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Biophys J, February 2000, p. 1018-1023, Vol. 78, No. 2
and
*Centro Brasileiro de Pesquisas Físicas, Rio
de Janeiro (RJ), 20290-180, and Universidade de
Brasília, Instituto de Física, Núcleo de
Física Aplicada, 70910-900, Brasília (DF), Brazil
Electron paramagnetic resonance was used to investigate
the magnetic material present in abdomens of Pachycondyla
marginata ants. A g 
4.3 resonance of
high-spin ferric ions and a very narrow g 2 line are
observed. Two principal resonance broad lines, one with
g > 4.5 (LF) and the other in the region of
g 2 (HF), were associated with the biomineralization
process. The resonance field shift between these two lines, HF and LF, associated with magnetic nanoparticles indicates the presence of
cluster structures containing on average three single units of
magnetite-based nanoparticles. Analysis of the temperature dependence
of the HF resonance linewidths supports the model picture of isolated
magnetite nanostructures of ~13 nm in diameter with a magnetic energy
of 544 K. These particles are shown to present a superparamagnetic
behavior at room temperature. The use of these superparamagnetic
particle properties for the magnetoreception process of the ants is suggested.
Biophys J, February 2000, p. 1018-1023, Vol. 78, No. 2
© 2000 by the Biophysical Society 0006-3495/00/02/1018/06 $2.00
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