1. 
   Protoporphyrin
   Protoporphyrins are tetrapyrroles containing the following side chains: Protoporphyrin IX is a biochemically widely used carrier molecule for divalent cations. Together with iron (Fe 2+) the body of the heme- group of hemoglobin, myoglobin and many other heme-containing enzymes like cytochrome c an...
   Found op http://en.wikipedia.org/wiki/Protoporphyrin
   
   
2. 
   protoporphyrin
   Porphyrin ring structure lacking metal ions. The most abundant is protoporphyrin IX, the immediate precursor of haem.
   Found op http://www.encyclo.co.uk/visitor-contributions.php
   
   
3. 
   protoporphyrin
   <biochemistry> Porphyrin ring structure lacking metal ions. The most abundant is protoporphyrin IX, the immediate precursor of hem. ... (18 Nov 1997) ...
   Found op http://www.mondofacto.com/facts/dictionary?protoporphyrin
   
   
4. 
   protoporphyrin
   (pro″to-por´fә-rin) a porphyrin whose iron complex united with protein occurs in hemoglobin, myoglobin, and certain respiratory pigments. It is accumulated and excreted excessively in the feces in erythropoietic protoporphyria and variegate porphyria.
   Found op http://www.encyclo.co.uk/local/21001
   
   

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