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  • Author: M. Wilkinson x
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Abstract

The magnetic structure of NiWO4 has been determined from neutron-diffraction measurements on single-crystal specimens. It is a collinear anti-ferromagnet in which the nickel ions have moments of 2.25 ± 0.04 μ B at 19.4 ± 2.6° to the c axis in obtuse β. The form factor of the Ni++ ions follows closely the free-ion form factor. CoWO4 is shown to have an isomorphous magnetic structure.

Abstract

Reactive oxygen species are the unwanted by-products of aerobic metabolism. To protect cells against their potentially lethal effects a series of pathways have evolved that are collectively called the oxidative defence system. In most eukaryotes, catalases and selenium-dependent glutathione peroxidases form the front line of defence against hydroperoxide-mediated damage. However, these activities are lacking in members of the Trypanosomatidae family of protozoan parasites. Instead these organisms contain several enzyme-mediated pathways for removal of hydroperoxides that are centred upon the unusual thiol trypanothione. Here we discuss the biochemical properties of one group of these enzymes, the non-selenium glutathione-dependent peroxidases, and outline the roles that they play in protecting the parasite against hydroperoxides associated with biological membranes.