Geometry of DNA–dye intercalation complexes from the study of linear dichroic spectra of stretched films

Abstract

SynopsisFilms of DNA-dye complexes were combined with films of pure DNA deposited on poly-(vinyl alcohol) support and stretched. Reproducible dichroic spectra were obtained after equilibration of the stretched films at 93% relative humidity. Dye diffusion into the supporting poly(viny1 alcohol) matrix was eliminated. The long axis of intercalated acriflavine is perpendicular to the DNA helix axis; proflavine deviates slightly and 9-aminoacridine significantly from such an intercalation geometry. The dichroism of two mutually perpendicularly polarized transitions of 9-aminoacridine enabled us to determine both the angles of tilt and twist of the plane of the dye relative to the DNA helix in the complex.

Metal ion-directed cooperative DNA binding of small molecules

“…(3). The adsorption around 500 nm is attributed to the transition dipole moment that is parallel to the long axis of the dimer, 1 2 -Cu [36,37]. The LD signals of 1 2 -Cu decreased and showed ca.…”

Linear dichroism spectroscopy of nucleic acids

“…Highly concentrated solutions of DNA have been partially oriented by smearing on infra-red or ultraviolet transparent slides, by stroking with a second slide (Gray & Rubenstein, 1968), and by deposition of humid films of DNA on top of a polymer sheet which is then stretched (Kelly & Kurucsev, 1976). In addition, Rupprecht (1963) developed an elegant method ('the wet-spinning method') by which well-aligned rather large samples of DNA for NMR and infrared spectroscopy are prepared by extruding a DNA solution through a spinneret into a spinning bath of 75 % ethanol; during precipitation the DNA fibres are continuously stretched and wound on to a rotating cylinder.…”

“…The growth of LD r as a function of time, upon application of a weak gradient to a random solution of microtubules, was found to be consistent with the kinetics computed for the radial S{XZ) function of a three-dimensional ensemble of rigid rods subjected to laminar flow. The orientation relaxation after shear has been Wada, 1971Jackson & Mason, 1971Kelly & Kurucsev, 1976;Hogan et al 1979; al.…”

Complex formation between 3;3´‐diethylthiacarbocyanine iodide and DNA and its investigation in aqueous solution

“…Measurements of fluorescence quantum yields of the dye were carried out on an "Amico-Bowman" spectrofluorimeter with an R136 photomultiplier by the comparison with the standard, DTCC in methanol (with fluorescence quantum yield of 5% [10,11]). In this work, calf thymus DNA (Aldrich) purified by dialysis was used [12]. Concentration of DNA was determined by the use of extinction coefficient ε = 6700 M −1 cm −1 , which corresponds to the absorption of a base pair [13].…”