3 research outputs found
Ribonucleosides for an Artificially Expanded Genetic Information System
Rearranging hydrogen bonding groups
adds nucleobases to an artificially
expanded genetic information system (AEGIS), pairing orthogonally
to standard nucleotides. We report here a large-scale synthesis of
the AEGIS nucleotide carrying 2-amino-3-nitroÂpyridin-6-one (trivially
Z) via Heck coupling and a hydroÂboration/oxidation sequence.
RiboZ is more stable against epimerization than its 2â˛-deoxyÂribo
analogue. Further, T7 RNA polymerase incorporates ZTP opposite its
WatsonâCrick complement, imidazoÂ[1,2-a]-1,3,5-triazin-4Â(8<i>H</i>)Âone (trivially P), laying grounds for using this âsecond-generationâ
AEGIS Z:P pair to add amino acids encoded by mRNA
Synthesis and Enzymology of 2â˛-Deoxy-7-deazaisoguanosine Triphosphate and Its Complement: A Second Generation Pair in an Artificially Expanded Genetic Information System
As with natural nucleic acids, pairing
between artificial nucleotides
can be influenced by tautomerism, with different placements of protons
on the heterocyclic nucleobase changing patterns of hydrogen bonding
that determine replication fidelity. For example, the major tautomer
of isoguanine presents a hydrogen bonding <i>donor</i>â<i>donor</i>â<i>acceptor</i> pattern complementary
to the <i>acceptor</i>â<i>acceptor</i>â<i>donor</i> pattern of 5-methylisocytosine. However, in its minor
tautomer, isoguanine presents a hydrogen bond <i>donor</i>â<i>acceptor</i>â<i>donor</i> pattern
complementary to thymine. Calculations, crystallography, and physical
organic experiments suggest that this tautomeric ambiguity might be
âfixedâ by replacing the N-7 nitrogen of isoguanine
by a CH unit. To test this hypothesis, we prepared the triphosphate
of 2â˛-deoxy-7-deazaiso-guanosine and used it in PCR to estimate
an effective tautomeric ratio âseenâ by <i>Taq</i> DNA polymerase. With 7-deazaisoguanine, fidelity-per-round was âź92%.
The analogous PCR with isoguanine gave a lower fidelity-per-round
of âź86%. These results confirm the hypothesis with polymerases,
and deepen our understanding of the role of minor groove hydrogen
bonding and proton tautomerism in both natural and expanded genetic
âalphabetsâ, major targets in synthetic biology
Synthesis and Enzymology of 2â˛-Deoxy-7-deazaisoguanosine Triphosphate and Its Complement: A Second Generation Pair in an Artificially Expanded Genetic Information System
As with natural nucleic acids, pairing
between artificial nucleotides
can be influenced by tautomerism, with different placements of protons
on the heterocyclic nucleobase changing patterns of hydrogen bonding
that determine replication fidelity. For example, the major tautomer
of isoguanine presents a hydrogen bonding <i>donor</i>â<i>donor</i>â<i>acceptor</i> pattern complementary
to the <i>acceptor</i>â<i>acceptor</i>â<i>donor</i> pattern of 5-methylisocytosine. However, in its minor
tautomer, isoguanine presents a hydrogen bond <i>donor</i>â<i>acceptor</i>â<i>donor</i> pattern
complementary to thymine. Calculations, crystallography, and physical
organic experiments suggest that this tautomeric ambiguity might be
âfixedâ by replacing the N-7 nitrogen of isoguanine
by a CH unit. To test this hypothesis, we prepared the triphosphate
of 2â˛-deoxy-7-deazaiso-guanosine and used it in PCR to estimate
an effective tautomeric ratio âseenâ by <i>Taq</i> DNA polymerase. With 7-deazaisoguanine, fidelity-per-round was âź92%.
The analogous PCR with isoguanine gave a lower fidelity-per-round
of âź86%. These results confirm the hypothesis with polymerases,
and deepen our understanding of the role of minor groove hydrogen
bonding and proton tautomerism in both natural and expanded genetic
âalphabetsâ, major targets in synthetic biology