The names of the porphyrins of interest consist of a word and a number, e.g., uroporphyrin III. The word denotes the kinds of substituents found on the ring, and the number denotes how they are arranged.
This is somewhat reminiscent of a Shakespearean sonnet, in which the rhyme scheme is ABAB CDCD EFEF GG.
This is (at the end) somewhat reminiscent of the rhyme scheme of a Petrarchan sonnet: ABBA ABBA CDE CDE.
(Animation with sound.)
If three kinds of groups are present, as in the protoporphyrins, naming can become more complicated, and the naming conventions are not altogether uniform. Heme, for example, is derived from the III series, but its immediate precursor is variously referred to as protoporphyrin III or protoporphyrin IX.
Here is a diagram of some examples of porphyrins with their correct names.
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Last modified 1/5/95