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Transient electric birefringence of T7 viral DNA
Author(s) -
Rau Donald C.,
Bloomfield Victor A.
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.1979.360181110
Subject(s) - chemistry , dipole , electric field , birefringence , debye , relaxation (psychology) , molecular physics , flow birefringence , quadrupole , nuclear magnetic resonance , condensed matter physics , atomic physics , physics , optics , psychology , social psychology , organic chemistry , quantum mechanics
The electric birefringence properties of intact bacteriophage T7 DNA are investigated as a function of field strength and ionic environment. At low field strengths, E < 40 V/cm, Kerr behavior is observed. The birefringence decay kinetics are consistent with a Gaussian chain viscoelastic treatment for an induced dipole model of orientation. The observed relaxation time for the longest mode is 37 msec, in 0.5 m M Na + at 15°C, and is in agreement with flow experiments. In order to account for the observed differences in rise and decay kinetics, a field‐induced, anharmonic restoring force is postulated. The magnitude of the apparent induced dipole moment is found to be inversely proportional to the Debye‐Hückel shielding parameter κ for a series of Na + concentrations. The magnitude of the induced dipole moment is found to be very sensitive to the addition of Mg 2+ . When analyzed in terms of the counterion condensation theory of Manning, it appears that the induced dipole moment is proportional to the square of the reduced effective DNA charge density.