Nanocrystallography measurements of early stage synthetic malaria pigment.

Ruben A Dilanian,Nicholas W Phillips,Keith A Nugent,Victor Streltsov,Andrew V Martin,Brian Abbey,Con Dogovski,Harry M Quiney,Sophie Williams,Nectarios Klonis,Sébastien Boutet,Hannah D Coughlan,Garth J Williams,Marc Messerschmidt,Leann Tilley

doi:10.1107/s1600576717012663

Abstract

The recent availability of extremely intense, femtosecond X-ray free-electron laser (XFEL) sources has spurred the development of serial femtosecond nanocrystallography (SFX). Here, SFX is used to analyze nanoscale crystals of β-hematin, the synthetic form of hemozoin which is a waste by-product of the malaria parasite. This analysis reveals significant differences in β-hematin data collected during SFX and synchrotron crystallography experiments. To interpret these differences two possibilities are considered: structural differences between the nanocrystal and larger crystalline forms of β-hematin, and radiation damage. Simulation studies show that structural inhomogeneity appears at present to provide a better fit to the experimental data. If confirmed, these observations will have implications for designing compounds that inhibit hemozoin formation and suggest that, for some systems at least, additional information may be gained by comparing structures obtained from nanocrystals and macroscopic crystals of the same molecule.

Highlights

Plasmodium falciparum is the causative agent of the most severe form of malaria in humans
X-ray diffraction data were collected at the macromolecular crystallography beamlines, MX1 and MX2, at the Australian Synchrotron and at the Linac Coherent Light Source (LCLS) X-ray free-electron laser (XFEL)
The greater similarity between the MX1 and MX2 data compared to the XFEL data arises because, even after filtering, the sample consists of crystals that range in size from $50 nm up the largest size allowed through by the filter, $1 mm

Summary

Introduction

Plasmodium falciparum is the causative agent of the most severe form of malaria in humans. During the blood stage of its lifecycle the malaria parasite invades red blood cells It develops through the early (ring) stage to the mature (trophozoite) stage and divides in the schizont stage. FP is a toxic molecule that can damage membranes and proteins (Balla et al, 2007; Becker et al, 2004; Kumar & Bandyopadhyay, 2005) To avoid these toxic effects the parasite sequesters FP into non-reactive crystals, known as hemozoin or malaria pigment. Efforts to design improved quinolines require a detailed understanding of the process of formation of hemozoin, and the structural properties of the initiating crystals

Results

Discussion

Conclusion