Propionic acid side chain hydrogen bonding in the malaria pigment beta-hematin |
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Authors: | Bohle D Scott Kosar Andrew D Madsen Sara K |
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Affiliation: | Department of Chemistry, University of Wyoming, Laramie, WY 82071-3838, USA. Bohle@uwyo.edu |
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Abstract: | 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. |
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Keywords: | Malaria pigment Vibrational spectroscopy Propionic acid dimer β-Hematin |
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