Arsenic and Phosphorus

February 11, 2011

There is currently a debate going on whether arsenic could replace certain functions which normally phosphorus fulfills. This effect was first described in a bacterium from Mono Lake (Wolfe-Simon, Science, 2010). Now a publication sheds some light on the probability of this phenomenon when it comes to the incorporation of arsenic into DNA molecules instead of phosphorus (Fig. 1). In a publication in ACS  Chemical Biology three scientists now calculated the half-live time an arsenodiester linkage within the DNA backbone needs to dissolve in 25°C water and compared this to the half-life time a standard phosphodiester linkage needs to dissolve under the same conditions.

Fig. 1: Standard DNA has a half-life time of approximately 300,000 years. For DNA which contains arsenodiester linkages this time is much lower: o.06 seconds (1).

Yet this is not impossible: DNA could be present in a dehydrated state, for example the DNA molecules could potentially be shielded by proteins or other small molecular compounds. In addition very fast repair mechanisms could make arsenic containing DNA possible.

(1) Fekry, ACS Chem. Biol., 2011