Biomedical Engineering Reference
In-Depth Information
within the nanotubes. Therefore, they provide a good starting point for the
fabrication of supramolecular structures and reversible biosensors.
O
O
OH
NH
2
NH
1) SOCl
2
2) H
2
NC
2
H
4
NH
2
hot
HNO
3
O
O
H
OH
NH
2
5
30
29
29
5
30
O
S
O
O
3'
5'
N
O
O
N
O
NH
NH
DNA-5'-thiol
O
O
O
O
O
H
N
O
NH
O
S
5'
3'
N
SMMC
O
32
32
31
31
Figure 5.18
Scheme of SWCNTs covalently bonded to DNA through the SMMC linker.
5.2.1.3
Mechanisms of DNA wrapping and internalisaon of CNTs
A recent manuscript has attempted to disclose the mechanism involved in
the wrapping of DNA around CNTs, showing that the guanine/cytosine (GC)
content was directly correlated to the extent of condensation around CNTs. In
other words, SWCNTs condensed the GC-DNA major groove more easily, while
the adenine/thymine (AT)-DNA major groove appeared too wide for SWCNTs
binding and inally the minor groove did not bind SWCNTs. More precisely,
the interaction between oxidised SWCNTs and GC-DNA was so strong that
it affected not only the DNA's hydration properties but also the whole DNA
structure. Indeed, circular dichroism spectra showed that the condensation
onto CNTs induced a transition of DNA from its native, right-handed “B” form
to an “A” form. Notably, the transition from the B-DNA double helix to the A
form is essential for biological function
57-59
as shown by the existence of the
A form in many protein-DNA complexes, thus suggesting the use of CNTs as
sensors in living cells based on the transition of DNA secondary structure.
In another article, not only the mechanism of DNA wrapping around the
tubes but the whole CNT-DNA complex taken up by cells were explored.
60
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