XNA ligation using T4 DNA ligase in crowding conditions

Enzymatic synthesis of ligand-bearing oligonucleotides for the development of metal-responsive DNA materials

Metal-mediated artificial base pairs are some of the most promising building blocks for constructing DNA-based supramolecules and functional materials. These base pairs are formed by coordination bonds between ligand-type nucleobases and a bridging metal ion and have been exploited to develop metal-responsive DNA materials and DNA-templated metal arrays. In this review, we provide an overview of methods for the enzymatic synthesis of DNA strands containing ligand-type artificial nucleotides that form metal-mediated base pairs. Conventionally, ligand-bearing DNA oligomers have been synthesized via solid-phase synthesis using a DNA synthesizer. In recent years, there has been growing interest in enzymatic methods as an alternative approach to synthesize ligand-bearing DNA oligomers, because enzymatic reactions proceed under mild conditions and do not require protecting groups. DNA polymerases are used to incorporate ligand-bearing unnatural nucleotides into DNA, and DNA ligases are used to connect artificial DNA oligomers to natural DNA fragments. Template-independent polymerases are also utilized to post-synthetically append ligand-bearing nucleotides to DNA oligomers. In addition, enzymatic replication of DNA duplexes containing metal-mediated base pairs has been intensively studied. Enzymatic methods facilitate the synthesis of DNA strands containing ligand-bearing nucleotides at both internal and terminal positions. Enzymatically synthesized ligand-bearing DNAs have been applied to metal-dependent self-assembly of DNA structures and the allosteric control of DNAzyme activity through metal-mediated base pairing. Therefore, the enzymatic synthesis of ligand-bearing oligonucleotides holds great potential in advancing the development of various metal-responsive DNA materials, such as molecular sensors and machines, providing a versatile tool for DNA supramolecular chemistry and nanotechnology.

Controlled enzymatic synthesis of oligonucleotides

Oligonucleotides are advancing as essential materials for the development of new therapeutics, artificial genes, or in storage of information applications. Hitherto, our capacity to write (i.e., synthesize) oligonucleotides is not as efficient as that to read (i.e., sequencing) DNA/RNA. Alternative, biocatalytic methods for the de novo synthesis of natural or modified oligonucleotides are in dire need to circumvent the limitations of traditional synthetic approaches. This Perspective article summarizes recent progress made in controlled enzymatic synthesis, where temporary blocked nucleotides are incorporated into immobilized primers by polymerases. While robust protocols have been established for DNA, RNA or XNA synthesis is more challenging. Nevertheless, using a suitable combination of protected nucleotides and polymerase has shown promises to produce RNA oligonucleotides even though the production of long DNA/RNA/XNA sequences (>1000 nt) remains challenging. We surmise that merging ligase- and polymerase-based synthesis would help to circumvent the current shortcomings of controlled enzymatic synthesis.

2',3'-Protected Nucleotides as Building Blocks for Enzymatic de novo RNA Synthesis

Besides being a key player in numerous fundamental biological processes, RNA also represents a versatile platform for the creation of therapeutic agents and efficient vaccines. The production of RNA oligonucleotides, especially those decorated with chemical modifications, cannot meet the exponential demand. Due to the inherent limits of solid-phase synthesis and in vitro transcription, alternative, biocatalytic approaches are in dire need to facilitate the production of RNA oligonucleotides. Here, we present a first step towards the controlled enzymatic synthesis of RNA oligonucleotides. We have explored the possibility of a simple protection step of the vicinal cis-diol moiety to temporarily block ribonucleotides. We demonstrate that pyrimidine nucleotides protected with acetals, particularly 2',3'-O-isopropylidene, are well-tolerated by the template-independent RNA polymerase PUP (polyU polymerase) and highly efficient coupling reactions can be achieved within minutes - an important feature for the development of enzymatic de novo synthesis protocols. Even though purines are not equally well-tolerated, these findings clearly demonstrate the possibility of using cis-diol-protected ribonucleotides combined with template-independent polymerases for the stepwise construction of RNA oligonucleotides.

