1. Functionalized Acyclic (l)-Threoninol Nucleic Acid Four-Way Junction with High Stability In Vitro and In Vivo
Anders Märcher, et al. Angew Chem Int Ed Engl. 2022 Jun 13;61(24):e202115275. doi: 10.1002/anie.202115275. Epub 2022 Apr 13.
Oligonucleotides are increasingly being used as a programmable connection material to assemble molecules and proteins in well-defined structures. For the application of such assemblies for in vivo diagnostics or therapeutics it is crucial that the oligonucleotides form highly stable, non-toxic, and non-immunogenic structures. Only few oligonucleotide derivatives fulfil all of these requirements. Here we report on the application of acyclic l-threoninol nucleic acid (aTNA) to form a four-way junction (4WJ) that is highly stable and enables facile assembly of components for in vivo treatment and imaging. The aTNA 4WJ is serum-stable, shows no non-targeted uptake or cytotoxicity, and invokes no innate immune response. As a proof of concept, we modify the 4WJ with a cancer-targeting and a serum half-life extension moiety and show the effect of these functionalized 4WJs in vitro and in vivo, respectively.
2. Nonenzymatic polymerase-like template-directed synthesis of acyclic L-threoninol nucleic acid
Keiji Murayama, Hikari Okita, Takumi Kuriki, Hiroyuki Asanuma Nat Commun. 2021 Feb 5;12(1):804. doi: 10.1038/s41467-021-21128-0.
Evolution of xeno nucleic acid (XNA) world essentially requires template-directed synthesis of XNA polymers. In this study, we demonstrate template-directed synthesis of an acyclic XNA, acyclic L-threoninol nucleic acid (L-aTNA), via chemical ligation mediated by N-cyanoimidazole. The ligation of an L-aTNA fragment on an L-aTNA template is significantly faster and occurs in considerably higher yield than DNA ligation. Both L-aTNA ligation on a DNA template and DNA ligation on an L-aTNA template are also observed. High efficiency ligation of trimer L-aTNA fragments to a template-bound primer is achieved. Furthermore, a pseudo primer extension reaction is demonstrated using a pool of random L-aTNA trimers as substrates. To the best of our knowledge, this is the first example of polymerase-like primer extension of XNA with all four nucleobases, generating phosphodiester bonding without any special modification. This technique paves the way for a genetic system of the L-aTNA world.
3. Formation of i-motifs from acyclic (l)-threoninol nucleic acids
Vipin Kumar, Thuy J D Nguyen, Johan Palmfeldt, Kurt V Gothelf Org Biomol Chem. 2019 Sep 7;17(33):7655-7659. doi: 10.1039/c9ob01220f. Epub 2019 Jul 30.
Acyclic (l)-threoninol nucleic acids ((l)-aTNA) containing poly-cytosines are prepared and investigated at various pH values, revealing the formation of a highly stable structure at lower pH that have the characteristics of an i-motif. Depending on the sequence, the aTNA forms inter-, bi- and intra-molecular i-motif structures. Pyrene was conjugated to aTNA sequences and both monomeric and excimer fluorescence were efficiently quenched by the i-motif structures and thus demonstrated that the aTNA i-motif can serve as a pH switch.
