Biomedical Engineering Reference
In-Depth Information
Fig. 3.5
The global and local structures of the 4-Se-T-DNA (5
0
-G
U
2
0
SeMe
G
T
4Se
ACAC-3
0
)
2
.
(
a
) Superimposition of the duplex structure of the modified DNA (2NSK, 1.5 A resolution, in
cyan
) over the native DNA (1DNS, 2.0 A resolution, in
pink
) with the same P43212 space group.
(
b
) Comparison of the Se-modified (in
green
) and native (in
cyan
) local T4 structures. (
c
)Se-base-
pair structure of T4 A5 with the experimental electron density
Enzymatic incorporation of 4-Se-T into oligonucleotides was also reported
[
58
]. The 4-Se-T triphosphosphate was synthesized by treatment with POCl
3
,
followed by pyrophosphate coupling reaction and then aqueous potassium carbonate
hydrolysis. The synthesized 4-Se-TTP is recognized by DNA polymerase and
incorporated into DNA with high efficiency. It is also noteworthy that by a single
oxygen atom replacement with selenium, the color of TTP (as well as DNA)
has changed from colorless to yellow color, and its maximal UV absorption is
shifted from 267 to 369 nm. Since “Huang” means yellow in Chinese, thus, the
Se-modified TTPs and DNAs are also called Huang nucleotides or Huang DNA.
Huang nucleotides with this unique property will be very useful for color nucleic
acid-based detection, nucleic acid visualization, disease diagnosis, as well as color
nanostructure construction [
58
].
3.4.2.2
2-Selenothymidine
High base-pairing fidelity is crucial for replication to maintain the genetic integrity.
The 2-S-T improvement of PCR accuracy in the presence of isoC/isoG pair [
79
]
encouraged us to further investigate the base-pair fidelity. The 2-Se-T modification
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