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Chapter 5
PNA 3 PNA 5 PNA 6
Slide 1
DNA c3 + DNA c5
Slide 2
DNA c3
Slide 3
DNA c5
Slide 3 DNA c3
60 bases
Figure 5-9: Fluorescence images of PNA slides hybridized with full-matched and mismatched
fluorescent oligonucleotides
The fluorescence pictures (Figure 5-9) shows that these devices fabricated as previously
reported have excellent selectivity. PNA 6 has a sequence totally unrelated to DNA c3 and c5,
and never binds to any of these oligonucleotides (figure 5-9, last picture of every row): this
PNA is used to demonstrate the selectivity towards different sequences. PNAs 3 and 5
recognize their complementary sequence (Figure 5-9, first row, first and second pictures;
second row, first picture; third row, second picture). Moreover, the figure demonstrates that
point mutations can be discriminated with a good selectivity (no signal was visible when
mismatched DNA was used, Figure 5-9, second row, second picture; third row, first picture).
The last row of figure 5-9 shows the images obtained upon hybridization with a long synthetic
oligonucleotides (60mer) including the c1 sequence, in order to simulate a real PCR product.
As it can be seen, the system recognized quite efficiently also this molecule. A signal, in fact,
is produced only where the fullmatch hybrid is formed, while no recognition takes place in the
case of PNA 5 which only differs for one nucleobase, demonstrating that point mutation
discrimination is totally feasible with this system. However, it should be noted that in this
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