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PNA
What is PNA?
An Innovative Raw Material
PNA (Peptide Nucleic Acid), an artificially created DNA analogue, was first invented by Professor Nielsen, Egholm, Berg and Buchardt of the University of Copenhagen, Denmark in 1991.
PNA has a structure in which the phosphate-ribose backbone of DNA is substituted with a peptide-like amide backbone (N-(2-aminoethyl) glycine). So the binding affinity and stability to the target DNA or RNA are greatly increased. Despite the structural change of the backbone, PNA can be used in a variety of applications where DNA can be used because it can make a complementary binding to the target sequence as DNA does.
FEATURES & ADVANTAGES
High binding affinity
PNA has electrically neutral amide backbone. There is no repulsion between the PNA strand and the DNA strand, and PNA has the stronger binding affinity for the target DNA.
High specificity and sensitivity
The difference in binding affinity between perfect match and mismatch of PNA/DNA strands is bigger than DNA/DNA strands. It is easy to discriminate even single nucleotide mismatched sequence.
Chemical/Biological/thermal stability
PNA is quite stable under high temperature or high pH condition. Also, PNA backbone is completely different from DNA’s or RNA’s and is similar to but slightly different from the peptide backbone. So, PNA is stable against enzymes as nuclease or protease.
Independence against salt in hybridization
PNA has stable and strong binding affinity due to its independence against high salt concentration in hybridization.
PNA VS DNA
| Feature | PNA | DNA |
|---|---|---|
| Binding Affinity | At Least 1°C Higher Tm per Base | - |
| Hybridization rate | 100-5000 Times Faster | - |
| Salt concentration in hybridization | Independent | Dependent |
| ΔTm for single nucleotide mismatch | <10°C | <15°C |
| ChemicalStability | Stable | Unstable in Acidic or Basic condition |
| BiologicalStability | Enzyme-Resistant | Degradable by Nuclease |
| Solubility | Moderate(but can be improved by simple modification) | Good |
| General Probe Length | 13-18mer | 25-30mer |
PANAGENE's PNA
PANAGENE has developed its proprietary Bts PNA monomers (Bts; benzothiazole-2-sulfonyl group) and PNA oligo synthesis method using Bts monomers, and has supplied high quality PNA oligos.
Bts group of the Bts PNA monomers not only protects the amine group (NH2) of the monomer but also is self-activated. So, oligo synthesis using Bts monomers does not require a pre-activation step or many coupling reagents. Unlike the conventional synthesis method (using Fmoc PNA monomers), the side reactions such as transacylation which occur during the deprotection process are minimized and mass production of high purity PNA oligo can be achieved at low cost. In addition, it is more economical because it is possible to recover and reuse excess Bts monomers which remains after the coupling reaction.
Chemical Structure of Bts PNA monomer & oligomerization cycle
[Reference]
Hyunil Lee et al. 2007. Peptide Nucleic Acid Synthesis by Novel Amide Formation. Org. Lett. 9 (17), 3291-3293.
Bts vs. Fmoc
| Type | Bts monomer | Fmoc monomer |
|---|---|---|
| Coupling reagent | Not necessary | HATU |
| Mass production | Easy | Difficult |
| Side reaction | <1% | Hard to control(5~10%) |
| Purification | Easy | Difficult |
| Yield | >80% | <40% |
| Cost of synthesis | Low | High |
Fmoc monomer 
