Topography of Nucleic Acid Helices in Solutions. Proton Magnetic Resonance Studies of the Interaction Specificities of Steroidal Amines with Nucleic Acid Systems

The interactions of steroidal amines with nucleic acid helices are reported. The studies were based on Tm of helix-coil transitions of nucleic acid-steroid complexes, as well as viscometric, circular dichroism, and temperature-dependent proton magnetic resonance techniques. The results indicate that the steroidal amines selectively stabilize the DNA helical structures, while causing the ribose-containing acids to unravel and denature. The temperature-dependent proton magnetic resonance experiments show that single stranded random coils interact with the steroidal amines via hydrogen- and hydrophobic-type bonding. The capacity to form hydrogen bonding in the random coils is shown to be greater than that of the helical structure.