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Quasielastic light scattering by biopolymers. III. Effect of ionic strength on internal dynamics of DNA
Author(s) -
Schmitz Kenneth S.
Publication year - 1979
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.1979.360180220
Subject(s) - chemistry , ionic strength , diffusion , relaxation (psychology) , ionic bonding , rotational diffusion , scattering , thermodynamics , polymer , light scattering , crystallography , analytical chemistry (journal) , ion , aqueous solution , optics , physics , chromatography , molecule , organic chemistry , psychology , social psychology
Quasielastic light‐scattering data on DNA in 0.1, 0.5, and 1.0 M NaCl, neutral pH, have been obtained in the scattering angle range 15 ⩽ θ ⩽ 50. The relaxation curves have been analyzed as a single exponential with a reciprocal relaxation time of the form 2 D eff K 2 , where K is the fluctuation vector [proportional to sin(θ/2)] and D eff is the effective diffusion coefficient. The 1/τ vs sin 2 (θ/2) curves exhibit two regions that are proportional to sin 2 (θ/2), in accordance with the Lee‐Schurr and Lin‐Schurr theories for independent segment‐mean force and Rouse‐Zimm flexible polymers, respectively. In the region KR < 1, where R is a characteristic length, D eff is simply the translational diffusion coefficient, whereas D eff in the region KR > 1 represents the diffusion coefficient for a polymer segment. The data reported here indicate that the “transition” region between the two K 2 extremes is strongly dependent on the ionic strength of the solvent. This observation, along with the salt variation of the segmental diffusion coefficient, suggests the internal dynamics of DNA are dependent on the ionic strength of the solvent. The relation of the present study to those of Lin and Schurr and of Caloin et al. is discussed.