Judgment for DNA-binding modes of dye molecules by novel chain-aligned film method.

We have succeeded in preparation of novel composite films composed of chain-oriented DNA and the DNA-binding dyes aligned in specific orientation by drying the solution under a horizontal magnetic field. The dye-DNA composite films mostly showed linear dichroism, as revealed by polarized ultraviolet-visible spectroscopy (UV-VIS) and fluorescence anisotropy measurement. The intercalators such as ethidium bromide was fixed in chain-oriented DNA films in a similar binding manner as in solutions. Also, Hoechst 33258 was found to be aligned along the minor groove even in the solid films. In addition, by means of this film method, we could estimate the DNA-binding modes of newly designed original compounds. Here, we emphasize that the method using aligned dye-DNA films is very convenient for identifying the binding modes for double-stranded DNA.