Critical single domain grain sizes in chains of interacting greigite particles: Implications for magnetosome crystals.
Авторы: Muxworthy A., Williams W., Roberts A.
GGG (Geochem., ...)
Magnetotactic bacteria contain chains of magnetically interacting crystals (magnetosomes), which aid
navigation (magnetotaxis). To improve the efficiency of magnetotaxis, magnetosome crystals (which can
consist of magnetite or greigite) should be magnetically stable single domain (SD) particles. Larger
particles subdivide into nonuniform multidomain (MD) magnetic structures that produce weaker
magnetic signals, while small SD particles become magnetically unstable due to thermal fluctuations and
exhibit superparamagnetic (SP) behavior. In this study, we determined the stable SD range as a function
of grain elongation and interparticle separation for chains of identical greigite grains using fundamental
parameters recently determined for greigite. Interactions significantly increase the stable SD range. For
example, for cube-shaped greigite grains the upper stable SD threshold size is increased from 107 nm for
isolated grains to 204 nm for touching grains arranged in chains. The larger critical SD grain size for
greigite means that, compared to magnetite magnetosomes, greigite magnetosomes can produce larger
magnetic signals without the need for intergrain interactions.