Anomalous electric birefringence behavior of sonicated DNA fragments as observed in reversing-pulse transients and steady-state sign reversal: a multicomponent approach

Anomalous electric birefringence signals of a sonicated and column-fractionated medium-size calf thymus DNA sample (bp  =  570) in Na⁺ solutions were measured at 7 °C. The reversing-pulse electric birefringence (RPEB) signal pattern was theoretically calculated in the low electric field region for two axially symmetric models coexisting in equilibrium in solution. The RPEB theory is based on the electric dipole moment due to ion-fluctuation along the longitudinal direction and the electric polarizability anisotropy (Δ′), together with various electric and optical parameters assigned to the models. An analytical method was developed for the steady-state birefringence of the two-component system in a wide range of electric fields. The NaDNA samples exhibit complex RPEB patterns mixed with negative- and positive-going profiles. An experimental RPEB signal of NaDNA at an absorbance (A₂₆₀) of 8 was fitted to theoretical curve at weak electric fields. The anomalous RPEB signal was attributed to the component 2, which shows a dip in the buildup and another in the reverse processes with a positive sign and a larger relaxation time. For the component 1, a normal DNA profile with negative sign is associated with a narrow dip in the reverse and a faster relaxation time in the decay signal. The field-strength dependence of observed steady-state birefringence δ(∞) could be fitted for NaDNA at A₂₆₀  =  8 by the SUSID orientation function with saturated ionic and electronic moments. An apparent positive maximum and the sign reversal in δ(∞) at weak electric fields is an interplay between the positive component 2 with positive optical factor Δg and negative Δ′ and the negative component 1 with negative Δg and positive Δ′. Possible conformation of two DNA components involved in solution was estimated.     

The collision-induced polarizability of a pair of hydrogen molecules

Collision-induced light scattering, impulsive stimulated scattering, and subpicosecond-induced birefringence all depend on the transient changes Deltaalpha in molecular polarizabilities that occur when molecules collide. Ab initio results for Deltaalpha are needed to permit comparisons with accurate experimental results for these spectra and for refractive index virial coefficients and dielectric virial coefficients. In this work, we provide results for Deltaalpha for a pair of hydrogen molecules, treated at CCSD(T) level, with an aug-cc-pV5Z (spdf) basis set. Our values replace the best previous ab initio results for the variation of Deltaalpha with intermolecular separation, the self-consistent-field results obtained by Bounds [Mol. Phys. 38, 2099 (1979)] with a relatively small (3s2p) basis set for H2. For the six geometrical configurations studied by Bounds, the inclusion of correlation and improvements in the basis tend to increase both the trace Deltaalpha(0)0 and the anisotropy Deltaalpha2m of the pair polarizability. The change in the anisotropy is relatively small, but our values for the trace differ by factors of 2 or more from Bounds' results. For use in computing experimental line shapes, intensities, and virial coefficients, we have calculated Deltaalpha for 18 different relative orientations of a pair of H2 molecules, with the intermolecular separation R ranging from 2 a.u. (3 a.u. for a linear pair) to 10 a.u. The H2 bond length is fixed at the vibrationally averaged internuclear separation in the ground state r=1.449 a.u. Our results agree well with the CCSD(T) results for Deltaalpha obtained by Maroulis [J. Phys. Chem. A 104, 4772 (2000)] for two pair configurations of H2...H2 (linear and T-shaped) at a fixed internuclear distance of R=6.5 a.u. in a [6s4p1d] basis. As the intermolecular distance increases (for R>or=8 a.u.), the spherical-tensor components of Deltaalpha converge to the results from a long-range model that includes dipole-induced-dipole (DID) interactions, higher-multipole induction, nonuniformity of the local field, hyperpolarization, and van der Waals dispersion. Deviations from the first-order DID model are still evident for R between 8 and 10 a.u. in most orientations of the pair. At shorter range, overlap damping, exchange, and orbital distortion reduce both Deltaalpha0(0) and Deltaalpha(2)0 below their long-range limiting forms.     

