Electric Properties of Macromolecules. IV. Determination of Electric and Optical Parameters from Saturation of Electric Birefringence in Solutions

O’Konski, Chester T.; Yoshioka, Koshiro; Orttung, William H.

doi:10.1021/j150580a004

Cited by 451 publications

(224 citation statements)

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“…The magnitude of p depends on the angle a between the chromophore transition moment and the molecular orientation, expressed by the orientation function 4) defined by O'Konski et al (10) (0 < 4 < 1). Specifically (11), p=2 (3cos ca-1)4 [2] in which 4) is a complicated function of the field, whose form depends on the angular dependence of the potential energy (10).…”

mentioning

confidence: 99%

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Transient electric dichroism of rod-like DNA molecules.

Hogan¹,

Dattagupta²,

Crothers³

1978

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

193

124

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We report transient electric dichroism studies on monodisperse rod-like DNA molecules. By using restriction fragments and DNAs of known length, it is shown that the orientation time is accurately predicted by the theoretically calculated rotational diffusion coefficient. The field dependence of the steady-state dichroism values is not consistent with the induced electric dipole orientation mechanism, and the time dependence is not consistent with the presence of a permanent dipole moment. In order to explain the dependence of the dichroism on the electric field, the ionic strength of the medium, and the length of the macromolecule, we propose a new model in which anisotropic ion flow produces an asymmetric ion atmosphere around the polyelectrolyte, resulting in an orienting torque. From the limiting dichroism at high field, we estimate that the DNA bases are inclined at an angle of 730 or less relative to the helix axis, in good agreement with the revised model of B-form DNA suggested by Levitt, in which the base pairs have a propeller-like twist. Our results establish transient electric dichroism measurements as a technique well suited for study of alterations in the length and base pair inclination of rod-like DNA molecules.Electric dichroism, a form of linear dichroism induced in a solution of optically anisotropic macromolecules that have permanent or induced electrical anisotropy, is potentially of great value for study of structural alterations in DNA (1-5). Theory indicates that the orientation time should depend on the third power of the length of rod-like double helical fragments, whereas the dichroism amplitude, extrapolated to perfect molecular orientation, depends on the angle between the electronic transition moment and the molecular orientation axis. These features make electric dichroism well suited to such problems as change in DNA length and base pair orientation when drug or protein molecules are bound. However, for several reasons, this potential has not been fully realized. Monodisperse DNA fragments are required, and the restriction enzymes necessary for their production have only recently become widely available. Furthermore, electric dichroism equipment capable of resolving orientation times of a few microseconds and operating at salt conditions of at least 1 mM to avoid irreversible degradation (6) is not generally available. Perhaps most important, the physical origin and general properties of the orienting force have not been clear, because the field-dependence of the dichroism implies a constant or permanent dipole moment (3), whereas the 2-fold symmetry of the DNA phosphodiester chains in a double helix rules out a permanent molecular dipole moment directed along the helix axis.The purpose of this paper is to show that electric dichroism can be used to obtain accurate values for the length of DNA molecules in the size range 100-250 base pairs, to characterize the variables that control the dichroism, and to suggest a new model for the origin of the torque in the electric fiel...

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confidence: 99%

“…These are the two standard mechanisms for electric field-induced orientation of macromolecules, for which the orientation function 4l has been calculated by O'Konski et al (10). The potential energy U depends on the electric field E, according to the equations U = -,E cos 6 (permanent moment)…”

mentioning

confidence: 99%

Transient electric dichroism of rod-like DNA molecules.

Hogan¹,

Dattagupta²,

Crothers³

1978

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

193

124

View full text Add to dashboard Cite

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“…If such a particle has a thickness d then 12R:, = d2 sional form (Y and p are given by the one-dimenof the equations in [ 151. The plot of RF against l/p has an intercept and 1 z @ 3 -0.5). The variation of @ as a function of AxH2/2kT is different for positive or negative Ax [24,25]. We have used the magnetically induced birefringence An to monitor orientation, An = An,@ where An, = birefringence when Cp = 1.…”

Section: Neutron Scatteringmentioning

confidence: 99%

“…As Ans and @ can be positive or negative the sign of Ax cannot be directly deduced from that of An. By fitting the measured An curve, if it covers a sufticient range, with the theoretical plot for @, Ax can be determined in sign and magnitude [24,25]. The plots of ZcQZ@ against p gave a straight line within a range 0.6 < QRt < 1.…”

Section: Neutron Scatteringmentioning

confidence: 99%

“…As the magnetic orientation of diamagnetically anisotropic particles is the analogue of induced electric dipole orientation the theory of the latter in [24,25] can be easily adapted for the former. Consider a dilute suspension of non-interacting rigid particles which have an axis of rotational symmetry in their diamagnetic and optical properties.…”

Section: Magnetically Induced Birefringencementioning

confidence: 99%

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The structure of the cell wall of Staphylococcus aureus studied with neutron scattering and magnetic birefringence

Torbet¹,

Norton²

1982

FEBS Letters

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The cell wall complex was extracted from Staphylococcus aureus and characterized in suspension by means of small-angle neutron scattering and magnetically induced birefringence. The neutron scattering measurements show that the complex has a thickness of -420 A, a mass per unit area of 93 + 11 daltons/A2and is -75% water by volume. The neutron scattering density is higher near the surface than in the interior in accordance with a trilamellar structure. The magnetically induced birefringence measurements demonstrate that a high degree of magnetic orientation is possible due to the anisotropic nature of the wall complex structure. Staphylococcus aureus Peptidoglycan Cell wall Magnetic orientationNeutron scattering, small angle

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Polarization of counterions in polyelectrolytes

Mohanty

Zhao

1998

Biopolymers

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A theory of the polarization of counterions bound to a polyion, such as a DNA, in low and high electric field strengths is developed using statistical mechanics of inhomogeneous systems. For low fields, one finds that the polarizability p is (Zq)2 ρ0βL3/(12[1 + Lρ0σ(L, b, ζ, Z, I, ρ0)]J), where σ = ∫10 (λ′ − λ0 {dc(λ − λ′)/dλ}λ = λ0 dλ′J), Z and L are the valence and the length of the polyion, respectively, q is the proton charge, β = 1/kBT, T is the temperature, kB is the Boltzmann constant, I is the ionic strength, λ = x/L and λ0 = x0/L are scaled distances, x0 is a reference point such that the inhomogeneous counterion density at x0 is equal to ρ0—the uniform density in the absence of an electric field E—and c(x) is the direct correlation function of the homogeneous counterion‐polyion phase, which includes attractive and repulsive interactions. If Lσ(L, .) is much less than one, then the polarizability is proportional to L3. If the term Lσ(L, .) is much larger than one, the polarizability scales as L2. The induced dipole moment saturates and its value is the same as that of Mandel‐Manning theories. The onset of the saturation, however, depends critically on the direct correlation function and hence polyelectrolyte effects. In the formalism, the polarization of the counterions is the equilibrium response to an electric field provided E is less than Esaturated. A dynamical scheme that incorporates the fact that in high fields the bound counterions conduct is discussed. © 1996 John Wiley & Sons, Inc.

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Electric Properties of Macromolecules. IV. Determination of Electric and Optical Parameters from Saturation of Electric Birefringence in Solutions

Cited by 451 publications

References 0 publications

Transient electric dichroism of rod-like DNA molecules.

Transient electric dichroism of rod-like DNA molecules.

The structure of the cell wall of Staphylococcus aureus studied with neutron scattering and magnetic birefringence

Polarization of counterions in polyelectrolytes

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