Abstract
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 μ = 4585 (at −20 °C) to 3843 (+20 °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 μ = 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 kBT at room temperature. Thus, the spin dynamics of the neighboring Fe3+ ions are strongly correlated, lending support to the superparamagnetism.
Highlights
We report that hemozoin nanocrystals demonstrate superparamagnetic properties, with direct measurements of the synthetic hemozoin magnetization
We analyzed the previously published experimental data on the separation of hemozoin nanocrystals in the magnetic field gradient, concluding that these natural nanocrystals are super paramagnetic with μ= 6783, a value even larger than that obtained for the synthetic crystals
Ab initio analysis of the model systems with two Fe3+ ions in the high-spin configuration coupled by two atomic chains with conjugated π-bonds results in the ground state with the total spin S = 5, with the excitation energy into other spin states being much larger than kBT = 200 cm−1 at room temperature
Summary
We report that hemozoin nanocrystals demonstrate superparamagnetic properties, with direct measurements of the synthetic hemozoin magnetization. Similar results were obtained from the analysis of the diffusion separation of natural hemozoin nanocrystals in the magnetic field gradient, with μ = 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. A different view is that only some 30% of the heme is converted to hemozoin, while the main neutralization occurs via direct degradation of heme with accumulation of iron in the parasite[2]. Based on the famous early work of Pauling[20,21] that determined two possible spin configurations of electrons in the heme iron as diamagnetic or paramagnetic, depending on its oxygenated or deoxygenated form, the hemozoin magnetic properties were considered paramagnetic in the majority of the recent studies that discussed its magnetic properties
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