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Dynamic light‐scattering studies of DNA. I. The coupling of internal modes with anisotropic translational diffusion in congested solutions
Author(s) -
Lee Wylie I.,
Schmitz Kenneth S.,
Lin SungChang,
Schurr J. Michael
Publication year - 1977
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.1977.360160309
Subject(s) - chemistry , autocorrelation , diffusion , anisotropy , relaxation (psychology) , macromolecule , coupling (piping) , mode coupling , rayleigh scattering , amplitude , rotational diffusion , normal mode , light scattering , molecular physics , scattering , physics , optics , quantum mechanics , materials science , social psychology , biochemistry , statistics , mathematics , metallurgy , vibration , psychology
A model for the coupling between internal modes, or molecular rotation, and anisotropic translational diffusion in congested solutions is proposed to account for the anomalously slow component that has appeared ubiquitously in reported autocorrelation functions of Rayleigh scattered light from solutions of DNA's with molecular weights greater than about 10 7 . The predicted existence of an anomalously slow mode in addition to a faster “normal” mode, as well as the predicted relative amplitudes of both fast and slow components, are qualitatively in agreement with the observations. For sufficiently long‐wavelength fluctuations all of the amplitude appears in the slower mode, which then exhibits an appropriately averaged translational diffusion coefficient. In support of the model it is shown in the Appendix that nonideal central interactions between macromolecules are by themselves insufficient to generate isolated internal mode relaxation terms in the autocorrelation function, unless translational ordering of the macromolecules extends over the illuminated observation region.