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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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One dimensional diffractogram I(Q) of wildtype MSR-1 cells, obtained by azimuthal integration, compared with the reference pattern of magnetite.
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fig02: One dimensional diffractogram I(Q) of wildtype MSR-1 cells, obtained by azimuthal integration, compared with the reference pattern of magnetite.

Mentions: Aligned bacteria of different strains (the wildtype and a ΔmamJ mutant of Magnetospirillum gryphiswaldense MSR-1, Magnetospirillum magneticum AMB-1, and Desulfovibrio magneticus RS-1) and isolated magnetosomes of the MSR-1 strain were investigated with high-resolution X-ray diffraction. The diffraction pattern of MSR-1 is shown in Supplementary Figure 1. As expected, the positions of the diffraction rings, displayed as peaks in the diffractogram (azimuthally integrated I(Q), Q = 4π sin (θ)/λ, where 2θ corresponds to the scattering angle and λ is the wavelength of the beam), can be indexed to magnetite (Figure 2). Importantly, the Debye rings show systematic variations in their azimuthal intensity distribution (AID), indicating a non-random orientation of the crystals within the sample.


Magnetite Crystal Orientation in Magnetosome Chains.

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

One dimensional diffractogram I(Q) of wildtype MSR-1 cells, obtained by azimuthal integration, compared with the reference pattern of magnetite.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4384753&req=5

fig02: One dimensional diffractogram I(Q) of wildtype MSR-1 cells, obtained by azimuthal integration, compared with the reference pattern of magnetite.
Mentions: Aligned bacteria of different strains (the wildtype and a ΔmamJ mutant of Magnetospirillum gryphiswaldense MSR-1, Magnetospirillum magneticum AMB-1, and Desulfovibrio magneticus RS-1) and isolated magnetosomes of the MSR-1 strain were investigated with high-resolution X-ray diffraction. The diffraction pattern of MSR-1 is shown in Supplementary Figure 1. As expected, the positions of the diffraction rings, displayed as peaks in the diffractogram (azimuthally integrated I(Q), Q = 4π sin (θ)/λ, where 2θ corresponds to the scattering angle and λ is the wavelength of the beam), can be indexed to magnetite (Figure 2). Importantly, the Debye rings show systematic variations in their azimuthal intensity distribution (AID), indicating a non-random orientation of the crystals within the sample.

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