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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.


Related in: MedlinePlus

(A) Background subtracted Cartesian plot of Q vs γ of the inner rings of the XRD pattern; (B) normalized azimuthal intensity variations Ihkl(γ) for different rings, dashed lines indicate symmetry angles, blue dashed lines are along the direction of the bacteria alignment and therefore the fiber axis.
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fig03: (A) Background subtracted Cartesian plot of Q vs γ of the inner rings of the XRD pattern; (B) normalized azimuthal intensity variations Ihkl(γ) for different rings, dashed lines indicate symmetry angles, blue dashed lines are along the direction of the bacteria alignment and therefore the fiber axis.

Mentions: Upon projecting the 2D XRD pattern onto a Cartesian grid (azimuthal angle γ vs Q), the diffraction rings become straight lines and the AID along the rings can be recognized more easily (Figure3). The AID Ihkl(γ) of the diffraction ring for a certain set of planes {hkl} were obtained by radial integration of the 2D-pattern and a localized background subtraction (see SI). The AID Ihkl(γ) of four Debye rings are shown in Figure 3B. Ihkl(γ) represents the normalized directional distributions of the hkl lattice in the sample. The symmetry of the pattern can be observed in the intensity distribution of the different planes. All the AID display line (mirror) symmetry at the angles indicated by the dashed lines at γ = 2°, 92°, 182° and 272°. In the 2D-XRD pattern, these angles correspond to the plane parallel to the direction of bacterial alignment (92° and 272°, blue line in Figure 3) and to the plane perpendi­cular to it (2° to 182°).


Magnetite Crystal Orientation in Magnetosome Chains.

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

(A) Background subtracted Cartesian plot of Q vs γ of the inner rings of the XRD pattern; (B) normalized azimuthal intensity variations Ihkl(γ) for different rings, dashed lines indicate symmetry angles, blue dashed lines are along the direction of the bacteria alignment and therefore the fiber axis.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4384753&req=5

fig03: (A) Background subtracted Cartesian plot of Q vs γ of the inner rings of the XRD pattern; (B) normalized azimuthal intensity variations Ihkl(γ) for different rings, dashed lines indicate symmetry angles, blue dashed lines are along the direction of the bacteria alignment and therefore the fiber axis.
Mentions: Upon projecting the 2D XRD pattern onto a Cartesian grid (azimuthal angle γ vs Q), the diffraction rings become straight lines and the AID along the rings can be recognized more easily (Figure3). The AID Ihkl(γ) of the diffraction ring for a certain set of planes {hkl} were obtained by radial integration of the 2D-pattern and a localized background subtraction (see SI). The AID Ihkl(γ) of four Debye rings are shown in Figure 3B. Ihkl(γ) represents the normalized directional distributions of the hkl lattice in the sample. The symmetry of the pattern can be observed in the intensity distribution of the different planes. All the AID display line (mirror) symmetry at the angles indicated by the dashed lines at γ = 2°, 92°, 182° and 272°. In the 2D-XRD pattern, these angles correspond to the plane parallel to the direction of bacterial alignment (92° and 272°, blue line in Figure 3) and to the plane perpendi­cular to it (2° to 182°).

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