Scientists first questioned whether life could store information using other chemical groups than A, C, G and T in the 1960s. But it wasn’t until 1989 that Steven Benner, coaxed modified forms of cytosine (C) and guanine (G) into DNA molecules. In test-tube reactions, strands made of these “funny letters”, as Benner calls them, copied themselves and encoded RNA and proteins.
The bases engineered by Romesberg’s team are more alien, bearing little chemical resemblance to the four natural ones. In a 2008 paper, and in follow-up experiments, the group reported efforts to pair chemicals together from a list of 60 candidates and screen the 3,600 resulting combinations. They identified a pair of bases, known as d5SICS and dNaM, that looked promising. In particular, the molecules had to be compatible with the enzymatic machinery that copies and translates DNA.
Via Marko Dolinar