XAFS studies of the synthetic substitutes of hemozoin
The local atomic structure around iron atoms of two synthetic analogues of malarial pigment product is characterized by iron K-edge X-ray absorption fine structure spectroscopy (XAFS). Malarial pigment, also termed hemozoin, is a condensed phase of ferriprotoporphyrin-IX dimers, and is structurally identical to the synthetic material hematin anhydride, which is also termed IS-hematin. Synthetic hemozoin analogues might serve as surrogates or models of malaria pigment for a range of fundamental laboratory methods, for example the design of new antimalarials. Two new iron(III)(protoporphyrin-IX) analogues, based on meso- and deuteroporphyrin are considered. Both new condensed phases are slightly soluble in many organic solvents. In the present work, the detailed examination of X-ray absorption spectra of monomer- and dimer-ferriprotoporphyrin-IX-based compounds is discussed. Parameters obtained by quantitative spectra analysis allow us to classify the new synthetic equivalents of the parasite product as dimer materials. X-ray absorption technique was able to distinguish dimer from monomer structures based on the structural disorder parameters of oxygen ligand bonding. (C) 2010 Elsevier B.V. All rights reserved.