Chemistry Reference
In-Depth Information
a
c
d
e
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B-DNA
Z-DNA
DNA BRs
f
g
h
b
Fig. 20 DNA nanotechnology ushers in beautiful DNA topologies. (a) Synthesis of DNA
Borromean Rings [
135
] from complimentary three-stranded junctions. (b) Double-helix [2]
catenane [
136
]. (c-h) Images of DNA M
obius strips (c AFM, d TEM, e graphical), and their
corresponding [2]catenanes (f AFM, g TEM, h graphical) [
137
]. Reproduced with permission from
[
44
] (copyright 2005 American Chemical Society), [
136
] (copyright 2011 American Chemical
Society), [
137
] (copyright 2010 Nature Publishing Group)
€
In mathematics, links can be characterized by an extension of knot theory using
Alexander-Briggs notation, where each link is represented by the number of
crossings in its two-dimensional projection, with a superscript denoting the number
of interlocked rings and a subscript denoting its (arbitrary) order among links with
the same crossing number [
142
]. Fig.
21
shows the 18 prime links (composite links
are a combination of one or more prime links) with less than eight crossings,
demonstrating that chemical topology is still a largely unexplored and exciting
challenge; only 2
1
;
and 6
2
have been reproduced as synthetic molecules to date.
Other novel topologies (effectively composite links) and architectures have also
been prepared, and will be addressed in Sect.
4.2
.
4
1
;
Fig. 21 Projections of the 18
prime links with less than
eight crossings
