A non-empirical chromophoric interpretation of CD spectra of DNA G-quadruplex structures

Strategy for modeling higher-order G-quadruplex structures recalcitrant to NMR determination

Guanine-rich nucleic acids can form intramolecularly folded four-stranded structures known as G-quadruplexes (G4s). Traditionally, G4 research has focused on short, highly modified DNA or RNA sequences that form well-defined homogeneous compact structures. However, the existence of longer sequences with multiple G4 repeats, from proto-oncogene promoters to telomeres, suggests the potential for more complex higher-order structures with multiple G4 units that might offer selective drug-targeting sites for therapeutic development. These larger structures present significant challenges for structural characterization by traditional high-resolution methods like multi-dimensional NMR and X-ray crystallography due to their molecular complexity. To address this current challenge, we have developed an integrated structural biology (ISB) platform, combining experimental and computational methods to determine self-consistent molecular models of higher-order G4s (xG4s). Here we outline our ISB method using two recent examples from our lab, an extended c-Myc promoter and long human telomere G4 repeats, that highlights the utility and generality of our approach to characterizing biologically relevant xG4s.

N-methyl mesoporphyrin IX (NMM) as electrochemical probe for detection of guanine quadruplexes

G-quadruplexes (G4) are stable alternative secondary structures of nucleic acids. With increasing understanding of their roles in biological processes and their application in bio- and nanotechnology, the exploration of novel methods for the analysis of these structures is becoming important. In this work, N-methyl mesoporphyrin IX (NMM) was used as a voltammetric probe for an easy electrochemical detection of G4s. Cyclic voltammetry on a hanging mercury drop electrode (HMDE) was used to detect NMM with a limit of detection (LOD) of 40 nM. Characteristic reduction signal of NMM was found to be substantially higher in the presence of G4 oligodeoxynucleotides (ODNs) than in the presence of single- or double-stranded ODNs and even ODNs susceptible to form G4s but in their unfolded, single-stranded forms. Gradual transition from unstructured single strand to G4, induced by increasing concentrations of the G4 stabilizing K+ ions, was detected by an electrochemical method for the first time. All obtained results were supported by circular dichroism spectroscopy. This work expands on the concept of electrochemical probes utilization in DNA secondary structure recognition and offers a proof of principle that can be potentially employed in the development of novel electroanalytical methods for nucleic acid structure studies.

Polymeric integration of structure-switching aptamers on transistors for histamine sensing

Aptamers that undergo large conformational rearrangements at the surface of electrolyte-gated field-effect transistor (EG-FETs)-based biosensors can overcome the Debye length limitation in physiological high ionic strength environments. For the sensitive detection of small molecules, carbon nanotubes (CNTs) that approach the dimensions of analytes of interest are promising channel materials for EG-FETs. However, functionalization of CNTs with bioreceptors using frequently reported surface modification strategies (e.g., π-π stacking), requires highly pristine CNTs deposited through methods that are incompatible with low-cost fabrication methods and flexible substrates. In this work, we explore alternative non-covalent surface chemistry to functionalize CNTs with aptamers. We harnessed the adhesive properties of poly-D-lysine (PDL), to coat the surface of CNTs and then grafted histamine-specific DNA aptamers electrostatically in close proximity to the CNT semiconducting channel. The layer-by-layer assembly was monitored by complementary techniques such as X-ray photoelectron spectroscopy, optical waveguide lightmode spectroscopy, and fluorescence microscopy. Surface characterization confirmed histamine aptamer integration into PDL-coated CNTs and revealed ∼5-fold higher aptamer surface coverage when using CNT networks with high surface areas. Specific aptamers assembled on EG-CNTFETs enabled histamine detection in undiluted high ionic strength solutions in the concentration range of 10 nM to 100 μM. Sequence specificity was demonstrated via parallel measurements with control EG-CNTFETs functionalized with scrambled DNA. Histamine aptamer-modified EG-CNTFETs showed high selectivity vs. histidine, the closest structural analog and precursor to histamine. Taken together, these results implied that target-specific aptamer conformational changes on CNTs facilitate signal transduction, which was corroborated by circular dichroism spectroscopy. Our work suggests that layer-by-layer polymer chemistry enables integration of structure-switching aptamers into flexible EG-CNTFETs for small-molecule biosensing.

