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A new artificial nucleic acid analogue,(R)-Am-BuNA was developed with a simplified acyclic(R)-4-amino-butane-1,3-diol phosphodiester backbone.Phosphoramidite monomers of(R)-am-BuNA were incorporated in DNA oligonucleotides(ODNs)and G-quadruplexes.Their thermal stability,conformation change and biological stability were further investigated using UV-melting,circular dichroism(CD)and gel electrophoresis.The results suggested that thermal stability of the duplexes of(R)-am-BuNA modified ODNs and their complementary ODN is highly dependent on the substitution position.Substitution of thymidine at 7 th position in thrombin-binding DNA aptamer(TBA)results in an slightly increase in Tm with no effect on aptamer conformation on CD spectrum in comparison to that of natural G-quadruplex.Further enzymatic experiments with fetal bovine serum(FBS)and snake venom phosphodiesterase(SVPDE)indicated that only single replacement of a(R)-Am-BuNA modified nucleobase greatly inhibited oligonucleotide degradation,which shows their promising applications as capping nucleotides in nucleic acid drug