Forward depolarized dynamic light scattering from wormlike chains

Abstract

The forward depolarized light scattering correlation function is calculated for a dilute solution of polymers modeled as elastic wormlike chains in the free-draining limit. The polymer is represented hydrodynamically by an effective cylindrically symmetric body and characterized by a single end-over-end rotational diffusion coefficient, 8. The correlation function for N polymer molecules is an infinite series of decaying exponentials of the form C(t) = (Np2/15)e~tClkajkbjk(U) exp[-l)(xp + Xk4)t/(2d2)], where p is the segment optical anisotropy, D is the translational diffusion coefficient, L is the contour length, and a = XL is the number of Kuhn lengths. The quantities xi N (2j + 1)7r/2 are eigenvalues of the elastic bending problem.An important feature of the above result is the combination of rotational and flexural contributions to the time constants of the relaxation terms. The relative contribution of each of these processes is a function of flexibility. Comparison with Brownian dynamics simulations indicates that the weights are greatly affected by the neglect of hydrodynamic interactions in the theory. Nevertheless, this equation is the first calculation of the depolarized scattering from a semiflexible molecule that has the correct rigid rod limit. It should also be applicable for the description of the field-free decay of the birefringence from molecules without a permanent dipole moment. The theory is in good agreement with experimental data from DNA restriction fragments.

Diffusion and segmental dynamics of rodlike molecules by fluorescence correlation spectroscopy

“…[49][50][51] The detailed analysis exhibits a strong influence of the rotational motion on the time dependence of the FCS correlation function for a certain range of polymer lengths. Since actin filaments or fd viruses are within that length scale, FCS provides the opportunity to measure their rotational diffusion coefficient.…”

“…͑8͔͒ leads to much simpler normal mode amplitude correlation functions than those obtained by Aragón. [49][50][51] In particular, the various modes form an orthogonal set. The reason is the more adequate treatment of the first mode, which is artificially introduced in the weakly bending rod model.…”

“…3 As will be shown, this leads to simpler and more adequate mode amplitude correlation functions than those following from the original approach. [49][50][51] The article is organized as follows. In the next section the model is described and its equation of motion is solved.…”

A dynamic light scattering study of a 2311 base pair DNA restriction fragment

“…Thus the decay curves contain information only about the internal motions (or perhaps overall rotation). 34,35 In DLS the translational diffusion of the entire coil contributes a pure diffusion peak (see eq 2 and 3) and also contributes a term to all of the other relaxation modes. Because the pure translational diffusion peak is close in decay time to the decay times of the internal motions, it affects the measurement of their decay times and amplitudes.…”

Depolarized light scattering from prolate anisotropic particles: The influence of the particle shape on the field autocorrelation function

“…The early starting point for the lasting interest in the diffusive motion of anisotropic particles is the well-known work of Perrin. 5 Experimental access to rotational diffusion is possible via dynamic light scattering employing laser light [6][7][8][9][10][11][12][13] or coherent X-rays 14 as a probe. With near-field depolarized dynamic light scattering, in a heterodyne experiment, very small scattering vectors can be accessed.…”