A Guanosine-Derived Antitumor Supramolecular Prodrug

The prodrug strategy for its potential to enhance the pharmacokinetic and/or pharmacodynamic properties of drugs, especially chemotherapeutic agents, has been widely recognized as an important means to improve therapeutic efficiency. Irinotecan's active metabolite, 7-ethyl-10-hydroxycamptothecin (SN38), a borate derivative, was incorporated into a G-quadruplex hydrogel (GB-SN38) by the ingenious and simple approach. Drug release does not depend on carboxylesterase, thus bypassing the side effects caused by ineffective activation, but specifically responds to the ROS-overexpressed tumor microenvironment by oxidative hydrolysis of borate ester that reduces serious systemic toxicity from nonspecific biodistribution of SN38. Comprehensive spectroscopy was used to define the structural and physicochemical characteristics of the drug-loaded hydrogel. The GB-SN38 hydrogel's high level of biosafety and notable tumor-suppressive properties were proven in in vitro and in vivo tests.

Best method to determine DNA G-quadruplex folding: The 1H-13C HSQC NMR experiment

NMR spectroscopy is the major method for G-quadruplex structure determination under physiologically relevant solution conditions. Unlike duplex B-DNA, in which all nucleotides adopt an anti glycosidic conformation, the core tetrad-guanines in a G-quadruplex can adopt anti or syn glycosidic conformation depending on the folding structure. An experimental method that can clearly and unambiguously determine syn and anti tetrad-Gs in a G-quadruplex is highly desirable and necessary. In the present study, we exploit the advantages of the 1H-13C HSQC experiment to determine tetrad-G's glycosidic conformation and thus folding topology of G-quadruplexes. We use several examples to demonstrate the clear and straightforward determination of the guanine glycosidic conformations and G-quadruplex folding structures. Moreover, 1H-13C HSQC data can readily identify adenine H2 resonances as well as determine unusual syn conformation in loop and flanking sequences, a challenging task by standard 2D NOESY.

Structure, Topology, and Stability of Multiple G-quadruplexes in Long Telomeric Overhangs

Telomeres and their single stranded overhangs gradually shorten with successive cell divisions, as part of the natural aging process, but can be elongated by telomerase, a nucleoprotein complex which is activated in the majority of cancers. This prominent implication in cancer and aging has made the repetitive telomeric sequences (TTAGGG repeats) and the G-quadruplex structures that form in their overhangs the focus of intense research in the past several decades. However, until recently most in vitro efforts to understand the structure, stability, dynamics, and interactions of telomeric overhangs had been focused on short sequences that are not representative of longer sequences encountered in a physiological setting. In this review, we will provide a broad perspective about telomeres and associated factors, and introduce the agents and structural characteristics involved in organizing, maintaining, and protecting telomeric DNA. We will also present a summary of recent research performed on long telomeric sequences, nominally defined as those that can form two or more tandem G-quadruplexes, i.e., which contain eight or more TTAGGG repeats. Results of experimental studies using a broad array of experimental tools, in addition to recent computational efforts will be discussed, particularly in terms of their implications for the stability, folding topology, and compactness of the tandem G-quadruplexes that form in long telomeric overhangs.

G-quadruplex is critical to epigenetic activation of the lncRNA HOTAIR in cancer cells

The cancer-promoting lncRNA HOTAIR has multiple isoforms. Which isoform of HOTAIR accounts for its expression and functions in cancer is unknown. Unlike HOTAIR's canonical intergenic isoform NR_003716 (HOTAIR-C), the novel isoform NR_047517 (HOTAIR-N) forms an overlapping antisense transcription locus with HOXC11. We identified HOTAIR-N as the dominant isoform that regulates the gene expression programs and networks for cell proliferation, survival, and death in cancer cells. The CpG island in the HOTAIR-N promoter was marked with epigenetic markers for active transcription. We identified a G-quadruplex (G4) motif rich region in the HOTAIR-N CpG island. Our findings indicate that G4s in HOTAIR-N CpG island is critical for expression of HOTAIR-N in cancer cells. Disruption of G4 may represent a novel therapeutic approach for cancer. The transcriptomes regulated by HOTAIR-N and Bloom in cancer cells as provided herein are important resources for the exploration of lncRNA, DNA helicases, and G4 in cancer.