Ligase-mediated synthesis of CuII-responsive allosteric DNAzyme with bifacial 5-carboxyuracil nucleobases

A CuII-responsive allosteric DNAzyme has been developed by introducing bifacial 5-carboxyuracil (caU) nucleobases, which form both hydrogen-bonded caU-A and metal-mediated caU-CuII-caU base pairs. The base sequence was logically designed based on a known RNA-cleaving DNAzyme so that the caU-modified DNAzyme (caU-DNAzyme) can form a catalytically inactive structure containing three caU-A base pairs and an active form with three caU-CuII-caU pairs. The caU-DNAzyme was synthesized by joining short caU-containing fragments with a standard DNA ligase. The activity of caU-DNAzyme was suppressed without CuII, but enhanced 21-fold with the addition of CuII. Furthermore, the DNAzyme activity was turned on and off during the reaction by the addition and removal of CuII ions. Both ligase-mediated synthesis and CuII-dependent allosteric regulation were achieved by the bifacial base pairing properties of caU. This study provides a new strategy for designing stimuli-responsive DNA molecular systems.

Synthesis and chemical transformations of glycol nucleic acid (GNA) nucleosides

Xeno nucleic acids (XNA) are an increasingly important class of hypermodified nucleic acids with great potential in bioorganic chemistry and synthetic biology. Glycol nucleic acid (GNA) is constructed from a three-carbon 1,2-propanediol (propylene glycol) backbone attached to a nucleobase entity, representing the simplest known XNA. This review is intended to present GNA nucleosides from a synthetic chemistry perspective-a perspective that serves as a starting point for biological studies. Therefore this account focuses on synthetic methods for GNA nucleoside synthesis, as well as their postsynthetic chemical transformations. The properties and biological activity of GNA constituents are also highlighted. A literature survey shows four major approaches toward GNA nucleoside scaffold synthesis. These approaches pertain to glycidol ring-opening, Mitsunobu, SN2, and dihydroxylation reactions. The general arsenal of reactions used in GNA chemistry is versatile and encompasses the Sonogashira reaction, Michael addition, silyl-Hilbert-Johnson reaction, halogenation, alkylation, cyclization, Rh-catalyzed N-allylation, Sharpless catalytic dihydroxylation, and Yb(OTf)3-catalyzed etherification. Additionally, various phosphorylation reactions have enabled the synthesis of diverse types of GNA nucleotides, dinucleoside phosphates, phosphordiamidites, and oligos. Furthermore, recent advances in GNA chemistry have resulted in the synthesis of previously unknown redox-active (ferrocenyl) and luminescent (pyrenyl and phenanthrenyl) GNA nucleosides, which are also covered in this review.

Convergent Biocatalytic Mediated Synthesis of siRNA

New technologies are required to combat the challenges faced with manufacturing commercial quantities of oligonucleotide drug substances which are required for treating large patient populations. Herein we report a convergent biocatalytic synthesis strategy for an Alnylam model siRNA. The siRNA chemical structure includes several of the unnatural modifications and conjugations typical of siRNA drug substances. Using Almac's 3-2-3-2 hybrid RNA ligase enzyme strategy that sequentially ligates short oligonucleotide fragments (blockmers), the target siRNA was produced to high purity at 1 mM concentration. Additional strategies were investigated including the use of polynucleotide kinase phosphorylation and the use of crude blockmer starting materials without chromatographic purification. These findings highlight a path toward a convergent synthesis of siRNAs for large-scale manufacture marrying both enzymatic liquid and classical solid-phase synthesis.

Base Modifications of Nucleosides via the Use of Peptide-Coupling Agents, and Beyond

Several naturally occurring purine and pyrimidine nucleosides contain an amide linkage as part of the heterocyclic aglycone. Enolization of the amide and conversion to leaving groups at the amide carbon atom permits base modification by addition-elimination types of processes. Although a number of methods have been developed over the years for accomplishing such conversions, the present Personal Account describes efforts from the Lakshman laboratories. Facile activation of the amido groups in nucleobases can be achieved with peptide-coupling agents. Subsequent reaction with nucleophiles then accomplishes the base modifications. In many cases, the activation and displacement steps can be done as two-step, one-pot processes, whereas in other cases, discrete storable activated nucleosides can be isolated for subsequent displacement reactions. Using such an approach a wide range of nucleoside base modifications is readily achievable. In many instances, mechanistic investigations have been conducted so as to understand the activation process.