Hyperpolarizability of GaAs dimer is not negative

We present a systematic study of the static electric hyperpolarizability of Ga(2)As(2). The authors rely on finite-field high-level ab initio calculations with carefully optimized basis sets. Their best values for the mean and the anisotropy of the dipole polarizability are alpha=158.57 and Deltaalpha=130.33e(2)a(0) (2)E(h) (-1). For the hyperpolarizability we propose an estimate gamma=(155+/-15)x10(3)e(4)a(0) (4)E(h) (-3), which does not agree with the negative value predicted by Lan et al. [J. Chem. Phys. 124, 094302 (2006)]. Density functional theory based methods yield values close to those predicted by conventional ab initio methods. The (hyper)polarizability components are particularly enhanced along the direction defined by the Ga-Ga axis.     

A theory for the rise of the electric birefringence of rigid macromolecules at high field strength

Summary A theory for the rise of the electric birefringence of rigid macromolecules, which holds for arbitrary field strength in the initial stage, is proposed. This theory is compared with the previous theories for low field strength and for infinitely high field strength. Based on this theory it is possible to determine the permanent dipole moment and the anisotropy of electrical polarizability separately from measurements of electric birefringence at high fields.

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Zusammenfassung Eine Theorie für den Einschaltvorgang der elektrischen Doppelbrechung starrer Makromoleküle für beliebige Feldst?rken im Anfangsverlauf wird vorgeschlagen. Diese Theorie wird mit den früheren Theorien für kleine Feldst?rken und für unendlich hohe Feldst?rken verglichen. Auf Grund dieser Theorie ist es m?glich, durch Messungen der elektrischen Doppelbrechung im starken Feld das permanente Dipolmoment und die Anisotropie der elektrischen Polarisierbarkeit getrennt zu bestimmen.

     

Bonding and (hyper)polarizability in the sodium dimer

We report a conventional ab initio and density functional theory study of the polarizability (alpha(alphabeta)/e(2)a(0) (2)E(h) (-1)) and hyperpolarizability (gamma(alphabetagammadelta)/e(4)a(0) (4)E(h) (-3)) of the sodium dimer. A large [18s14p9d2f1g] basis set is thought to yield near-Hartree-Fock values for both properties: alpha=272.28, Deltaalpha=127.22 and gamma=2157.6 x 10(3) at R(e)=3.078 87 A. Electron correlation has a remarkable effect on the Cartesian components of gamma(alphabetagammadelta). Our best value for the mean is gamma=1460.1 x 10(3). The (hyper)polarizability shows very strong bond-length dependence. The effect is drastically different for the longitudinal and transverse components of the hyperpolarizability. The following first derivatives were extracted from high-level coupled cluster calculations: (dalpha/dR)(e)=54.1, (dDeltaalpha/dR)(e)=88.1e(2)a(0)E(h) (-1), and (dgamma/dR)(e)=210 x 10(3)e(4)a(0) (3)E(h) (-3). We associate the (hyper)polarizability to bonding effects between the two sodium atoms by introducing the differential property per atom Q(diff)/2 identical with (Q[Na(2)(X (1)Sigma(g) (+))]/2-Q[Na((2)S)]). The differential (hyper)polarizability per atom is predicted to be strongly negative for the dimer at R(e), as [alpha(Na(2))/2-alpha(Na)]=-33.8 and [gamma(Na(2))/2-gamma(Na)]=-226.3 x 10(3). The properties calculated with the widely used B3LYP and B3PW91 density functional methods differ significantly. The B3PW91 results are in reasonable agreement with the conventional ab initio values. Last, we observe that low-level ab initio and density functional theory methods underestimate the dipole polarizability anisotropy. Experimental data on this important property are highly desirable.     