Probing naphthalene diimide and 3-hydroxypropylphosphate as end-conjugating moieties for improved thrombin binding aptamers: Structural and biological effects

The limitations associated with the in vivo use of the thrombin binding aptamer (TBA or TBA15) have dramatically stimulated the search of suitable chemically modified analogues in order to discover effective and reversible inhibitors of thrombin activity. In this context, we previously proposed cyclic and pseudo-cyclic TBA analogues with improved stability that proved to be more active than the parent aptamer. Herein, we have investigated a novel library of TBA derivatives carrying naphthalene diimide (NDI) moieties at the 3'- or 5'-end. In a subset of the investigated oligonucleotides, additional 3-hydroxypropylphosphate (HPP) groups were introduced at one or both ends of the TBA sequence. Evaluation of the G-quadruplex thermal stability, serum nuclease resistance and in vitro anticoagulant activity of the new TBA analogues allowed rationalizing the effect of these appendages on the activity of the aptamer on the basis of their relative position. Notably, most of the different TBA analogues tested were more potent thrombin inhibitors than unmodified TBA. Particularly, the analogue carrying an NDI group at the 5'-end and an HPP group at the 3'-end, named N-TBA-p, exhibited enhanced G-quadruplex thermal stability (ΔTm + 14° C) and ca. 10-fold improved nuclease resistance in serum compared to the native aptamer. N-TBA-p also induced prolonged and dose-dependent clotting times, showing a ca. 11-fold higher anticoagulant activity compared to unmodified TBA, as determined by spectroscopic methods. Overall, N-TBA-p proved to be in vitro a more efficient thrombin inhibitor than all the best ones previously investigated in our group. Its interesting features, associated with its easy preparation, make it a very promising candidate for future in vivo studies.

Guidelines for G-quadruplexes: I. In vitro characterization

Besides the well-known DNA double-helix, non-canonical nucleic acid structures regulate crucial biological activities. Among these oddities, guanine-rich DNA sequences can form unusual four-stranded secondary structures called G-quadruplexes (G4s). G4-prone sequences have been found in the genomes of most species, and G4s play important roles in essential processes such as transcription, replication, genome integrity and epigenetic regulation. Here, we present a short overview of G-quadruplexes followed by a detailed description of the biophysical and biochemical methods used to characterize G4s in vitro. The principles, experimental details and possible shortcomings of each method are discussed to provide a comprehensive view of the techniques used to study these structures. We aim to provide a set of guidelines for standardizing research on G-quadruplexes; these guidelines are not meant to be a dogmatic set of rules, but should rather provide useful information on the methods currently used to study these fascinating motifs.

Resolving a guanine-quadruplex structure in the SARS-CoV-2 genome through circular dichroism and multiscale molecular modeling

The genome of SARS-CoV-2 coronavirus is made up of a single-stranded RNA fragment that can assume a specific secondary structure, whose stability can influence the virus's ability to reproduce. Recent studies have identified putative guanine quadruplex sequences in SARS-CoV-2 genome fragments that are involved in coding for both structural and non-structural proteins. In this contribution, we focus on a specific G-rich sequence referred to as RG-2, which codes for the non-structural protein 10 (Nsp10) and assumes a guanine-quadruplex (G4) arrangement. We provide the secondary structure of RG-2 G4 at atomistic resolution by molecular modeling and simulation, validated by the superposition of experimental and calculated electronic circular dichroism spectra. Through both experimental and simulation approaches, we have demonstrated that pyridostatin (PDS), a widely recognized G4 binder, can bind to and stabilize RG-2 G4 more strongly than RG-1, another G4 forming sequence that was previously proposed as a potential target for antiviral drug candidates. Overall, this study highlights RG-2 as a valuable target to inhibit the translation and replication of SARS-CoV-2, paving the way towards original therapeutic approaches against emerging RNA viruses.