Enzymatic Conjugation of Modified RNA Fragments by Ancestral RNA Ligase AncT4_2

Oligonucleotide therapeutics have great potential as a next-generation approach to treating intractable diseases. Large quantities of modified DNA/RNA containing xenobiotic nucleic acids (XNAs) must be synthesized before clinical application. In this study, the ancestral RNA ligase AncT4_2 was designed by ancestral sequence reconstruction (ASR) to perform the conjugation reaction of modified RNA fragments. AncT4_2 had superior properties to native RNA ligase 2 from T4 phage (T4Rnl2), including high productivity, a >2.5-fold-higher turnover number, and >10°C higher thermostability. One remarkable point is the broad substrate selectivity of AncT4_2; the activity of AncT4_2 toward 17 of the modified RNA fragments was higher than that of T4Rnl2. The activity was estimated by measuring the conjugation reaction of two RNA strands, 3'-OH (12 bp) and 5'-PO₄ (12 bp), in which the terminal and penultimate positions of the 3'-OH fragment and the first and second positions of the 5'-PO₄ fragment were substituted by 2'-fluoro, 2'-O-methyl, 2'-O-methoxyethyl, and 2'-H, respectively. The enzymatic properties of AncT4_2 allowed the enzyme to conjugate large quantities of double-stranded RNA coding for patisiran (>400 μM level), which was formed by four RNA fragments containing 2'-OMe-substituted nucleic acids. Structural analysis of modeled AncT4_2 suggested that protein dynamics were changed by mutation to Gly or indel during ASR and that this may positively impact the conjugation of modified RNA fragments with the enzyme. AncT4_2 is expected to be a key biocatalyst in synthesizing RNA therapeutics by an enzymatic reaction. IMPORTANCE RNA therapeutics is one of the next-generation medicines for treating various diseases. Our designed ancestral RNA ligase AncT4_2 exhibited excellent enzymatic properties, such as high thermal stability, productivity, specific activity, and broad substrate selectivity compared to native enzymes. These advantages create the potential for AncT4_2 to be applied in conjugating the modified RNA fragments containing various xenobiotic nucleic acids. In addition, patisiran, a known polyneuropathy therapeutic, could be synthesized from four fragmented oligonucleotides at a preparative scale. Taken together, these findings indicate AncT4_2 could open the door to synthesizing RNA therapeutics by enzymatic reaction at large-scale production.

Nucleic Acids and Their Analogues for Biomedical Applications

Nucleic acids are emerging as powerful and functional biomaterials due to their molecular recognition ability, programmability, and ease of synthesis and chemical modification. Various types of nucleic acids have been used as gene regulation tools or therapeutic agents for the treatment of human diseases with genetic disorders. Nucleic acids can also be used to develop sensing platforms for detecting ions, small molecules, proteins, and cells. Their performance can be improved through integration with other organic or inorganic nanomaterials. To further enhance their biological properties, various chemically modified nucleic acid analogues can be generated by modifying their phosphodiester backbone, sugar moiety, nucleobase, or combined sites. Alternatively, using nucleic acids as building blocks for self-assembly of highly ordered nanostructures would enhance their biological stability and cellular uptake efficiency. In this review, we will focus on the development and biomedical applications of structural and functional natural nucleic acids, as well as the chemically modified nucleic acid analogues over the past ten years. The recent progress in the development of functional nanomaterials based on self-assembled DNA-based platforms for gene regulation, biosensing, drug delivery, and therapy will also be presented. We will then summarize with a discussion on the advanced development of nucleic acid research, highlight some of the challenges faced and propose suggestions for further improvement.

Synthesis of Oligoribonucleotides Containing a 2'-Amino-5'-S-phosphorothiolate Linkage

Oligoribonucleotides containing a photocaged 2′-amino-5′-S-phophorothiolate linkage have potential applications as therapeutic agents and biological probes to investigate the RNA structure and function. We envisioned that oligoribonucleotides containing a 2′-amino-5′-S-phosphorothiolate linkage could provide an approach to identify the general base within catalytic RNAs by chemogenetic suppression. To enable preliminary tests of this idea, we developed synthetic approaches to a dinucleotide, trinucleotide, and oligoribonucleotide containing a photocaged 2′-amino-5′-S-phosphorothiolate linkage. We incorporated the photocaged 2′-amino-5′-S-phosphorothiolate linkage into an oligoribonucleotide substrate for the hepatitis delta virus (HDV) ribozyme and investigated the pH dependence of its cleavage following UV irradiation both in the presence and absence of the ribozyme. The substrate exhibited a pH-rate profile characteristic of the modified linkage but reacted slower when bound to the ribozyme. Cleavage inhibition by the HDV ribozyme could reflect a non-productive ground-state interaction with the modified substrate’s nucleophilic 2′-NH₂ or a poor fit of the modified transition state at the ribozyme’s active site.

