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Dielectirc relaxation of DNA in aqueous solutions
Author(s) -
Sakamoto Masanori,
Kanda Hirohsi,
Hayakawa Reinosuke,
Wada Yasaku
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.1976.360150506
Subject(s) - chemistry , dielectric , relaxation (psychology) , aqueous solution , dipole , counterion , intermolecular force , dna , analytical chemistry (journal) , nuclear magnetic resonance , dielectric spectroscopy , molecule , electrode , ion , electrochemistry , organic chemistry , materials science , physics , biochemistry , psychology , social psychology , optoelectronics
Using a four‐electrode cell and a new electronic system for direct detection of the frequency differences specturm of solution impedance, the complex dielectric constant of calf thymus DNA ( M r = 4 × 10 6 ) in aqueous NaCl at 10°C is measured at frequencies ranging from 0.2 Hz to 30 kHz. The DNA concentrations are C p = 0.01% and 0.05%, and the NaCl concentrations are varied from C s = 10 −4 M to 10 −3 M . A single relaxation regions is found in this frequency range, the relaxation frequency being 10 Hz at C p = 0.01% and C s = 10 −3 M . At C p = 0.05% it is evidenced that the DNA chains have appreciable intermolecular interactions. The dielectric relaxaton time τ d at C p = 0.01% agrees well with the rotational relaxation time estimated from the reduced visocisty on the assumption that the DNA is not representable as a rigid rod but a coiled chain. It is concluded that the dielectric relaxiatioinis ascribed to the rotation of the molecule. Observed values of dielectric increment and other experimental findings are reasonably explained by assuming that the dipole moment of DNA results from the slow counterion fluctuation which has a longer relaxation time than τ d .