Electric polarizability of DNA in aqueous salt solution

Monte Carlo simulations are performed to determine the anisotropy of the electric polarizability of a model DNA fragment in aqueous salt solution. By taking into consideration the participation of coions in the electroneutrality condition, at every simulation step, we obtain a list of counterions constituting the net charge arranged in increasing order of their distance from the DNA and calculate the contribution to the dipole moment from the first n counterions in the list. We define a partial polarizability tensor due to these n counterions to understand the origin of the polarizability in close relation to the solution structure. The ionic distributions are described by the counterion condensation theory. Characteristic features of the electric properties of polyelectrolytes are reproduced. The anisotropy of the electric polarizability Deltaalpha of DNA decreases with the addition of salt, yielding values comparable to experiment. The effect of electrophoretic motion of the polyion is examined by estimating its upper limit.     

Auto-Organisation in Silica-Based Organic-Inorganic Gels Obtained by Sol-Gel Process

A new type of hybrid material is prepared through sol-gel processing by the polycondensation of (MeO)₃Si–R–Si(OMe)₃ units containing a rigid organic anisotropic group R. The hybrid covalently bounded organic-inorganic gel shows an unexpected structural birefringence n (n = 2 × 10^–3). This birefringence is induced by a strain field anisotropy during gel aging as revealed by simultaneous dynamic light scattering and birefringence measurements. To better address the role of the strain field, we use a free interface sol-gel/air to control strain anisotropy and to measure the gel optical axis and its birefringence. We find that the birefringence is associated to a long-range orientational order of organic moieties induced by the strain anisotropy during the gel aging.     

High-resolution laser spectroscopy on the S1<--S0 transition of jet-cooled anthracene: rotational structure and Stark effect

We present rotationally resolved spectra of the S(1)<--S(0) transition of anthracene at 27,687.153(4) cm(-1) as well as Stark effect measurements of the free anthracene molecule in electric fields of up to 85 kV/cm. The molecule is rotationally cooled in a supersonic jet expansion to a temperature of 4 K. The rotational constants of the electronic states S(0) and S(1) are determined by a simplex fit comparing the experimental spectra with simulations for an asymmetric rigid rotor. The measured and simulated energies are in very good agreement and the estimated accuracy of the rotational constants is 1 per thousand. Furthermore, the polarizabilities of the electronic states S(0) and S(1) are investigated. At an electric field of 85 kV/cm, line shifts of up to 150 MHz caused by a change in the polarizability of Deltaalpha=123(7) a.u. and broadenings due to the anisotropy are observed. The components of the tensor polarizabilities of the electronic states S(0) and S(1) are determined by simulating the complete spectra using second-order perturbation theory.     

Theoretical birefringence of ultraoriented polyethylene from model structure calculations

The birefringence of model structures of ultraoriented polyethylene has been calculated by using the point-dipole concept and the polarizability tensor of the methylene group derived recently by Pietralla. For well-oriented chains the birefringence is determined by the combination of a negative anisotropy of the polarizability tensor of the methylene group and a positive anisotropy of the Lorentz tensor, both with respect to the chain direction. As a consequence it decreases with increasing density. The results are in agreement with experimental values of Mead, Desper, and Porter. In the model the amorphous regions are regarded as a mixture of planar and helical segments arranged in nematiclike bundles which additionally may have a certain distribution of orientation. The birefringence is not much affected by defects which, on the other hand, strongly influence the ultimate mechanical properties.     

The electric birefringence of polyelectrolytes: an electrokinetic approach

We discuss the Kerr constant of a polyelectrolyte solution in the dilute regime. We show that the birefringence induced in a suspension of nonspherical polyelectrolytes by an external electric field probes the electrokinetic properties of the suspension. This is because the Kerr constant is directly connected to the electric torque exerted on the particles, and therefore contains information on the induced dipole, similarly to the other electrokinetic techniques. The article is a guideline for the development of an electrokinetic theory of the electric birefringence of polyelectrolytes. We compare two different methods to derive the Kerr constant of the polyelectrolyte solution. The first method uses an expression for the electric torque which is obtained through electrostatics, and yields a Kerr constant which has the same frequency dependence as the anisotropy of the real part of the polarizability of the dressed particle (that is, of the particle plus surrounding ions). The second method assigns an effective value of the induced electric dipole per particle by using the theory of the dielectric enhancement, and gives a Kerr constant proportional to the anisotropy of the real part of the dielectric constant of the suspension. The two methods give a considerably different frequency dependence of the Kerr constant: we suggest that the expression obtained by the second method is more capable of correctly describing the main features of the experimental results obtained with polyelectrolytes having small shape anisotropy.     