G-quadruplex DNA binding properties of novel nickel Schiff base complexes with four pendant groups

Three new nickel Schiff base complexes were prepared using a two-step procedure that involves initial selective dialkylation of 2,4,6-trihydroxybenzaldehyde, followed by reaction with 1,2-phenylenediamine and nickel(II) acetate. Each of the complexes possessed the same Schiff base core but differed in the identity of the four pendant groups. All complexes were characterised by microanalysis, NMR spectroscopy and ESI mass spectrometry. In addition, two of the complexes were also characterised in the solid state using X-ray crystallography, which confirmed the presence of a square planar geometry around the metal ion. The DNA binding properties of the three nickel complexes with double stranded DNA and a range of G-quadruplex DNA structures were explored using ESI mass spectrometry, CD spectroscopy, UV melting curves, Fluorescence Resonance Energy Transfer (FRET) assays, Fluorescent Indicator Displacement (FID) assays and molecular docking studies. These techniques confirmed the ability of the three nickel complexes to bind to most of the DNA molecules examined, as well as stabilise the latter in several instances. In addition, the results of these investigations provided evidence that pendant groups with morpholine rings generally reduced DNA binding behaviour, whilst pendants featuring piperidine ring systems attached to the Schiff base core by three and not two methylene linkers often showed the greatest extent of binding or DNA stabilisation.

Do conformational changes contribute to the surface plasmon resonance signal?

Surface plasmon resonance (SPR)-based biosensors are widely used instruments for characterizing molecular interactions. In theory the SPR signal depends only on mass changes for interacting molecules of same chemical nature. Whether conformational changes of interacting molecules also contribute to the SPR signal is still a subject of lively debates. Works have been published claiming that conformational changes were detected but all factors contributing to the SPR signal were not carefully considered, in addition to often using no or improper controls. In the present work we used a very well-characterized oligonucleotide, the thrombin-binding DNA aptamer (TBA), which upon binding of potassium ions folds into a two G-tetrad antiparallel G-quadruplex structure. All terms contributing to the maximal expected SPR response, R_max, in particular the refractive index increment, RII, of both partners and the fraction of immobilized TBA target available, c_a, were experimentally assessed. The resulting R_max was then compared to the maximal experimental SPR response for potassium ions binding to TBA using appropriate controls. Regardless how the RIIs were measured, by SPR or refractometry, and how much TBA available for interacting with potassium ions was considered, the theoretical and the experimental SPR responses never matched, the former being always lower than the latter. Using a straightforward experimental model system and by thoroughly taking into account all contributing factors we therefore conclude that conformational changes can indeed contribute to the measured SPR signal.

Computing the electronic circular dichroism spectrum of DNA quadruple helices of different topology: A critical test for a generalized excitonic model based on a fragment diabatization

In this study, we exploit a recently developed fragment diabatization-based excitonic model, FrDEx, to simulate the electronic circular dichroism (ECD) spectra of three guanine-rich DNA sequences arranged in guanine quadruple helices with different topologies: thrombin binding aptamer (antiparallel), c-Myc promoter (parallel), and human telomeric sequence (3+1 hybrid). Starting from time-dependent density functional theory (TD-DFT) calculations with the M052X functional, we apply our protocol to parameterize the FrDEX Hamiltonian, which accounts for electron density overlap and includes both the coupling with charge transfer transitions and the effect of the surrounding bases on the local excitation of each chromophore. The TD-DFT/M052X spectral shapes are in good agreement with the experimental ones, the main source of discrepancy being related to the intrinsic error on the computed transition energies of guanine monomer. FrDEx spectra are fairly close to the reference TD-DFT ones, allowing a significant advance with respect to a more standard excitonic Hamiltonian. We also show that the ECD spectra are sensitive to the inclusion of the inner K + $$ {}^{+} $$ cation in the calculation.

