The conclusion that arsenic ‘substituted for’ or ‘replaced’ phosphorus in DNA was not supported by the data. One key example was fig. 2A of Wolfe-Simon et al. (2011), which shows agarose gel electrophoresis analysis with two lanes of crude nucleic acid fractions, one from bacterial cells grown on high phosphate/no added arsenate and the other from

cells grown with 40 mM arsenate/no added phosphate. However, there was a measured phosphate contamination level about 1000× less than the added arsenate. This figure has several major disqualifying problems that should have been apparent to the 12 authors and the three outside referees who were sent buy H 89 the manuscript for review. Both lanes show single tight high molecular weight bands characteristic of DNA. Arsenic content of the gel regions containing the DNA bands measured as 1.3 As atoms per 100 000 www.selleckchem.com/products/MDV3100.html C atoms under high arsenic conditions and 0.7 As per 100 000 C when grown in the absence of arsenic. That is only a twofold difference.

Importantly, the DNA was not eluted from the gel. No explanation was given as to why the DNA was not extracted, as is an easy and needed technique. Of course, the ratio of P to C in DNA is more like 1 : 10 than 1 : 100 000, but agarose gels contain about 1 mg mL−1 agarose, a seaweed polysaccharide. Seaweed products are well and long known to contain high levels of Thiamine-diphosphate kinase harmless organoarsenic compounds (e.g. arsenic in seaweed www.food.gov.uk/science/research/surveillance/fsis2004branch/fsis6104‎). My favorite, Nori, contains about 24 mg As kg−1 product, approximately the same ratio of As/C as reported by Wolfe-Simon et al. (2011). A simple negative control measuring arsenic in a region of the agarose gel without DNA would have quickly tested the hypothesis that the arsenic measured

by Wolfe-Simon et al. (2011) came from the major carbon source in the gel (agarose) and not the DNA. There are other puzzling and untested questions from fig. 2A of Wolfe-Simon et al. (2011), for example, the failure to measure the arsenic content in the massive ribosomal RNA-containing bands for the high P-/no As-grown cells. These major rRNA bands are not identified as such by Wolfe-Simon et al. (2011), but from staining intensity (not measured), they contain much larger amounts of nucleic acid than the DNA bands. If there were arsenic in nucleic acids, the amount of arsenic also should have been much larger in the RNA bands. To miss such a simple available measurement was an important failure of the authors and the reviewers. There was a NASA press conference the day Wolfe-Simon et al.