Amino acid and peptide conjugates of protoporphyrin: preparation and analysis by high-performance liquid chromatography,high-performance liquid chromatography/electrospray ionization mass spectrometry and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Amino acid and peptide conjugates of protoporphyrin have been prepared by reacting protoporphyringen with cysteine, glutathione and peptides containing a free thiol group under acidic conditions. The conjugates were formed by the addition of the thioamino acids or peptides to the vinyl groups of protoporphyrin during the autoxidation of protoporphyinogen to protoporphyrin and is free-radical-mediated. The conjugates were separated by high-performance liquid chromatography (HPLC) and characterized by HPLC/electrospray ionization mass spectrometry (HPLC/ESI-MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). All the conjugates formed were diconjugates consisting of diastereoisomers.