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.
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