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Dielectric relaxation of DNA solutions. III. Effects of DNA concentration, protein contamination, and mixed solvents
Author(s) -
Sakamoto Masanori,
Hayakawa Reinosuke,
Wada Yasaku
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.1979.360181109
Subject(s) - chemistry , dielectric , relaxation (psychology) , dipole , viscosity , solvent , counterion , analytical chemistry (journal) , dna , thermodynamics , nuclear magnetic resonance , chromatography , organic chemistry , ion , materials science , biochemistry , social psychology , physics , optoelectronics , psychology
As a continuation of previous papers [ Biopolymers (1976) 15 , 879; (1978) 17 , 1508], the low‐frequency dielectric relaxation of DNA solutions was studied with a four‐electrode cell and the simultaneous two‐frequency measurement. Below a critical concentration, the dielectric relaxation time agrees with the rotational relaxation time estimated from the reduced viscosity and is almost independent of DNA concentration C p , and the dielectric increment is proportional to C p . The critical concentration is approximately 0.02% of DNA for molecular weight M r 2 × 10 6 and 0.2% for M r 4.5 × 10 5 in 1 m M NaCl. Dielectric relaxations are compared for samples before and after deproteinization, and the protein contamination is found to have a minor effect on the dipole moment of DNA. The effect of a mixed solvent of water and ethanol on the dielectric relaxation of DNA is well interpreted in terms of changes in viscosity and the dielectric constant of the solvent, assuming that the relaxation arises from rotation of the molecule with a quasi‐permanent dipole due to counterion fluctuation.