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Quasielastic light‐scattering studies on dinucleosomal‐sized DNA: Ionic‐strength dependence
Author(s) -
Schmitz Kenneth S.,
Lu Mei
Publication year - 1984
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360230417
Subject(s) - chemistry , ionic strength , ion , diffusion , rotational diffusion , dispersity , counterion , relaxation (psychology) , ionic bonding , light scattering , scattering , analytical chemistry (journal) , chemical physics , thermodynamics , aqueous solution , optics , chromatography , molecule , polymer chemistry , physics , organic chemistry , social psychology , psychology
Quasielastic light‐scattering (QELS) studies were performed on a monodisperse preparation of dinucleosomal‐sized DNA having an average of 375 base pairs. The QELS data were obtained at several time intervals at each angle examined over the range 30° < θ < 60° for the ionic strength solvents 500, 50, 10, and 1 m M in KCl. What results from this study is that two relaxation domains persist over the entire ionic strength range where the “splitting” between these two domains increases as the ionic strength is lowered. The ordinate intercept of D app vs C p /2 C s , where C p is the polyion concentration and C s is the added salt concentration, is shown to give the “true” hydrodynamic value for the diffusion coefficient. The “splitting phenomenon” is interpreted in terms of two models currently in vogue: small ion–polyion coupled modes and translational–rotational coupled modes for rigid rods in congested solutions. Although neither model is in perfect agreement with the experimental results, the small ion–polyion coupled mode theory appears to provide a better quantitative description of the observations.