It would have been nice if the author would have at least acknowledged that in reality they are nucleobases and not tiny, tiny letters curled up in our cell nuclei. Sure, 6-amino-5-nitro-2(1H)-pyridone and 2-amino-imidazo[1,2-a]-1,3,5-triazin-4(8H)one doesn't say much to us laymen, but just saying letters and not mentioning once what they stand for is really poor reporting.
I suppose the heading and maybe opening paragraph could be seen to give that impression, but the article makes note of the fact these are new nucleotides numerous times throughout the article. I found that pretty sufficient for showing that there are not in fact actual letters in DNA.
