Potato spindle tuber viroid: circular dichroism spectrum and physical chemical studies of its interaction with ethidium bromide.

The presence and extent of base-paired secondary structure in the protein-free potato spindle tuber viroid RNA has been investigated by spectroscopic techniques. Dye-binding studies with the intercalating dye, ethidium bromide, indicate the presence of base-paired regions in the molecule. Variation of the induced chirality in the dye with the dye to RNA phosphate ratio indicate the presence of two base-paired regions in the molecule.