Figure 3: Product-ion spectrum of the [M+H]+ ion of A) Adenine, B) Guanine C) Thymine D) Cytosine and E) Uracil. Product-ion spectrum of the [M+H]+ ion of F) [15N]2 Adenine, G) [15N]2 Guanine H) [15N] Thymine I) [15N]2 Cytosine and J) [15N] Uracil.