DNA structural forms

In the years that have passed since the publication of Wolfram Saenger's classic book on nucleic acid structure (Saenger, 1984), a considerable amount of new data has been accumulated on the range of conformations which can be adopted by DNA. Many unusual species have joined the DNA zoo, including new varieties of two, three and four stranded helices. Much has been learnt about intrinsic DNA curvature, dynamics and conformational transitions and many types of damaged or deformed DNA have been investigated. In this article, we will try to summarise this progress, pointing out the scope of the various experimental techniques used to study DNA structure, and, where possible, trying to discern the rules which govern the behaviour of this subtle macromolecule. The article is divided into six major sections which begin with a general discussion of DNA structure and then present successively, B-DNA, DNA deformations, A-DNA, Z-DNA and DNARNA hybrids. An extensive set of references is included and should serve the reader who wishes to delve into greater detai.