Figure 5.
Fig. 5. Calladine-Drew base-centered mechanism for the
B-to-A helix transition. (a) B DNA with neither slide nor roll.
(b) B DNA with addition of a 1.5-Å
slide. (c) B DNA with addition of a +12° roll. (d) A DNA,
resulting from addition of both slide and roll to B DNA. The
G[3]C[3] helix corresponds to the helix in b and can be regarded
as a B DNA helix to which slide has been added but not roll.
Conversely, it can be thought of as A DNA from which roll has
been removed. Figures were created with NUSTAR (X.-J. Lu and W.
K. Olson, unpublished work).
1.5-Å
slide. (c) B DNA with addition of a +12° roll. (d) A DNA,
resulting from addition of both slide and roll to B DNA. The
G[3]C[3] helix corresponds to the helix in b and can be regarded
as a B DNA helix to which slide has been added but not roll.
Conversely, it can be thought of as A DNA from which roll has
been removed. Figures were created with NUSTAR (X.-J. Lu and W.
K. Olson, unpublished work).