Unusual DNA Structures and the Probes Used for their Detection

A veritable explosion in our knowledge of unusual DNA structures has occurred in recent years. Our enhanced knowledge about specific DNA sequences via DNA sequencing and cloning has been a contributory factor. Furthermore, the establishment of diverse types of methods for the detection and analysis of unusual DNA structures has also been important. For example, in the early days of left-handed Z-DNA (1979–1982), the only techniques available were x-ray diffraction on short oligonucleotides, circular dichroism, phosphorus NMR, and laser Raman spectroscopy. Today, at least 15 different types of physical, enzymatic, immunological, chemical, and spectroscopic methods are available. Studies have been conducted on recombinant plasraids, short synthetic oligonucleotides, as well as purified restriction fragments.