Crystallization of synthetic haemozoin (β-haematin) nucleated at the surface of lipid particles

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dc.contributor.authorHoang A.N.
dc.contributor.authorNcokazi K.K.
dc.contributor.authorDe Villiers K.A.
dc.contributor.authorWright D.W.
dc.contributor.authorEgan T.J.
dc.date.accessioned2011-05-15T15:59:05Z
dc.date.available2011-05-15T15:59:05Z
dc.date.issued2010
dc.description.abstractThe mechanism of formation of haemozoin, a detoxification by-product of several blood-feeding organisms including malaria parasites, has been a subject of debate; however, recent studies suggest that neutral lipids may serve as a catalyst. In this study, a model system consisting of an emulsion of neutral lipid particles was employed to investigate the formation of β-haematin, the synthetic counterpart of haemozoin, at the lipid-water interface. A solution of monoglyceride, either monostearoylglycerol (MSG) or monopalmitoylglycerol (MPG), dissolved in acetone and methanol was introduced to an aqueous surface. Fluorescence, confocal and transmission electron microscopic (TEM) imaging and dynamic light scattering analysis of samples obtained from beneath the surface confirmed the presence of homogeneous lipid particles existing in two major populations: one in the low micrometre size range and the other in the hundred nanometre range. The introduction of haem (Fe(iii)PPIX) to this lipid particle system under biomimetic conditions (37 °C, pH 4.8) produced β-haematin with apparent first-order kinetics and an average half life of 0.5 min. TEM of monoglycerides (MSG or MPG) extruded through a 200 nm filter with haem produced β-haematin crystals aligned and parallel to the lipid-water interface. These TEM data, together with a model system replacing the lipid with an aqueous organic solvent interface using either methyl laurate or docosane demonstrated that the OH and CO groups are apparently necessary for efficient nucleation. This suggests that β-haematin crystallizes via epitaxial nucleation at the lipid-water interface through interaction of Fe(iii)PPIX with the polar head group. Once nucleated, the crystal grows parallel to the interface until growth is terminated by the curvature of the lipid particle. The hydrophobic nature of the mature crystal favours an interior transport resulting in crystals aligned parallel to the lipid-water interface and each other, strikingly similar to that seen in malaria parasites. © The Royal Society of Chemistry 2010.
dc.description.versionArticle
dc.identifier.citationDalton Transactions
dc.identifier.citation39
dc.identifier.citation5
dc.identifier.issn14779226
dc.identifier.other10.1039/b914359a
dc.identifier.urihttp://hdl.handle.net/10019.1/10996
dc.subjectAqueous surfaces
dc.subjectCo-group
dc.subjectDocosane
dc.subjectEpitaxial nucleation
dc.subjectFirst order kinetics
dc.subjectHaemozoin
dc.subjectHalf lives
dc.subjectHydrophobic nature
dc.subjectLaurate
dc.subjectLipid particles
dc.subjectMalaria parasite
dc.subjectMechanism of formation
dc.subjectModel system
dc.subjectMonoglycerides
dc.subjectNanometres
dc.subjectNeutral lipid
dc.subjectPolar headgroups
dc.subjectSize ranges
dc.subjectTEM
dc.subjectTransmission electron
dc.subjectWater interface
dc.subjectAcetone
dc.subjectBiomimetics
dc.subjectCrystals
dc.subjectDetoxification
dc.subjectDissolution
dc.subjectEmulsification
dc.subjectIron compounds
dc.subjectLight transmission
dc.subjectMethanol
dc.subjectNucleation
dc.subjectOrganic solvents
dc.subjectParticle size analysis
dc.subjectPhase interfaces
dc.subjectdipalmitoylphosphatidylcholine
dc.subjectheme
dc.subjecthemoprotein
dc.subjecthemozoin
dc.subjectlipid
dc.subjectarticle
dc.subjectchemistry
dc.subjectcrystallization
dc.subjectinfrared spectrophotometry
dc.subjectkinetics
dc.subjecttransmission electron microscopy
dc.subjectX ray diffraction
dc.subject1,2-Dipalmitoylphosphatidylcholine
dc.subjectCrystallization
dc.subjectHeme
dc.subjectHemeproteins
dc.subjectKinetics
dc.subjectLipids
dc.subjectMicroscopy, Electron, Transmission
dc.subjectSpectrophotometry, Infrared
dc.subjectX-Ray Diffraction
dc.titleCrystallization of synthetic haemozoin (β-haematin) nucleated at the surface of lipid particles
dc.typeArticle
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