A simple method for fabricating drugs containing a cis-o-diol structure into guanosine-based supramolecular hydrogels for drug delivery

Supramolecular hydrogels are attractive biomaterials for local drug delivery owing to their excellent self-healing, injectable, biodegradable, and biocompatible properties. However, traditional drug-loading approaches based on non-covalent encapsulation and covalent bonding have shown problems such as rapid or difficult drug release, complex reaction processes, low reaction efficiency, and decreased drug activity. Therefore, there is a need to find a simple and efficient method to load drugs into hydrogels, which possess stable drug release ability without impairing drug efficacy. In this study, we introduce dynamic borate ester bonds via a simple one-pot method to load cis-o-diol-containing drugs into guanosine (G)-based supramolecular hydrogels. The experimental results confirm that the dynamic covalent borate ester bonds are formed based on the cis-o-diol groups of the drug and the G in these hydrogels. Meanwhile, the as-prepared G-based hydrogels not only possess self-healing properties and injectability but also have satisfactory biodegradability and biocompatibility. Additionally, the drug can be released from the G-based hydrogel according to the pH-responsive cleavage of the borate ester bonds without affecting drug activity. Overall, these results indicate that the simple one-pot method of utilizing the dynamic borate bond can provide a valuable reference for the design of hydrogel dosage forms.

Mapping DNA Conformations Using Single-Molecule Conductance Measurements

DNA is an attractive material for a range of applications in nanoscience and nanotechnology, and it has recently been demonstrated that the electronic properties of DNA are uniquely sensitive to its sequence and structure, opening new opportunities for the development of electronic DNA biosensors. In this report, we examine the origin of multiple conductance peaks that can occur during single-molecule break-junction (SMBJ)-based conductance measurements on DNA. We demonstrate that these peaks originate from the presence of multiple DNA conformations within the solutions, in particular, double-stranded B-form DNA (dsDNA) and G-quadruplex structures. Using a combination of circular dichroism (CD) spectroscopy, computational approaches, sequence and environmental controls, and single-molecule conductance measurements, we disentangle the conductance information and demonstrate that specific conductance values come from specific conformations of the DNA and that the occurrence of these peaks can be controlled by controlling the local environment. In addition, we demonstrate that conductance measurements are uniquely sensitive to identifying these conformations in solutions and that multiple configurations can be detected in solutions over an extremely large concentration range, opening new possibilities for examining low-probability DNA conformations in solutions.

Identification and characterisation of G-quadruplex DNA-forming sequences in the Pseudomonas aeruginosa genome

A number of Gram-negative bacteria such as Pseudomonas aeruginosa are becoming resistant to front-line antibiotics. Consequently, there is a pressing need to find alternative bio-molecular targets for the development of new drugs. Since non-canonical DNA structures such as guanine-quadruplexes (G4s) have been implicated in regulating transcription, we were interested in determining whether there are putative quadruplex-forming sequences (PQS) in the genome of Pseudomonas aeruginosa. Using bioinformatic tools, we screened 36 genes potentially relevant to drug resistance for the presence of PQS and 10 of these were selected for biophysical characterisation (i.e. circular dichroism and thermal difference UV/Vis spectroscopy). These studies showed that three of these G-rich sequences (linked to murE, ftsB and mexC genes) form stable guanine-quadruplexes which were studied by NMR spectroscopy; detailed analysis of one of the sequences (mexC) confirmed that it adopts a two-quartet antiparallel quadruplex structure in the presence of K⁺ ions. We also show by FRET melting assays that small molecules can stabilise these three new G4 DNA structures under physiological conditions. These initial results could be of future interest in the development of new antibiotics with alternative bio-molecular targets which in turn would help tackle antimicrobial resistance.

