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Magnetite Crystal Orientation in Magnetosome Chains.

Körnig A, Winklhofer M, Baumgartner J, Gonzalez TP, Fratzl P, Faivre D - Adv Funct Mater (2014)

Bottom Line: One-dimensional magnetic nanostructures have magnetic properties superior to non-organized materials due to strong uniaxial shape anisotropy.The obtained pole figure patterns reveal a [111] fiber texture along the chain direction for magnetospirilla strains MSR-1 and AMB-1, whereas a [100] fiber texture is measured for Desulfovibrio magneticus strain RS-1.The pronounced fiber textures can be explained either by a strain-specific biological control on crystal orientation at the chain level or by physical alignment effects due to intra-chain magnetic interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces Science Park Golm, 14424, Potsdam, Germany.

ABSTRACT

One-dimensional magnetic nanostructures have magnetic properties superior to non-organized materials due to strong uniaxial shape anisotropy. Magnetosome chains in magnetotactic bacteria represent a biological paradigm of such magnet, where magnetite crystals synthesized in organelles called magnetosomes are arranged into linear chains. Two-dimensional synchrotron X-ray diffraction (XRD) is applied to cells of magnetotactic bacteria that are pre-aligned with a magnetic field to determine the crystallographic orientation of magnetosomes relative to the chain axis. The obtained pole figure patterns reveal a [111] fiber texture along the chain direction for magnetospirilla strains MSR-1 and AMB-1, whereas a [100] fiber texture is measured for Desulfovibrio magneticus strain RS-1. The [100] axis appears energetically unfavorable because it represents a magnetic hard axis in magnetite, but can be turned into an effective easy axis by particle elongation along [100] for aspect ratios higher than 1.25, consistent with aspect ratios in RS-1 magnetosomes determined earlier. The pronounced fiber textures can be explained either by a strain-specific biological control on crystal orientation at the chain level or by physical alignment effects due to intra-chain magnetic interactions. In this case, biological control of the axis of elongation would be sufficient to influence the crystallographic texture of the magnetosome chain.

No MeSH data available.


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AID of different Debye rings of cells of AMB-1, a ΔmamJ mutant of MSR-1, RS-1 cells and isolated magnetosomes from MSR-1. The direction of the magnetic field applied during the drying process is indicated by dashed lines. In the RS-1 graphs, the black lines indicate expected intensity maxima for a [100] fiber texture (see SI for their calculations).
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fig04: AID of different Debye rings of cells of AMB-1, a ΔmamJ mutant of MSR-1, RS-1 cells and isolated magnetosomes from MSR-1. The direction of the magnetic field applied during the drying process is indicated by dashed lines. In the RS-1 graphs, the black lines indicate expected intensity maxima for a [100] fiber texture (see SI for their calculations).

Mentions: Not surprisingly, a [111] fibre texture with similar HWHM was also observed for cells of the AMB-1 strain (Figure4). This strain, too, forms cubooctahedral magnetosome crystals, albeit with slightly larger elongation than MSR-1 does, and assembles the magnetosome in a similar, although more fragmented chain arrangement. The magnetosome crystals of this strain also assemble with their [111] direction along the chain axis and thus along the bacterial pole to pole direction.


Magnetite Crystal Orientation in Magnetosome Chains.

Körnig A, Winklhofer M, Baumgartner J, Gonzalez TP, Fratzl P, Faivre D - Adv Funct Mater (2014)

AID of different Debye rings of cells of AMB-1, a ΔmamJ mutant of MSR-1, RS-1 cells and isolated magnetosomes from MSR-1. The direction of the magnetic field applied during the drying process is indicated by dashed lines. In the RS-1 graphs, the black lines indicate expected intensity maxima for a [100] fiber texture (see SI for their calculations).
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4384753&req=5

fig04: AID of different Debye rings of cells of AMB-1, a ΔmamJ mutant of MSR-1, RS-1 cells and isolated magnetosomes from MSR-1. The direction of the magnetic field applied during the drying process is indicated by dashed lines. In the RS-1 graphs, the black lines indicate expected intensity maxima for a [100] fiber texture (see SI for their calculations).
Mentions: Not surprisingly, a [111] fibre texture with similar HWHM was also observed for cells of the AMB-1 strain (Figure4). This strain, too, forms cubooctahedral magnetosome crystals, albeit with slightly larger elongation than MSR-1 does, and assembles the magnetosome in a similar, although more fragmented chain arrangement. The magnetosome crystals of this strain also assemble with their [111] direction along the chain axis and thus along the bacterial pole to pole direction.

Bottom Line: One-dimensional magnetic nanostructures have magnetic properties superior to non-organized materials due to strong uniaxial shape anisotropy.The obtained pole figure patterns reveal a [111] fiber texture along the chain direction for magnetospirilla strains MSR-1 and AMB-1, whereas a [100] fiber texture is measured for Desulfovibrio magneticus strain RS-1.The pronounced fiber textures can be explained either by a strain-specific biological control on crystal orientation at the chain level or by physical alignment effects due to intra-chain magnetic interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomaterials, Max Planck Institute of Colloids and Interfaces Science Park Golm, 14424, Potsdam, Germany.

ABSTRACT

One-dimensional magnetic nanostructures have magnetic properties superior to non-organized materials due to strong uniaxial shape anisotropy. Magnetosome chains in magnetotactic bacteria represent a biological paradigm of such magnet, where magnetite crystals synthesized in organelles called magnetosomes are arranged into linear chains. Two-dimensional synchrotron X-ray diffraction (XRD) is applied to cells of magnetotactic bacteria that are pre-aligned with a magnetic field to determine the crystallographic orientation of magnetosomes relative to the chain axis. The obtained pole figure patterns reveal a [111] fiber texture along the chain direction for magnetospirilla strains MSR-1 and AMB-1, whereas a [100] fiber texture is measured for Desulfovibrio magneticus strain RS-1. The [100] axis appears energetically unfavorable because it represents a magnetic hard axis in magnetite, but can be turned into an effective easy axis by particle elongation along [100] for aspect ratios higher than 1.25, consistent with aspect ratios in RS-1 magnetosomes determined earlier. The pronounced fiber textures can be explained either by a strain-specific biological control on crystal orientation at the chain level or by physical alignment effects due to intra-chain magnetic interactions. In this case, biological control of the axis of elongation would be sufficient to influence the crystallographic texture of the magnetosome chain.

No MeSH data available.


Related in: MedlinePlus