Biomedical Engineering Reference
In-Depth Information
Fig. 11.5
(
a
) Construction and operation of the molecular tweezers (Reprinted by permission from
Macmillan Publishers Ltd: Ref. [
42
], copyright 2000). (
b
) Scheme of a DNA nanomotor. The
DNA motor consists of two single strands:
E
and
F
.The
E
strand contains a 10-23 DNAzyme
domain. The
F
strand has a rhodamine
green
fluorophore at the 5
0
end and a
black hole
quencher-
1 (BHQ-1) at the 3
0
end (Reprinted with permission from Ref. [
43
]. Copyright 2004 American
Chemical Society). (
c
) Closing of DNA tweezers controlled by mRNA produced by transcription
and subsequent opening of tweezers by a removal strand (Reprinted with permission from Ref.
[
45
]. Copyright 2004 American Chemical Society)
10-23 DNAzymes. In the absence of the substrate, the single-stranded DNAzyme
collapsed into a closed coil with divalent cations, which brought the two arms
close to each other. In the presence of its DNA-RNA chimera substrate, the single-
stranded DNA enzyme formed a bulged duplex with the substrate, pushing the
two arms apart and leading to an open state of the tweezers. Upon binding, the
DNAzyme cleaved its substrate into two short fragments (S1 and S2). The resulting
fragments had a lower affinity for the DNAzyme than the intact substrate and,
therefore, dissociated from the DNA motor. Consequently, the DNA motor returned
to the closed state and underwent the next cycle between closed and open states.
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