Natural products as probes for nucleic acid structure and sequence.

Double helical DNA exists in a dynamic equilibrium among various forms, including partially unwound ones. The binding of molecules, including drugs and other natural products, influences this equilibrium. It produces changes in the physical properties of both the molecule and the DNA. Chemical changes such as covalent binding and DNA strand scission also occur. These changes can affect the replication and transcription of the DNA. The specific sites at which drugs bind to DNA can be determined by sequencing methods, including the Maxam-Gilbert and the "footprinting" technique of Galas and Schmitz.