Orientation of Nucleic Acids in High Magnetic Fields

Maret, Georg; Schickfus, M. von; Mayer, Andreas; Dransfeld, Klaus

doi:10.1103/physrevlett.35.397

Cited by 98 publications

(62 citation statements)

References 24 publications

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“…Anisotropic magnetic susceptibility is a phenomenon commonly seen in crystals of highly anisotropic atomic structure. It also has been noted in constituents of biological tissues, including muscle fibers (17), retinal rods (18), nucleic acids (19), proteins (20)(21)(22)(23), and lipid bilayers (24)(25)(26)(27). Because the proteins and lipid bilayers associated with white matter fibers are highly ordered, anisotropic susceptibility may have contributed to our present findings.…”

Section: Discussionsupporting

confidence: 51%

Sensitivity of MRI resonance frequency to the orientation of brain tissue microstructure

Lee

Shmueli²,

Fukunaga³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

247

316

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Recent advances in high-field (≥7 T) MRI have made it possible to study the fine structure of the human brain at the level of fiber bundles and cortical layers. In particular, techniques aimed at detecting MRI resonance frequency shifts originating from local variation in magnetic susceptibility and other sources have greatly improved the visualization of these structures. A recent theoretical study [He X, Yablonskiy DA (2009) Proc Natl Acad Sci USA 106:13558–13563] suggests that MRI resonance frequency may report not only on tissue composition, but also on microscopic compartmentalization of susceptibility inclusions and their orientation relative to the magnetic field. The proposed sensitivity to tissue structure may greatly expand the information available with conventional MRI techniques. To investigate this possibility, we studied postmortem tissue samples from human corpus callosum with an experimental design that allowed separation of microstructural effects from confounding macrostructural effects. The results show that MRI resonance frequency does depend on microstructural orientation. Furthermore, the spatial distribution of the resonance frequency shift suggests an origin related to anisotropic susceptibility effects rather than microscopic compartmentalization. This anisotropy, which has been shown to depend on molecular ordering, may provide valuable information about tissue molecular structure.

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Section: Discussionsupporting

confidence: 51%

Sensitivity of MRI resonance frequency to the orientation of brain tissue microstructure

Lee

Shmueli²,

Fukunaga³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

247

316

View full text Add to dashboard Cite

show abstract

“…A fascinating specimen for the biophysical study of magnetic field interactions was provided by Blakemore's accidental discovery of magnetotactic bacteria. 44 Approximately 2% of the dry mass of these aquatic organisms is iron, which has been shown by Mossbauer spectroscopy to be predominantly in the form of magnetite: Fe304.45 The magnetite crystals are arranged as chains of approximately [20][21][22][23][24][25][26][27][28][29][30] single domain cyrstals, as shown in Fig. 3.…”

Section: Despite the Weak Interaction Of Individual Macromoleculesmentioning

confidence: 99%

Mechanisms for Biological Effects of Magnetic Fields

Tenforde

1985

Biological Effects and Dosimetry of Static and ELF Electromagnetic Fields

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“…Oriented chlorophyll molecules were proposed as the components responsible for the diamagnetic anisotropy of chloroplasts and bacterial chromatophores since the planar, partially conjugated chlorophyll ring has very large diamagnetic anisotropy (6,13). In nucleic acids, the diamagnetic anisotropy was attributed to aromatic rings of base pairs, many of which are parallel in a DNA molecule because of the persistence length (8)(9). The magnetic orientation of retinal rod outer segments was attributed to diamagnetic anisotropy of the oriented rhodopsin molecules in the disc membranes (14), but no specific molecular groups of this protein were identified to be responsible.…”

mentioning

confidence: 99%

“…The orientation of retinal rod outer segments (1), chloroplasts (2-4), photosynthetic algae and bacteria (5,6), purple membranes (7), and nucleic acids (8,9) in magnetic fields of several kilogauss have been attributed to diamagnetic anisotropy of the molecular components. Earlier studies reported magnetic anisotropy in cellulosic materials (10,11), in silks, keratins, and collagens (11), and in muscle fibers (12).…”

mentioning

confidence: 99%

Structural origins of diamagnetic anisotropy in proteins.

Worcester¹

1978

Proc. Natl. Acad. Sci. U.S.A.

183

132

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Magnetic anisotropy in proteins and polypeptides can be attributed to the diamagnetic anisotropy of the planar petide bonds. The a helix in particular has large anisotropydue to the axial alignment of the peptide bonds. The regular arrangements of the peptide bonds in P pleated sheet and collagen structures also produce substantial anisotro y, but less than for a helix. The anisotropy permits orientation of small structures of these types in magnetic fields of several kilogauss.Magnetic anisotropy in biological materials has been increasingly reported. The orientation of retinal rod outer segments (1), chloroplasts (2-4), photosynthetic algae and bacteria (5,6), purple membranes (7), and nucleic acids (8,9) in magnetic fields of several kilogauss have been attributed to diamagnetic anisotropy of the molecular components. Earlier studies reported magnetic anisotropy in cellulosic materials (10,11), in silks, keratins, and collagens (11), and in muscle fibers (12). The molecular origins of the diamagnetic anisotropy have been identified for only a few of these phenomena. Oriented chlorophyll molecules were proposed as the components responsible for the diamagnetic anisotropy of chloroplasts and bacterial chromatophores since the planar, partially conjugated chlorophyll ring has very large diamagnetic anisotropy (6,13). In nucleic acids, the diamagnetic anisotropy was attributed to aromatic rings of base pairs, many of which are parallel in a DNA molecule because of the persistence length (8-9). The magnetic orientation of retinal rod outer segments was attributed to diamagnetic anisotropy of the oriented rhodopsin molecules in the disc membranes (14), but no specific molecular groups of this protein were identified to be responsible. More recently, it was proposed that oriented aromatic rings of the peptide side chains in rhodopsin could account for the magnetic anisotropy (15). Oriented lipid molecules in the disc membranes were considered not to be responsible because of the relatively weak diamagnetic anisotropy of long chain fatty acids (16) and because the orientations of these hydrocarbon chains in the lipid bilayers of the membranes would result in orientation of the opposite sense to that observed (14). Similarly, the magnetic orientation of purple membranes of Halobacterium halobium was attributed to the oriented molecules of bacteriorhodopsin (7), although in this case linear dichroism measurements in the region of 280 nm showed that aromatic groups cannot be responsible because their net orientation is in the wrong direction (17).The findings of magnetic anisotropy in silks, keratins, collagens, muscle fibers, retinal rods, and purple membranes suggest that diamagnetic anisotropy is frequently present in protein structures. Oriented aromatic groups of the peptide side chains could be responsible for some of these anisotropies. However, in addition to the results for purple membranes, reports of magnetic orientation of poly(L-glutamic acid) (18), poly(L-lysine hydrobromide) (19) The publication ...

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Orientation of Nucleic Acids in High Magnetic Fields

Cited by 98 publications

References 24 publications

Sensitivity of MRI resonance frequency to the orientation of brain tissue microstructure

Sensitivity of MRI resonance frequency to the orientation of brain tissue microstructure

Mechanisms for Biological Effects of Magnetic Fields

Structural origins of diamagnetic anisotropy in proteins.

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