Superparamagnetic properties of hemozoin

We report that hemozoin nanocrystals demonstrate superparamagnetic properties, with direct measurements of the synthetic hemozoin magnetization. The results show that the magnetic permeability constant varies from mu = 4585 (at -20 degrees C) to 3843 (+20 degrees C), with the values corresponding to a superparamagnetic system. Similar results were obtained from the analysis of the diffusion separation of natural hemozoin nanocrystals in the magnetic field gradient, with mu = 6783 exceeding the value obtained in direct measurements by the factor of 1.8. This difference is interpreted in terms of structural differences between the synthetic and natural hemozoin. The ab initio analysis of the hemozoin elementary cell showed that the Fe3+ ion is in the high-spin state (S = 5/2), while the exchange interaction between Fe3+ electron-spin states was much stronger than k(B)T at room temperature. Thus, the spin dynamics of the neighboring Fe3+ ions are strongly correlated, lending support to the superparamagnetism

Immunoprecipitation of [(3)H]Dihydroartemisinin Translationally Controlled Tumor Protein (TCTP) Adducts from Plasmodium falciparum-Infected Erythrocytes by Using Anti-TCTP Antibodies

Artemisinin and its derivatives are endoperoxide-containing antimalarial drugs that appear to form adducts in situ with the Plasmodium falciparum translationally controlled tumor protein (TCTP) homolog. Immunoprecipitation with antibody to recombinant TCTP suggests that adducts may form with both monomeric and dimeric TCTP

Novel endoperoxide antimalarials: Synthesis, heme binding, and antimalarial activity

Copyright © 2004 American Chemical SocietyWe report the synthesis of a series of novel epoxy endoperoxide compounds that can be prepared in high yields in one to three steps from simple starting materials. Some of these compounds inhibit the growth of Plasmodium falciparum in vitro. Structure-activity studies indicate that an endoperoxide ring bisubstituted with saturated cyclic moieties is the pharmacophore. To study the molecular basis of the action of these novel antimalarial compounds, we examined their ability to interact with oxidized and reduced forms of heme. Some of the compounds interact with oxidized heme in a fashion similar to chloroquine and other 4-aminoquinolines, while some of the compounds interact with reduced heme. However, the level of antimalarial potency is not well correlated with these activities, suggesting that some of the endoperoxides may exert their antimalarial activities by a novel mechanism of action.Dennis K. Taylor, Thomas D. Avery, Ben W. Greatrex, Edward R. T. Tiekink, Ian G. Macreadie, Peter I. Macreadie, Adam D. Humphries, Martha Kalkanidis, Emma N. Fox, Nectarios Klonis and Leann Tille