Flow birefringence of temporary polymer networks

The statistical theory of temporary polymer networks is an effort of describing the macroscopic behavior of such networks based on molecular behavior analysis. The calculation of the stress tensor of a network and the satisfactory comparison with experimental viscosity results was shown before [Rheol. Acta 28 (1989) 193]. Here we present the foresights of the theory as regards flow birefringence. The polarizability tensor is calculated first and then the birefringence of a four-functional temporary polymer network is estimated for a stationary simple shear flow. The dependence of the calculated quantities on shear rate is in line with existing experimental evidence.     

Electric birefringence anomaly of solutions of ionically charged anisometric particles

The term “electric birefringence anomaly” is known as the electric birefringence (EB) signal that occurs in solutions of ionically charged anisometric particles in a narrow concentration region. The signal is of opposite sign to the normal birefringence that occurs below and above this narrow concentration region. The normal electric birefringence signals in the dilute and more concentrated regions are due to the orientation of the particles in the direction of the applied electric field. The origin for the anomalous signal was not completely understood until now.     

Relaxational behavior of birefringence of aqueous carboxymethylcellulose under an alternating electric field at frequencies ranging from 0.1 Hz to 100 kHz

The d. c. component of birefringence of aqueous carboxymethylcellulose (CMC) under an a. c. electric field was measured at frequencies ranging from 0.1 Hz to 100 kHz. Three samples of different molecular weights were studied with varying degree of neutralization, polymer concentration and added salt concentration. The dispersion curve of birefringence consists of three relaxation bands,A, B andC in order of decreasing frequency. RelaxationB with a negative relaxation strength is ascribed to end-over-end rotation of almost rodlike CMC molecules. RelaxationA with a positive strength is attributed to the relaxation of electrical polarizability along the minor axis of molecule. RelaxationC possesses also a positive strength and is induced by clusters of CMC molecules.Dedicated to Prof. Dr. F. H. Müller.     

Reversing-pulse electric birefringence of multicomponent systems: the formulation and signal simulation for two axially symmetric components in equilibrium and the appearance of unusual signal patterns

This paper consists of two parts on reversing-pulse electric birefringence (RPEB) signal patterns. The first is the theoretical formulation of two axially symmetric models coexisting in equilibrium in solution. The present RPEB theory is based on the original Tinoco-Yamaoka theory with classical electric dipole moments, which was recently modified and extended by Yamaoka, Sasai, and Kohno to include various electric and optical parameters and most importantly the ion-fluctuation dipole moment (1/2) along the longitudinal direction of axially symmetric molecules. The theory contains the electric polarizability anisotropy Deltaalpha', which can be either positive or negative in relation to the shape of components. The overall signal can be expressed as the sum of the fractions of two components in proportions to the coefficient F(1) or F(2) (=1-F(1)). The second part is the simulation of theoretical RPEB curves for the two-component system with various sets of electric and hydrodynamic parameters for hypothetical but interesting cases. In consideration of the decay behavior, calculated decay curves were compared with experimentally conceivable signals, classifying them into three categories according to cases: F(1)>1, 0/ktDeltaalpha(') is the crucial factor that controls the pattern of RPEB signals. If q value of one component is positive and the other is negative, the simulated RPEB curves are characterized by three cases: q>0, q<-1, and -10 or q<-1, the resultant patterns are often encountered with experimental signals. If -1相似文献   

