Magnetic orientation of purple membranes demonstrated by optical measurements and neutron scattering

Neugebauer, D.-Ch.; Blaurock, A.E.

doi:10.1016/0014-5793(77)80266-4

Cited by 92 publications

(50 citation statements)

References 25 publications

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“…This explains why proteins and synthetic polypeptides exhibit magnetic orientation with the -helices parallel to the magnetic ®eld. In the literature, most of the studies focus on the magnetic birefringence (Cotton±Mouton effect) of aromatic or aliphatic compounds (Lonsdale, 1939) or biological systems (Neugebauer et al, 1977;Torbet et al, 1981;Yamagishi, 1990). The diamagnetic anisotropy is characterized by observation of the formation of oriented ®brin, of small crystals or by the anisotropy of a scattering pattern.…”

Section: Introductionmentioning

confidence: 99%

Protein crystals orientation in a magnetic field

1998

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Nucleation and crystal growth of hen egg-white lysozyme, bovine pancreatic trypsin inhibitor and porcine pancreatic -amylase were carried out in the presence of a magnetic ®eld of 1.25 T produced by small permanent magnets. Crystals were oriented in the magnetic ®eld, except when heterogeneous nucleation occurred. The orientation of protein crystals in the presence of a magnetic ®eld can be attributed to the anisotropic diamagnetic susceptibility of proteins resulting from the large anisotropy of the -helices due to the axial alignment of the peptide bonds.

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Section: Introductionmentioning

confidence: 99%

Protein crystals orientation in a magnetic field

1998

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“…(b) Orientation in molecular films in an air-water interface [8]. (c) Orientation by magnetic [9] or electric fields [lO,ll]. We have chosen method (a) to obtain oriented preparations of purple membrane, since it has been been found from X-ray diffraction measurements [6,7] that the purple membrane fragments orient themselves when dried on a glass slide with their membrane planes parallel to the glass surface.…”

Section: Introductionmentioning

confidence: 99%

Immobilization of bacteriorhodopsin and orientation of its transition moment in purple membrane

Korenstein

Hess

1978

FEBS Letters

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“…In collagen, the planar peptide groups are oriented at about 450 to the fiber axis and, consequently, the axis of smallest numerical diamagnetism is perpendicular to the fiber axis. These features provide qualitative explanation for the observed magnetic orientations of several proteins and synthetic polypeptides: namely, that the a-helical structures of poly(lysine hydrobromide), poly(glutamic acid), poly('y-ethyl-L-glutamate), a-keratins, muscle fibers, and bacteriorhodopsin orient with the a helices parallel to the magnetic field (7,11,12,(18)(19)(20)(21); that silk fibroin also orients axially (11); and that collagens orient diametrically (11). A more quantitative description is readily established by using the notation of Lonsdale (22).…”

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confidence: 98%

Structural origins of diamagnetic anisotropy in proteins.

Worcester¹

1978

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

183

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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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Magnetic orientation of purple membranes demonstrated by optical measurements and neutron scattering

Cited by 92 publications

References 25 publications

Protein crystals orientation in a magnetic field

Protein crystals orientation in a magnetic field

Immobilization of bacteriorhodopsin and orientation of its transition moment in purple membrane

Structural origins of diamagnetic anisotropy in proteins.

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