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The optical birefringence of DNA solutions induced by oscillatory electric and hydrodynamic fields
Author(s) -
Wilkinson Robert S.,
Thurston George B.
Publication year - 1976
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.1976.360150810
Subject(s) - birefringence , flow birefringence , polarizability , dipole , chemistry , relaxation (psychology) , electric field , dielectric , kerr effect , dispersion (optics) , molecular physics , condensed matter physics , physics , optics , quantum mechanics , molecule , psychology , social psychology , organic chemistry , nonlinear system
The optical birefringence induced in DNA solutions by both oscillating hydrodynamic fields (flow birefringence) and oscillating electric fields (Kerr effect) is measured over a wide frequency range. The observed frequency response of the birefrigence is compared with theories for rigid ellipsoidal particles and for Gaussian chains. DNA at 6 × 10 5 molecular weight is found to exhibit rigid particle hydrodynamic behavior, while DNA at 5 × 10 6 molecular weight behaves like a flexible chain. Characterization of the hydrodynamic relaxation spectra for the DNA's by oscillatory flow birefringence allows precise comparison between theory and the experimental Kerr effect response. The dielectric model for DNA contains both permanent and dispersionless induced dipole moments. The dielectric behavior of DNA has the character of a permanent dipole but with anomalous low‐frequency dispersion in the Kerr effect. The existing theories do not adequately describe this dispersion. A fluctuation dipole mechanism with relaxation times comparable to those associated with the hydrodynamic motion could possibly demonstrate the observed polar behavior.