Redesigning the Genetic Polymers of Life

Genomes can be viewed as constantly updated memory systems where information propagated in cells is refined over time by natural selection. This process, commonly known as heredity and evolution, has been the sole domain of DNA since the origin of prokaryotes. Now, some 3.5 billion years later, the pendulum of discovery has swung in a new direction, with carefully trained practitioners enabling the replication and evolution of "xeno-nucleic acids" or "XNAs"-synthetic genetic polymers in which the natural sugar found in DNA and RNA has been replaced with a different type of sugar moiety. XNAs have attracted significant attention as new polymers for synthetic biology, biotechnology, and medicine because of their unique physicochemical properties that may include increased biological stability, enhanced chemical stability, altered helical geometry, or even elevated thermodynamics of Watson-Crick base pairing.This Account describes our contribution to the field of synthetic biology, where chemical synthesis and polymerase engineering have allowed my lab and others to extend the concepts of heredity and evolution to synthetic genetic polymers with backbone structures that are distinct from those found in nature. I will begin with a discussion of α-l-threofuranosyl nucleic acid (TNA), a specific type of XNA that was chosen as a model system to represent any XNA system. I will then proceed to discuss advances in organic chemistry that were made to enable the synthesis of gram quantities of TNA phosphoramidites and nucleoside triphosphates, the monomers used for solid-phase and polymerase-mediated TNA synthesis, respectively. Next, I will recount our development of droplet-based optical sorting (DrOPS), a single-cell microfluidic technique that was established to evolve XNA polymerases in the laboratory. This section will conclude with structural insights that have been gained by solving X-ray crystal structures of a laboratory-evolved TNA polymerase and a natural DNA polymerase that functions with general reverse transcriptase activity on XNA templates.The final passage of this Account will examine the role that XNAs have played in synthetic biology by highlighting examples in which engineered polymerases have enabled the evolution of biologically stable affinity reagents (aptamers) and catalysts (XNAzymes) as well as the storage and retrieval of binary information encoded in electronic word and picture file formats. Because these examples provide only a glimpse of what the future may have in store for XNA, I will conclude the Account with my thoughts on how synthetic genetic polymers could help drive new innovations in synthetic biology and molecular medicine.

Site-specific polymerase incorporation of consecutive ligand-containing nucleotides for multiple metal-mediated base pairing

An enzymatic method has been developed for the synthesis of DNA oligomers containing consecutive artificial ligand-type nucleotides. Three hydroxypyridone ligand-containing nucleotides forming Cu^II-mediated unnatural base pairs were continuously incorporated at a pre-specified position by a lesion-bypass Dpo4 polymerase. This enzymatic synthesis was applied to the development of a Cu^II-responsive DNAzyme. Accordingly, this research will open new routes for the construction of metal-responsive DNA architectures that are manipulated by multiple metal-mediated base pairing.

Recent progress in non-native nucleic acid modifications

While Nature harnesses RNA and DNA to store, read and write genetic information, the inherent programmability, synthetic accessibility and wide functionality of these nucleic acids make them attractive tools for use in a vast array of applications.

Stepwise Strategy for One-Pot Synthesis of Single-Stranded DNA Rings from Multiple Short Fragments

Cyclic rings of single-stranded (ss) DNA have various unique properties, but wider applications have been hampered by their poor availability. This paper reports a convenient one-pot method in which these rings are efficiently synthesized by using T4 DNA ligase through convergent cyclization of easily available short DNA fragments. The key to the present method is to separate all the splint oligonucleotides into several sets, and add each set sequentially at an appropriate interval to the solutions containing all the short DNA fragments. Compared with simple one-pot strategies involving simultaneous addition of all the splints at the beginning of the reaction, both the selectivity and the yields of target ssDNA rings are greatly improved. This convergent method is especially useful for preparing large-sized rings that are otherwise hard to obtain. By starting from six short DNA fragments (71-82 nt), prepared by a DNA synthesizer, a ssDNA ring of 452-nt size was synthesized in 35 mol % yield and in high selectivity. Satisfactorily pure DNA rings were obtainable simply by treating the crude products with exonuclease.

