Beyond G-Quadruplexes—The Effect of Junction with Additional Structural Motifs on Aptamers Properties

G-quadruplexes constitute an important type of nucleic acid structure, which can be found in living cells and applied by cell machinery as pivotal regulatory elements. Importantly, robust development of SELEX technology and modern, nucleic acid-based therapeutic strategies targeted towards various molecules have also revealed a large group of potent aptamers whose structures are grounded in G-quadruplexes. In this review, we analyze further extension of tetraplexes by additional structural elements and investigate whether G-quadruplex junctions with duplex, hairpin, triplex, or second G-quadruplex motifs are favorable for aptamers stability and biological activity. Furthermore, we indicate the specific and pivotal role of the G-quadruplex domain and the additional structural elements in interactions with target molecules. Finally, we consider the potency of G-quadruplex junctions in future applications and indicate the emerging research area that is still waiting for development to obtain highly specific and effective nucleic acid-based molecular tools.

Single-molecule fluorescence detection of a tricyclic nucleoside analogue

Fluorescent nucleobase surrogates capable of Watson–Crick hydrogen bonding are essential probes of nucleic acid structure and dynamics, but their limited brightness and short absorption and emission wavelengths have rendered them...

Native de novo structural determinations of non-canonical nucleic acid motifs by X-ray crystallography at long wavelengths

Obtaining phase information remains a formidable challenge for nucleic acid structure determination. The introduction of an X-ray synchrotron beamline designed to be tunable to long wavelengths at Diamond Light Source has opened the possibility to native de novo structure determinations by the use of intrinsic scattering elements. This provides opportunities to overcome the limitations of introducing modifying nucleotides, often required to derive phasing information. In this paper, we build on established methods to generate new tools for nucleic acid structure determinations. We report on the use of (i) native intrinsic potassium single-wavelength anomalous dispersion methods (K-SAD), (ii) use of anomalous scattering elements integral to the crystallization buffer (extrinsic cobalt and intrinsic potassium ions), (iii) extrinsic bromine and intrinsic phosphorus SAD to solve complex nucleic acid structures. Using the reported methods we solved the structures of (i) Pseudorabies virus (PRV) RNA G-quadruplex and ligand complex, (ii) PRV DNA G-quadruplex, and (iii) an i-motif of human telomeric sequence. Our results highlight the utility of using intrinsic scattering as a pathway to solve and determine non-canonical nucleic acid motifs and reveal the variability of topology, influence of ligand binding, and glycosidic angle rearrangements seen between RNA and DNA G-quadruplexes of the same sequence.

Discovery, Design, Synthesis, and Application of Nucleoside/Nucleotides

For decades, nucleosides and nucleotides have formed the cornerstone of antiviral, antiparasitic and anticancer therapeutics and have been used as tools in exploring nucleic acid structure and function [...]