Dielectric relaxation of DNA solutions. IV. Effects of salts and dyes

✍ Scribed by Masanori Sakamoto; Reinosuke Hayakawa; Yasaku Wada

• Publisher: Wiley (John Wiley & Sons)
• Year: 1980
• Tongue: English
• Weight: 425 KB
• Volume: 19
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1980.360190508

✦ Synopsis

Synopsis

T h e effects of salts (NaCI, I K l , Me4NCI, AgNO:!, MgCI?, ('uC'l2. anti Mn('l2) ;ind dyes (acridine orange and methylene blue) on the low-t'requency dielectric relaxation (0.1 Hz-30 kHz) of dilute aqueous solutions of DNA were investigated with varying salt or dye concentrations. Both the dielectric relaxation time 71, and the rotational relaxation time r rst imat.rd from the reduced viscosity decrease in quite parallel ways wit.h increasing M I P ( M / P being the normality ratio of cation to phosphate residue), reflecting the contraction ol IINA molecule due to electrostatic shielding and cation binding. The agreement hetween T / J and r through the whole range of' M / P supports our previous conclusion that the low-frequency relaxation of DNA arises from rotation of the molecule. The dielectric increment Ac also decreases with increasing M / f ' on account of both the contraction of DNA and the decrease in el'tective degree of dissociation oL'DNA. Ac as a function of MIP is interpreted in terms o l a quasi-permanent dipole due to counterion fluctuation. These effects of'cations are the strongest lor divnlent cations and rather weak for Na+, Li+, and Me.,Nt. Effects of dye on r,, and Af are RIS(I well explained by the rotation of' DNA molecule with a quasi-permanent dipole due 1 0 i.iiunterion fluctuation on the basis of intercalation of dye at Z)/P < 0.2 ( D / P being the molarity ratio of' dye to phosphate residue) and external binding a t 0.2 < D / P < 1.0. c