Bacterial Cell Display as a Robust and Versatile Platform for Engineering Low-Affinity Ligands and Enzymes

Directed evolution has been remarkably successful at expanding the chemical and functional boundaries of biology. That progress is heavily dependent on the robustness and flexibility of the available selection platforms, given the significant cost to (re)develop a given platform to target a new desired function. Bacterial cell display has a significant track record as a viable strategy for the engineering of mesophilic enzymes, as enzyme activity can be probed directly and free from interference from the cellular milieu, but its adoption has lagged behind other display-based methods. Herein, we report the development of SNAP as a quantitative reporter for bacterial cell display, which enables fast troubleshooting and the systematic development of the display-based selection platform, thus improving its robustness. In addition, we demonstrate that even weak interactions between displayed proteins and nucleic acids can be harnessed for the specific labelling of bacterial cells, allowing functional characterisation of DNA binding proteins and enzymes, thus making it a highly flexible platform for these biochemical functions. Together, this establishes bacterial display as a robust and flexible platform, ideally suited for the systematic engineering of ligands and enzymes needed for XNA molecular biology.

Modified nucleic acids: replication, evolution, and next-generation therapeutics

Modified nucleic acids, also called xeno nucleic acids (XNAs), offer a variety of advantages for biotechnological applications and address some of the limitations of first-generation nucleic acid therapeutics. Indeed, several therapeutics based on modified nucleic acids have recently been approved and many more are under clinical evaluation. XNAs can provide increased biostability and furthermore are now increasingly amenable to in vitro evolution, accelerating lead discovery. Here, we review the most recent discoveries in this dynamic field with a focus on progress in the enzymatic replication and functional exploration of XNAs.

Allosteric Regulation of DNAzyme Activities through Intrastrand Transformation Induced by Cu(II)-Mediated Artificial Base Pairing

Allosteric regulation is gaining increasing attention as a basis for the production of stimuli-responsive materials in many research areas including DNA nanotechnology. We expected that metal-mediated artificial base pairs, consisting of ligand-type nucleotides and a bridging metal ion, could serve as allosteric units that regulate the function of DNA molecules. In this study, we established a rational design strategy for developing Cu^II-responsive allosteric DNAzymes by incorporating artificial hydroxypyridone ligand-type nucleotides (H) that form a Cu^II-mediated base pair (H-Cu^II-H). We devised a new enzymatic method using a standard DNA polymerase and a ligase to prepare DNA strands containing H nucleotides. Previously reported DNAzymes were modified by introducing a H-H pair into the stem region, and the stem-loop sequences were altered so that the structure becomes catalytically inactive in the absence of Cu^II ions. The formation of a H-Cu^II-H base pair triggers intrastrand transformation from the inactive to the active structure, enabling allosteric regulation of the DNAzyme activity in response to Cu^II ions. The activity of the H-modified DNAzyme was reversibly switched by the addition and removal of Cu^II ions under isothermal conditions. Similarly, by incorporating a H-Cu^II-H pair into an in vitro-selected Ag^I-dependent DNAzyme, we have developed a DNAzyme that exhibits an AND logic-gate response to Cu^II and Ag^I ions. The rational design strategy and the easy enzymatic synthetic method presented here provide a versatile way to develop a variety of metal-responsive allosteric DNA materials, including molecular machines and logic circuits, based on metal-mediated artificial base pairing.

Effective Characterization of DNA Ligation Kinetics by High-Resolution Melting Analysis

High-resolution melting (HRM) analysis has been improved and applied for the first time to quantitative analysis of enzymatic reactions. By using the relative ratios of peak intensities of substrates and products, the quantitativity of conventional HRM analysis has been improved to allow detailed kinetic analysis. As an example, the ligation of sticky ends through the action of T4 DNA ligase has been kinetically analyzed, with comprehensive data on substrate specificity and other properties having been obtained. For the first time, the kinetic parameters (k_obs and apparent K_m ) of sticky-end ligation were obtained for both fully matched and mismatched sticky ends. The effect of ATP concentration on sticky-end ligation was also investigated. The improved HRM method should also be applicable to versatile DNA-transforming enzymes, because the only requirement is that the products have T_m values different enough from the substrates.

