It is nevertheless clear, from the formulæ set out below, that the addition of a proton to the nitrogen atom of the pyrrolidine ring of the base does in fact convert this atom into a quaternary ...

This heme protein is jointly produced by the legume and bacterium; the legume produces the apoprotein while the bacterium produces the heme (porphyrin ring bound to an iron atom). Nitrogen is an ...

This image depicts the chemical structure of cytosine. It shows a hexagonal ring with nitrogen atoms at positions 1 and 3, and a primary amine group attached to carbon 4. The two remaining positions ...