4. No arsenic involvement in formation of high energy bonds
But there is even more direct biochemical evidence that makes impossible for arsenic to play the role of a stable component of a nucleic acid backbone in an aqueous environment. Arsenic is a poison, and this has been known for millenia. Beside involvement in oxido-reduction reactions (which can be used both to evolve arsenite into its more innocuous form arsenate, and to recover energy), arsenic can indeed replace phosphorus in many phosphorolytic reactions and even form carbohydrate arsenates that are similar to their phosphate analogs (Lagunas & Sols, 1968). However this is limited to exchange reactions that cannot lead to stable and useful compounds.
It is also possible to begin to construct compounds along the line predicted to exist if phosphorus could replace arsenic, for example by constructing an arsenical analog of adenosine diphosphate (an essential pre-requisite if the if the claims published by Science were true). While difficult, a synthesis in which the phosphono-oxy group of ADP was replaced by the arsenomethyl group (arsenate itself was far too unstable at this position, requiring replacement of the bridging oxygen by a methylene group) was achieved by Dixon and colleagues. The product was unable to compete for ADP in any of its standard substrates (Webster et al. 1978). A further demonstration puts the final nail in the coffin: the arsonomethyl analogue of AMP can be used as a substrate for adenylate kinase. It permits transfer of a phospho group from ATP, but like all anhydrides of arsonic acids breaks down immediately, transforming the enzyme into an ATPase (Adams et al. 1984). The situation would be even worse if the hypothetical arsenical analog of ATP could have existed.