Biology Reference
In-Depth Information
mismatches in a PNA/DNA duplex is much more destabilizing
than a mismatch in a DNA/DNA duplex, thus a PNA-modified
transducer surface can distinguish perfect complementary DNA
strand from one with a single mismatch. It is suggested that the
uncharged nature of PNA is accounted for greater thermal stability
(Natsume
et al
., 2007). The lack of electrostatic repulsion between
the two strands in a PNA/nucleic acid duplex leaves the melting
temperature largely independent of salt concentration. In addition
to greater mismatch discrimination, PNA biosensors have higher
biologicalstabilityandoperationoverawiderangeofhybridization
conditions (compared to their DNA counterparts). Therefore, PNA
probes become attractive oligonucleotide recognition elements in
biosensortechnology(Wang,1998).
16.5.2
Locked Nucleic Acid (LNA)
LNA, also referred as inaccessible RNA, is an RNA analogue
exhibiting C3'-endo conformation similar to the RNA. In LNA, the
furanose ring of the ribose sugar is chemically locked by the
presence of a methylene linkage between 2
oxygen and 4
carbon
of the ribose ring (Fig. 16.12). This linkage locks the pentose in
the 3
-endo conformation found in the A-form DNA and RNA. LNA
has high a
nity toward both DNA and RNA single strands. Due to
its restricted conformation, the base stacking and thermal stability
Figure 16.12.
LNA.
