t-Butyloxy carbonyl (Boc) PNA monomers refer to the amino acids used to synthesize PNA by using the Boc peptide synthesis technology.
PNA is a kind of DNA analog, which retains the DNA basic group and deoxyribose structurally, but the original ribose phosphate skeleton is replaced by an amide bond skeleton similar to peptide bond. Therefore, PNA still follows the principle of base complementary pairing, while the skeleton changes from the original negative to near neutral, which weakens the electrostatic repulsion between double stranded nucleic acids, and greatly improves the binding stability and specificity of LNA and DNA or RNA. Moreover, the amide bond skeleton of PNA is not easy to be hydrolyzed by nuclease and protease, making it stable in vivo and in vitro.
Boc method is a classical solid phase peptide synthesis method, which uses Boc as the protection group of α-amino of amino acid, while benzyl alcohol as the side chain protection group, and trifluoroacetic acid (TFA) is usually used to remove Boc.
The earliest PNA monomers are based on Boc orthogonal protection, which can protect the primary amine and amide in the skeleton. Because the reduction reaction of Schiff base, that is, the reduced glycine ester and the protected aminoacetaldehyde, is only applicable to the PNA monomer synthesized by BOC protection group. However, when removing Boc groups, PNA chains synthesized with it need to use highly corrosive acid reagents such as hydrofluoric acid. These acid reagents are not only easy to corrode the synthesis device but also dangerous.
Using a tetrapeptide as the connecting arm, PNA oligomer can be directly synthesized on the polymer membrane and can be cut off from the membrane. A tetrapeptide synthesized by Boc is used to treat the membrane to reduce the space resistance encountered by PNA probe during hybridization and to provide amino groups that can bind to PNA monomers.