Polyamide nucleic acids properties

Recently, introduction of DNA analogous detection systems such as the use of peptide nucleic acid (PNA) technology has attracted considerable attention [10]. The PNAs are synthetic analogues of DNA that hybridise with complementary DNAs or RNAs with high affinity and specificity, essentially because of an uncharged and flexible polyamide backbone. The unique physico-chemical properties of PNAs have led to the development of a variety of research and diagnostic assays where these are used as molecular hybridisation probes [11]. 

The affinity towards a complementary RNA strand can be improved by using peptide nucleic acids (PNAs) [20]. These DNA mimics, in which the nucleic acid bases are linked to a polyamide backbone [21], usually exhibit improved binding properties with a complementary DNA or RNA strand [22]. The use of an excess PNA-DETA adduct 20 in a Tris-HCl buffer (pH 7), in the presence of NaCl and EDTA at 40 °C, resulted in a sequence-selective cleavage of the RNA strand 21... 

The life that we know also uses proteins for the majority of structural and catalytic functions. Proteins are particularly suited for these functions because of the structural properties of polymers of amino acids. The polyamide backbone of proteins is neutral, unlike that of nucleic acids. Further, the backbone has a repeating dipole able to make hydrogen bonds. These structural features are exploited as proteins fold into globular structures, as they promote the formation of stable secondary structures such as alpha helices and beta sheets. 

Another second-generation class of antisense molecules are the peptide nucleic acids, in which the deoxyribose backbone is replaced by polyamide linkages (Fig. 8.6). These molecules have favorable hybridization properties, are very stable in a biological environment, and seem to be nontoxic. They are electrostatically neutral, so solubility and cellular uptake are serious problems. They do not induce RNase H and, therefore, have been used to correct aberrant splicing (18). 

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