Reprint of: Non Canonical Genetic Material

To increase the scope of natural biosystem, nucleic acids have been intensively modified. One direction includes the development of a synthetic alternative to the native DNA and RNA, denoted Xenobiotic nucleic acids (XNAs) that are able to store and transfer genetic information either by base-modification or backbone-modification. Another line of research aims to develop alternative third base pair additional to natural A:T and G:C. These unnatural base pairs (UBPs) can store increased information content encoded in three base pairs. This review outlines the recent progress made towards XNA and UBP applications as new components of the genomic DNA as well as biostable aptamers. New achievements in the replacement of a bacterial genome by unnatural non-canonical nucleotides are also described.

Rational design of an XNA ligase through docking of unbound nucleic acids to toroidal proteins

Xenobiotic nucleic acids (XNA) are nucleic acid analogues not present in nature that can be used for the storage of genetic information. In vivo XNA applications could be developed into novel biocontainment strategies, but are currently limited by the challenge of developing XNA processing enzymes such as polymerases, ligases and nucleases. Here, we present a structure-guided modelling-based strategy for the rational design of those enzymes essential for the development of XNA molecular biology. Docking of protein domains to unbound double-stranded nucleic acids is used to generate a first approximation of the extensive interaction of nucleic acid processing enzymes with their substrate. Molecular dynamics is used to optimise that prediction allowing, for the first time, the accurate prediction of how proteins that form toroidal complexes with nucleic acids interact with their substrate. Using the Chlorella virus DNA ligase as a proof of principle, we recapitulate the ligase's substrate specificity and successfully predict how to convert it into an XNA-templated XNA ligase.

Ligase-Mediated Threose Nucleic Acid Synthesis on DNA Templates

Ligases are a class of enzymes that catalyze the formation of phosphodiester bonds between an oligonucleotide donor with a 5' terminal phosphate and an oligonucleotide acceptor with a 3' terminal hydroxyl group. Here, we wished to explore the substrate specificity of naturally occurring DNA and RNA ligases to determine whether the molecular recognition of these enzymes is sufficiently general to synthesize alternative genetic polymers with backbone structures that are distinct from those found in nature. We chose threose nucleic acid (TNA) as a model system, as TNA is known to be biologically stable and capable of undergoing Darwinian evolution. Enzyme screening and reaction optimization identified several ligases that can recognize TNA as either the donor or acceptor strand with DNA. Less discrimination occurs on the acceptor strand indicating that the determinants of substrate specificity depend primarily on the composition of the donor strand. Remarkably, T3 and T7 ligases were able to join TNA homopolymers together, which is surprising given that the TNA backbone is one atom shorter than that of DNA. In this reaction, the base composition of the ligation junction strongly favors the formation of A-T and A-G linkages. We suggest that these results will enable the assembly of TNA oligonucleotides of lengths beyond what is currently possible by solid-phase synthesis and provide a starting point for further optimization by directed evolution.

Enzymatic Synthesis of Backbone-Modified Oligonucleotides Using T4 DNA Ligase

T4 DNA ligase in high concentrations of certain crowding agents and cosolutes catalyzes the synthesis of a series of backbone-modified oligonucleotides that are difficult to obtain chemically. Backbone-modified nucleic acids are often enzymatically and chemically more stable, making them interesting as potential diagnostic or therapeutic agents, as a biosafety tool, or in nanotechnology. In this article, we describe a small-scale experiment to probe the efficiency of the ligation reaction of modified oligonucleotides in the presence of 3 M betaine and 10% PEG 8000, followed by large-scale ligation with subsequent isolation of the ligated oligonucleotide. The correct product formation can be verified using denaturing polyacrylamide gel electrophoresis and mass spectrometry. © 2019 by John Wiley & Sons, Inc.

Non canonical genetic material

To increase the scope of natural biosystem, nucleic acids have been intensively modified. One direction includes the development of a synthetic alternative to the native DNA and RNA, denoted Xenobiotic nucleic acids (XNAs) that are able to store and transfer genetic information either by base-modification or backbone-modification. Another line of research aims to develop alternative third base pair additional to natural A:T and G:C. These unnatural base pairs (UBPs) can store increased information content encoded in three base pairs. This review outlines the recent progress made towards XNA and UBP applications as new components of the genomic DNA as well as biostable aptamers. New achievements in the replacement of a bacterial genome by unnatural non-canonical nucleotides are also described.

A simple and isothermal ligase-based amplification approach based on a ligation-activated cleavage reaction

We develop a simple and isothermal ligase-based cyclic amplification approach for the sensitive detection of polynucleotide kinase, DNA, proteins and ATP.