An atypical RNA quadruplex marks RNAs as vectors for gene silencing

The addition of poly(UG) ('pUG') repeats to 3' termini of mRNAs drives gene silencing and transgenerational epigenetic inheritance in the metazoan Caenorhabditis elegans. pUG tails promote silencing by recruiting an RNA-dependent RNA polymerase (RdRP) that synthesizes small interfering RNAs. Here we show that active pUG tails require a minimum of 11.5 repeats and adopt a quadruplex (G4) structure we term the pUG fold. The pUG fold differs from known G4s in that it has a left-handed backbone similar to Z-RNA, no consecutive guanosines in its sequence, and three G quartets and one U quartet stacked non-sequentially. The compact pUG fold binds six potassium ions and brings the RNA ends into close proximity. The biological importance of the pUG fold is emphasized by our observations that porphyrin molecules bind to the pUG fold and inhibit both gene silencing and binding of RdRP. Moreover, specific 7-deaza substitutions that disrupt the pUG fold neither bind RdRP nor induce RNA silencing. These data define the pUG fold as a previously unrecognized RNA structural motif that drives gene silencing. The pUG fold can also form internally within larger RNA molecules. Approximately 20,000 pUG-fold sequences are found in noncoding regions of human RNAs, suggesting that the fold probably has biological roles beyond gene silencing.

Assessing the Potential for DNA Quadruplex Formation in the Predatory Bacterium Bdellovibrio bacteriovorus

During its life cycle, the predatory bacterium Bdellovibrio bacteriovorus switches between an attack and a growth phase, each of which is characterized by a distinct pattern of gene expression. Twenty-one potential G-quadruplex-forming sequences (PQFS) have been identified in the Bdellovibrio genome. These G-rich sequences are prevalent within open reading frames and nearly evenly distributed between the template and the coding strand, suggesting that they could play a role in gene expression and life cycle switching. Published transcriptomic data show that the genes nearest these sequences are not (de)activated together during the same phases of the life cycle. We explored the biophysical properties of three identified PQFS using circular dichroism (CD) spectroscopy and gel electrophoresis and demonstrated that all three sequences fold into stable unimolecular quadruplexes with distinct topologies. In the presence of their complementary strands, each forms an equilibrium mixture of duplex and quadruplex in which quadruplex formation is favored at higher temperatures. Once the quadruplexes are folded, they are slow to form a duplex when the complementary strand is added, with one sequence requiring the equivalent of many Bdellovibrio lifetimes to do so. Using a variety of cosolutes, we showed that molecular crowding mimicking cellular conditions stabilizes the quadruplex structures and induces structural transitions to the parallel topology regardless of the original topology. Taken together, these experiments suggest that Bdellovibrio PQFS are capable of forming quadruplexes in vivo and thereby playing a role in gene expression.

Discriminating between Parallel, Anti-Parallel and Hybrid G-Quadruplexes: Mechanistic Details on Their Binding to Small Molecules

G-quadruplexes (G4) are now extensively recognised as a peculiar non-canonical DNA geometry that plays a prime importance role in processes of biological relevance whose number is increasing continuously. The same is true for the less-studied RNA G4 counterpart. G4s are stable structures; however, their geometrical parameters may be finely tuned not only by the presence of particular sequences of nucleotides but also by the salt content of the medium or by a small molecule that may act as a peculiar topology inducer. As far as the interest in G4s increases and our knowledge of these species deepens, researchers do not only verify the G4s binding by small molecules and the subsequent G4 stabilisation. The most innovative studies now aim to elucidate the mechanistic details of the interaction and the ability of a target species (drug) to bind only to a peculiar G4 geometry. In this focused review, we survey the advances in the studies of the binding of small molecules of medical interest to G4s, with particular attention to the ability of these species to bind differently (intercalation, lateral binding or sitting atop) to different G4 topologies (parallel, anti-parallel or hybrid structures). Some species, given the very high affinity with some peculiar G4 topology, can first bind to a less favourable geometry and then induce its conversion. This aspect is also considered.

Guanine Analogue-Based Assemblies: Construction and Luminescence Functions

As one of the natural nucleobases, guanine has attracted increasing interest in molecular self-assembly science because of its abundant interaction sites and high electron cloud density. Guanines, guanine derivatives, and guanine-rich DNA sequence are able to self-assemble into versatile aggregate structures by the means of hydrogen bonds and π-π, ion-dipole, solvophobic, and electrostatic interactions. Recent advances have shown that many guanine analogue-based (G-based) luminescent aggregates exhibit promising applications for fluorescent and chemiluminescent sensing and circularly polarized luminescence (CPL). This perspective summarizes the state-of-art strategies for constructing G-based assemblies and presents representative examples for luminescence functions. Finally, the inspirations are provided for exploiting unique G-based systems and luminescent G-based assemblies.

