Orientation of DNA double strands in a Langmuir-Blodgett film

A cationic amphiphile monolayer was spread on a subphase containing DNA double strands and intercalating dyes, and the polyion complex DNA/dye/cationic monolayer was transferred to a substrate by the vertical dipping method. It was confirmed by X-ray diffraction patterns and polarized absorption spectra that the dye-intercalated DNA strands were aligned along the dipping direction in the LB film. DNA strands are not aligned in the LB film without intercalating dye molecules. When the DNA-lipid monolayers were deposited by a horizontal lifting method instead of a vertical dipping method, DNA strands were randomly oriented in the film. The orientation of DNAs was decreased when the monolayer packing was decreased by using a low surface pressure or an expanded monolayer. Thus, the rigid, dye-intercalated DNA strands could be oriented during the vertical dipping process.