Dielectric Relaxation Around a Charged Colloidal Cylinder in an Electrolyte

The polarizability and corresponding dielectric relaxation of the Debye-Hückel (DH) atmosphere surrounding a charged rod-like polyelectrolyte immersed in an ionic solution of a symmetrical electrolyte is determined following the method developed by J. A. Fornés [Phys. Rev. E 57, 2110 (1998)]. Several formulas are given to estimate the DH atmosphere parameters, namely, the polarizability at zero frequency, alpha(0), the relaxation time, tau, the cloud capacitance, C, the average displacement of the ionic cloud, delta, the square root dipole moment quadratic fluctuation, (1/2), and the thermal fluctuating field, (1/2). The Poisson-Boltzmann equation is solved numerically to apply the theory to a highly charged polyelectrolyte such as DNA in solution, although formulas valid for the DH approximation are also given. A dispersion in the polarizability and correspondingly in the dielectric constant of these solutions in the microwave region is predicted. For instance, considering a DNA length of 1000 ?, with its reduced linear charge density xi(0)=4.25 and ionization factor gamma=0.5, immersed in a NaCl solution (40 mM), we predict a polarizability of the DH atmosphere at zero frequency alpha(0) of 1x10(-33) Fm(2) ( approximately 6.1x10(6)) times greater than the mean value of the polarizability of water) and the corresponding fluctuating dipole moment p of 2.1x10(-27) Cm ( approximately 600 times greater than the permanent dipole moment of water molecule). The relaxation time and the average displacement of the ionic cloud are tau=1.6 ns and delta=14. ?, respectively. This displacement is produced by the thermal fluctuating field, which, in this case, at room temperature is (1/2)=2 x10(6) V/m. Copyright 2000 Academic Press.     

Magneto-optics of Ferritin

Measurements of Rayleigh light scattering, nonlinear light scattering in DC magnetic fields, and the Cotton-Mouton effect were carried out for 15 mM NaCl and water solutions of ferritin at room temperature. The spherical geometry of the molecule implies that it is optically isotropic. Such a macromolecule should not manifest magnetic anisotropy; however, in solution it shows induced magnetic birefringence (Cotton-Mouton effect) and changes in the intensity of the scattered light components. The analysis of the obtained results indicates the deformation of linear optical polarizability induced in the ferritin by a magnetic field as the main source of the magneto-optical phenomena observed. Light scattering and the CM effects theoretically depend on the linear magneto-optical polarizability, chi, and the nonlinear magneto-optical polarizability, eta. Using the theory describing the phenomena as well as the experimental data, the values of the anisotropy of linear magneto-optical polarizability components, chi(parallel) - chi(perpendicular) = -(1.3 +/- 0.7) x 10(-22) [cm3] (in SI units chi(parallel) - chi(perpendicular) = -(2.0 +/- 1.2) x 10(-33) [m3]), the linear optical polarizability, alpha = (alpha(parallel) + 2alpha(perpendicular))/3 = (3.9 +/- 1.0) x 10(-20) [cm3] (in SI units alpha = (3.52 +/- 0.09)x10(-4) [Cm2 V(-1)]), and its anisotropy, kappa(alpha) = (alpha(parallel) - alpha(perpendicular))/3alpha = -(0.06+/-0.03), nonlinear magneto-optical polarizability, eta = (eta(parallel) + 2eta(perpendicular))/3 = -(4.7 +/- 0.9) x 10(-30) [cm3 Oe(-2)] (in SI units eta = -(6.7 +/- 1.3) x 10(-18) [Cm4 V(-1) A(-2)]) and its anisotropy, kappa(eta) = (eta[parallel) - eta(perpendicular))/3eta = -(0.15 +/- 0.10), were deduced. Here alpha(parallel), eta(parallel), alpha(perpendicular), eta(perpendicular) are the optical and magneto-optical polarizability components along the parallel and the perpendicular axes of the axially symmetric molecule, respectively.     

