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PNA is peptide nucleic acid, a chemical similar to DNA or RNA but differing in the composition of its "backbone." DNA and RNA have a ribose sugar backbone, whereas PNA's backbone is composed of repeating N-(2-aminoethyl)-glycine units linked by peptide bonds. The various purine and pyrimidine bases are linked to the backbone by methylene carbonyl bonds. PNAs are depicted like peptides, with the N-terminus at the first (left) position and the C-terminus at the right.

Since the backbone of PNA contains no charged phosphate groups, the binding between PNA/DNA strands is stronger than between DNA/DNA strands due to the lack of electrostatic repulsion. Early experiments with homopyrimidine strands (strands consisting of only one repeated pyrimidine base) have shown that the T_m ("melting" temperature) of a 6-base thymine PNA/adenine DNA double helix was 31°C in comparison to an equivalent 6-base DNA/DNA duplex that denatures at a temperature less than 10°C. Mixed base PNA molecules are true mimics of DNA molecules in terms of base-pair recognition. PNA/PNA binding is stronger than PNA/DNA binding.

Synthetic peptide nucleic acid oligomers have been used in recent years in molecular biology procedures, diagnostic assays and antisense therapies. Due to their higher binding strength it is not necessary to design long PNA oligomers for use in these roles, which usually require oligonucleotide probes of 20-25 bases. The main concern of the length of the PNA-oligomers is to guarantee the specificity. PNA oligomers also show greater specificity in binding to complementary DNAs, with a PNA/DNA base mismatch being more destabilizing than a similar mismatch in a DNA/DNA duplex. This binding strength and specificity also applies to PNA/RNA duplexes. PNAs are not easily recognized by either nucleases or proteases, making them resistant to enzymeAn enzyme is a protein, or protein complex, that catalyzes a chemical reaction. Like any catalyst, enzymes work by lowering the activation energy of a reaction, thus allowing the reaction to proceed to its steady state or completion much faster than it ot degradation. PNAs are also stable over a wide pHAlternate uses: see Ph pH (potential (of) hydrogen) is a measure of the concentration of hydrogen ions (H+) in a solution and, therefore, its acidity or alkalinity. The concept was introduced by S. Sorensen in 1909. The p stands for the German potenz mean range. Finally, their uncharged nature should make crossing through cell membraneA component of every biological cell, the cell membrane (or plasma membrane is a thin and structured bilayer of phospholipid and protein molecules that encapsulate the cell. It separates a cell's interior from its surroundings and controls what moves in as easier, which may improve their theraputic value.

It has been hypothesized that the earliest life on EarthEarth also known as the Earth or Terra is the planet on which we live, the third planet outward from the Sun. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harbouring life. The pla may have used PNA as a genetic material due to its extreme robustness, and later transitioned to a DNA/RNA-based system. See RNA world hypothesisThe RNA world hypothesis proposes that RNA was, before the emergence of the first cell, the dominant, and probably the only, form of life. The phrase "The RNA World" was first used by Walter Gilbert in 1986. This hypothesis is supported by RNA's ability t for related information.