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. 2001 Jun 19;98(13):6986–6988. doi: 10.1073/pnas.141238898

Figure 1.

Figure 1

Two-step conversion of B-DNA to A-DNA by varying the two helix parameters slide and roll. (a) Initial idealized B-DNA. (b) Intermediate structure obtained by application of a uniform slide of −1.5 Å from one base pair to the next. (c) Alternative intermediate produced by applying a uniform roll of +12°. (d) A-DNA reached by varying both slide and role simultaneously. [Reproduced with permission from ref. 3 (Copyright 2000, National Academy of Sciences; original proposal by Calladine and Drew (12).]