ACTINOMYCIN D AS A PROBE FOR NUCLEIC ACID SECONDARY STRUCTURE.

The binding of actinomycin D to DNA results in an increase in the temperature at which thermal dissociation of the DNA occurs. With this enhancement of thermal stability as a criterion for binding, it is shown that complementary RNA and DNA-RNA hybrid do not bind actinomycin D. This result can be interpreted to mean that these polynucleotides have helical conformations which differ from that of DNA.