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Chapter 2<br />

Label-free detection of Single Nucleotide Polymorphisms<br />

(SNPs): PNA Molecular Beacons<br />

In this chapter the application of modified PNAs for SNP detection is shown. PNA beacons<br />

allow to detect complementary DNA sequences without the necessity to label it before or after<br />

PCR amplification. Upon hybridization, in fact, these molecules emit a fluorescence signal<br />

which is highly enhanced if compared to that of the free unhybridized beacon. The probes<br />

here presented were designed in order to recognize a SNP which is diagnostic for the olive<br />

cultivar “Ogliarola Leccese”. Three beacons of different length were synthesized, in order to<br />

test the recognition performances in relation to the PNA length. The application in AE-HPLC,<br />

together with solution assays, allowed to identify the ideal length for specific and efficient<br />

DNA hybridization and to verify the PNA probes performances. After optimization of the<br />

method, the probe was applied to recognize the SNP in a sample of DNA extracted from olive<br />

leaves and amplified by PCR. It has been shown that this methodology can be applied to real<br />

samples.<br />

39

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