Dielectric relaxation of DNA solutions. III. Effects of DNA concentration, protein contamination, and mixed solvents

✍ Scribed by Masanori Sakamoto; Reinosuke Hayakawa; Yasaku Wada

• Publisher: Wiley (John Wiley & Sons)
• Year: 1979
• Tongue: English
• Weight: 545 KB
• Volume: 18
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1979.360181109

✦ Synopsis

Abstract

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.