Feedback-controlled topological reconfiguration of molecular assemblies for programming supramolecular structures

In biology, nonequilibrium assembly is characterized by fuel-driven switching between associating and nonassociating states of biomolecules. This dynamic assembly model has been used routinely to describe the nonequilibrium processes in synthetic systems. Here, we present a G-quartet-based nonequilibrium system based on fuel-driven co-assembly of guanosine 5'-monophosphate disodium salt hydrate and urease. Addition of lanthanum(III) ions to the system caused macroscopic dynamic switching between precipitates and hydrogels. Interestingly, combined analyses of the nonequilibrium systems demonstrated that molecules could switch between two distinct associating states without undergoing a nonassociating state. This finding suggested a nonequilibrium assembly mechanism of topological reconfiguration of molecular assemblies. We detailed quantitatively the nonequilibrium assembly mechanism to precisely control the phase behaviors of the active materials; thus, we were able to use the materials for transient-gel-templated polymerization and transient circuit connection. This work presents a new nonequilibrium system with unusual phase behaviors, and the resultant active hydrogels hold promise in applications such as fluid confinements and transient electronics.

Understanding self-assembly at molecular level enables controlled design of DNA G-wires of different properties

A possible engineering of materials with diverse bio- and nano-applications relies on robust self-assembly of oligonucleotides. Bottom-up approach utilizing guanine-rich DNA oligonucleotides can lead to formation of G-wires, nanostructures consisting of continuous stacks of G-quartets. However, G-wire structure and self-assembly process remain poorly understood, although they are crucial for optimizing properties needed for specific applications. Herein, we use nuclear magnetic resonance to get insights at molecular level on how chosen short, guanine-rich oligonucleotides self-assemble into G-wires, whereas complementary methods are used for their characterization. Additionally, unravelling mechanistic details enable us to guide G-wire self-assembly in a controlled manner. MD simulations provide insight why loop residues with considerably different properties, i.e., hydrogen-bond affinity, stacking interactions, electronic effects and hydrophobicity extensively increase or decrease G-wire length. Our results provide fundamental understanding of G-wire self-assembly process useful for future design of nanomaterials with specific properties.

G-wire structures have potential applications in bio-nanotechnology, however, this is limited by a lack of understanding about the assembly process and structures formed. Here, the authors use nuclear magnetic resonance and molecular dynamic simulations to understand the guiding principles of G-wire assembly.

Affibody Modified G-quadruplex DNA Micelles Incorporating Polymeric 5-Fluorodeoxyuridine for Targeted Delivery of Curcumin to Enhance Synergetic Therapy of HER2 Positive Gastric Cancer

Combination chemotherapy is emerging as an important strategy for cancer treatment with decreased side effects. However, chemotherapeutic drugs with different solubility are not easy to realize co-delivery in traditional nanocarriers. Herein, an affibody modified G-quadruplex DNA micellar prodrug (affi-F/GQs) of hydrophilic 5-fluorodeoxyuridine (FUdR) by integrating polymeric FUdRs into DNA strands is developed for the first time. To achieve synergistic efficacy with hydrophobic drugs, curcumin (Cur) is co-loaded into affi-F/GQs micelles to prepare the dual drug-loaded DNA micelles (Cur@affi-F/GQs), in which affibody is employed as a targeting moiety to facilitate HER2 receptor-mediated uptake. Cur@affi-F/GQs have a small size of approximately 130 nm and exhibit excellent stability. The system co-delivers FUdR and Cur in a ratiometric manner, and the drug loading rates are 21.1% and 5.6%, respectively. Compared with the physical combination of FUdR and Cur, Cur@affi-F/GQs show higher cytotoxicity and greater synergistic effect on HER2 positive gastric cancer N87 cells. Surprisingly, Cur@affi-F/GQs significantly enhance the expression and activity of apoptosis-associated proteins in Bcl-2/Bax-caspase 8, 9-caspase 3 apoptotic pathway, which is the main factor in the death of tumor cells induced by FUdR. Overall, this nanoencapsulation is a promising candidate for the targeted co-delivery of drugs with significant differences in solubility.

