The molecular properties of the phosphodiester backbone that made it the evolutionary choice for the enzymatic replication of genetic information are not well understood. To address this, and to develop new chemical ligation strategies for assembly of biocompatible modified DNA, we have synthesized oligonucleotides containing several structurally and electronically varied artificial linkages. This has yielded a new highly promising ligation method based on amide backbone formation that is chemically orthogonal to CuAAC "click" ligation. A study of kinetics and fidelity of replication through these artificial linkages by primer extension, PCR, and deep sequencing reveals that a subtle interplay between backbone flexibility, steric factors, and ability to hydrogen bond to the polymerase modulates rapid and accurate information decoding. Even minor phosphorothioate modifications can impair the copying process, yet some radical triazole and amide DNA backbones perform surprisingly well, indicating that the phosphate group is not essential. These findings have implications in the field of synthetic biology.

A novel triazole linkage that mimics the phosphodiester backbone in DNA was designed, synthesised and evaluated. Unlike previous work which utilised copper to form a 1,4 triazole linkage in the DNA backbone, a ruthenium catalyst was used to yield a 1,5 triazole. The artificial linkage was incorporated into a DNA backbone via a phosphoramidite building block using solid phase synthesis. The biophysical properties of DNA with a 1,5 triazole linkage in the backbone were evaluated by UV melting and circular dichroism and compared to DNA modified with previously reported 1,4 triazole linkages of various lengths.

Triazole linkages (TLs) are mimics of the phosphodiester bond in oligonucleotides with applications in synthetic biology and biotechnology. Here we report the RuAAC-catalyzed synthesis of a novel 1,5-disubstituted triazole (TL 2 ) dinucleoside phosphoramidite as well as its incorporation into oligonucleotides and compare its DNA polymerase replication competency with other TL analogues. We demonstrate that TL 2 has superior replication kinetics to these analogues and is accurately replicated by polymerases. Derived structure–biocompatibility relationships show that linker length and the orientation of a hydrogen bond acceptor are critical and provide further guidance for the rational design of artificial biocompatible nucleic acid backbones.