title: Displacement of sodium ions by surfactant ions from DNA. A 23Na-NMR investigation.
abstract: 23Na-NMR probes the ionic composition in the immediate vicinity of the DNA molecule, in the presence of a series of quaternary ammonium bromides, of varying hydrocarbon chain length. The 23Na-NMR line shows two Lorentzian components, in accordance with quadrupolar relaxation theory for S = 3/2 nuclei under slow modulation. Deconvolution of the observed lineshape provides, in a reliable manner, the relative fraction of sodium counterions neutralizing the phosphate sites on DNA. This quantity (p B chi 2) serves as an index of the relative affinities of various surfactant ions toward DNA, Na+ being the reference cation. The results are consistent with site binding of detergent ions to the nucleic acid, an interaction dominated by hydrophobic forces.
mesh_terms: D000818:Animals; D002412:Cations; D002417:Cattle; D004247:DNA; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D000644:Quaternary Ammonium Compounds; D012964:Sodium; D013329:Structure-Activity Relationship; D013501:Surface-Active Agents; D013950:Thymus Gland
chemical_list: D002412:Cations; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; D004247:DNA; D012964:Sodium