Propionic acid side chain hydrogen bonding in the malaria pigment beta-hematin.
Malaria pigment, or beta-hematin, the insoluble heme detoxification product resulting from the intraerythrocitic digestion of hemoglobin by young malaria trophozoites has been structurally characterized by X-ray powder diffraction and shown to contain chains of propionic acid linked dimers. Although there is considerable spectroscopic evidence for a monodentate propionate-iron interaction in this crystalline material, the spectroscopic characterization of the propionic acid dimer is limited. Herein we demonstrate the presence of the propionic acid dimer unit by H/D isotope substitution in carboxylic acid dimer. In the Raman spectrum of the deuterium substituted compound there is a circa 12 cm(-1) shift, H: 1629 cm(-1) vs. D: 1617 cm(-1) in the symmetric ring breathing mode for the propionic acid dimer. On the other hand, the IR active asymmetric stretch has a very small shift, <3 cm(-1), upon deuteration. These, and other vibrational data, are consistent with the presence of a planar carboxylic acid dimer in the structure of beta-hematin.
Bohle
D Scott
DS
Department of Chemistry, University of Wyoming, Laramie, WY 82071-3838, USA. Bohle@uwyo.edu
Kosar
Andrew D
AD
Madsen
Sara K
SK
D000818:Animals; D018360:Crystallography, X-Ray; D019281:Dimerization; D006420:Hemeproteins / Q000737:chemistry*; D006801:Humans; D006860:Hydrogen Bonding; D016778:Malaria, Falciparum / Q000378:metabolism*; D008958:Models, Molecular; D010963:Plasmodium falciparum; D011422:Propionates / Q000737:chemistry*; D011487:Protein Conformation; D013059:Spectrum Analysis, Raman
D006420:Hemeproteins; D011422:Propionates; C020753:hemozoin; C029658:propionic acid