Electrooptics of beta-FeOOH particle in aqueous media 2. Field-strength dependence of decay and steady-state birefringence, and the hydrodynamic and electrooptic properties

Steady-state and decay birefringence, expressed in terms of the optical phase retardation per cell length delta/d, was measured on beta-FeOOH in aqueous ionic media at 633 nm and at 25 degrees C by an electric square-pulse technique over a wide range of field strength E to ca. 6 kV/cm. The field-strength dependence of both delta/d and field-free rotational relaxation time tau was determined at the sample concentrations between 0.0011 and 0.055 g/L and in the 0.02-2.0 mM NaCl concentration range. Extrapolation of both delta/d and tau values to infinitely high fields (E(2)-->infinity) could yield birefringence- and weight-average quantities, respectively. Observed tau values were decreased at weak fields but leveled off to ca. 0.3 ms at very high fields due to a slight polydispersity regarding the length and volume of particles. The weight-average relaxation time tau(w) was calculated with Perrin's expressions theoretically from the length, width, and volume of beta-FeOOH particles estimated in the dried state from electron micrograph. These quantities were variously averaged. The size distribution was discussed in terms of observed discrete histogram and theoretical (Weibull and Lansing-Kraemer) distribution functions. The sign of observed delta/d value was always positive. The infinitely high-field (delta/d)(infinity) values and the reduced optical anisotropy factor Delta g/n were evaluated by fitting to theoretical orientation functions. The intrinsic birefringence (n3-n1) could be estimated with the mean refractive index n(p) reported in the literature. For the spindle-shaped particle with an axial ratio of ca. 4, the sign of Delta g/n is always positive, whereas the quantity (n3-n1) was either negative (n(p) > 2.35) or positive (n(p) < 2.05) in sign or nearly zero (ca. n(p) = 2.26), depending critically on the n(p) values.     

Deformation,scattering, and birefringence of flexible polymer chains under external forces or electric fields

The effect of a tensile stress or an electric field on the conformation of a flexible polymer chain has been studied by combining theory with numerical simulation. In the presence of such external agents, the macromolecule experiences the action of two opposite forces at the chain ends. Two models are considered: the Gaussian bead-and-spring chain, and the freely jointed chain with segments of fixed length. From simulated Brownian trajectories we calculate steady-state properties of the polymer under the continuing action of the external forces. Thus, we compute the chain deformation and expansion, measured by the square radius of gyration, and analyze the influence of the external force on low-angle scattering of radiation. The effect of the link orientation in the optical anisotropy or birefringence is also analyzed. From existing theories, we predict very simple relationships between expansion, low-angle scattering, and birefringence, valid for Gaussian chains of any length, and for long freely jointed chains. The simulation results confirm those relationships. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys, 35: 689–697, 1997     

On orientational and distortional contributions to birefringence

A model for the effect of orientation dependence of polarizability anisotropy on birefringence is given and compared with literature data. If this dependence arises through bond angle distortion, the model shows a significant contribution to birefringence but a very small contribution to strain, accounting satisfactorily for differences in birefringence between hot-drawn and cold-drawn samples, for discrepancies between measurements of orientation obtained by different experimental methods and for previous observations on orientational behavior of preorientated polycarbonate at low additional strain.     

Electro-optical studies on synthetic polyelectrolytes—II: Electric birefringence of poly-N-butyl-4-vinylpyridinium salts in aqueous solution

The field strength dependence of the electric birefringence of poly- N-butyl-4-vinylpyridinium bromide in aqueous solution changes markedly with polymer concentration. Analysis of the orientation curves reveals that the mean electric polarizability ?Δα sharply increases when the concentration decreases, as a result of the extension of the chain, while the negative optical anisotropy factor remains unchanged. An empirical relationship, similar to that found for the reduced viscosity, is derived for the variation of electric polarizability with concentration.Increasing the ionic strength produces a coiling of the polyelectrolytic chain and a decrease of ?Δx. The replacement of the bromide ions by sulphate ions causes a conformational change evidenced by a decrease of ?Δα and of the relaxation time. This effect is interpreted by the formation of electrostatic bonding between the pyridinium rings on non-adjacent segments of the chain, and to a limited extend, by intermolecular bonding.The dependence of the relaxation time, extrapolated to infinite dilution, on the molecular weight of the samples is analysed on the basis of a worm-like chain model. The persistent length obtained is found of the same order of magnitude as in the case of other semi-rigid polymers. The predominant influence of the segmental orientation on the optical, electric or conformational parameters is discussed in detail.