1 B57 2,6-diamino-5-nitropyrimidin-4(3h)-one 1.000 2 B53 2,6-diamino-5-nitrosopyrimidin-4(3h)-one 0.917 3 680 6-methylamino-5-nitroisocytosine 0.786 4 5NU 5-nitrouracil 0.769 5 7VJ 2-amino-6-(methylamino)-5-nitrosopyrimidin-4(3h)-one 0.714