instruments, and go back to an old school technique. Remember how the physicists who discovered CMB cleaned out the pigeon scat from their microwave horn telescope before they started to believe what they saw.
http://en.wikipedia.org/wiki/Semiconservative_replication#Bi...
Here is my personal scientific experience speaking: If you see it everywhere, then it's likely to be an artefact. Clean up your technique, clean your instruments, and go back to an old school technique. Remember how the physicists who discovered CMB cleaned out the pigeon scat from their microwave horn telescope before they started to believe what they saw.