Rich, Alex

The most striking conformational variant observed for a DNA double helix with Watson-Crick base pairing is referred to as the Z form. In Z DNA the backbone is twisted in the left-handed (counterclockwise) direction. This structure was first detected by Alex Rich and his co-workers (fig. 25.8). The Z form is a considerably slimmer helix than the B form and contains 12 bp/turn rather than 10. In the Z form, the planes of the base pairs are rotated approximately 180° with respect to the helix axis from their orientation in the B form (fig. 25.9). 

Provided with a rich set of mapping scenarios, one can test different aspects of a mapping tool. The effectiveness of the tool is the percentage of these scenarios that the tool could successfully implement. This approach is the one followed by STBenchmark [Alexe et al. 2008b], The scenarios the benchmark provides have been collected from the related scientific literature and real-world applications. 

We would like to acknowledge our collaborators in Alex Rich s laboratory at M.I.T., especially F. L. Suddath, Gary Quigley, and Alex McPherson, for the X-ray diffraction data used in this work and for helpful discussions. 

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