Guanosine Borate Hydrogel and Self-Assembled Nanostructures Capable of Enantioselective Aldol Reaction in Water

A guanosine-based hydrogel formed by the self-assembly of guanosine and 4-((l-prolinamide)methyl)phenylboronic acid was constructed. The G quartets were selectively stabilized by K⁺ ions to form a self-supporting transparent hydrogel. These guanosine-derived assemblies were used to catalyze the aldol reaction in water without any additives, affording desirable conversion and enantioselectivity of the product. The controlled assays of small-molecule components indicated that the stable assemblies were the definite species that achieved high enantioselective catalysis. The current catalytic system can be readily recovered by simple extraction and still acquired good performance of the reaction after four cycles.

Discovering New G-Quadruplex DNA Catalysts in Enantioselective Sulfoxidation Reaction

The natural human telomeric G-quadruplex (G4) sequence d(GGGTTAGGGTTAGGGTTAGGG) HT21 was extensively utilized as a G4 DNA-based catalytic system for enantioselective reactions. Nine oligonucleotides (ODNs) based on this sequence and containing 8-bromo-2′-deoxyadenosine (A^Br), 8-oxo-2′-deoxyadenosine (A^oxo) or β-L-2′-deoxyadenosine (A^L) at different single loop positions were investigated to evaluate their performances as DNA catalysts in an enantioselective sulfoxidation reaction of thioanisole. The substitution of an adenosine in the loops of HT21 with these modified residues had a negligible impact on the G4 DNA structural features, thermal stability, and catalytic activity, since almost all investigated ODNs were able to form G-quadruplexes strictly resembling that of HT21 and catalyze a full conversion of the thioanisole substrate. More marked effects were obtained in chiral selectivity of G4 DNA metalloenzymes, considering that in most cases the DNA-modified catalysts induced lower enantioselectivities compared to the natural one. However, the HT21 derivative containing an A^L residue in the first loop sequence significantly proved to be capable of producing about 84% enantiomeric excess, the highest enantioselectivity for DNA-based oxidation reaction to date.

In Situ Electrical Monitoring of Methylated DNA Based on Its Conformational Change to G-Quadruplex Using a Solution-Gated Field-Effect Transistor

Methylated DNA is not only a diagnostic but also a prognostic biomarker for early-stage cancer. However, sodium bisulfite sequencing as a "gold standard" method for detection of methylation markers has some drawbacks such as its time-consuming and labor-intensive procedures. Therefore, simple and reliable methods are required to analyze DNA sequences with or without methylated residues. Herein, we propose a simple and direct method for detecting DNA methylation through its conformation transition to G-quadruplex using a solution-gated field-effect transistor (SG-FET) without using labeled materials. The BCL-2 gene, which is involved in the development of various human tumors, contains G-rich segments and undergoes a conformational change to G-quadruplex depending on the K⁺ concentration. Stacked G-quadruplex strands move close to the SG-FET sensor surface, resulting in large electrical signals based on intrinsic molecular charges. In addition, a dense hydrophilic polymer brush is grafted using surface-initiated atom transfer radical polymerization onto the SG-FET sensor surface to reduce electrical noise based on nonspecific adsorption of interfering species. In particular, control of the polymer brush thickness induces electrical signals based on DNA molecular charges in the diffusion layer, according to the Debye length limit. A platform based on the SG-FET sensor with a well-defined polymer brush is suitable for in situ monitoring of methylated DNA and realizes a point-of-care device with a high signal-to-noise ratio and without the requirement for additional processes such as bisulfite conversion and polymerase chain reaction.

Stimuli-Responsive and Reversible Nanoassemblies of G-Triplexes

G-triplex (G3) structures formed with three consecutive G-tracts have recently been identified as a new emerging guanine-rich DNA fold. There could likely be a wide range of biological functions for G3s as occurring for G-quadruplex (G4) structures formed with four consecutive G-tracts. However, in comparison to the many reports on G4 nanoassemblies that organize monomers together in a controllable manner, G3-favored nanoassemblies have yet to be explored. In this work, we found that a natural alkaloid of sanguinarine can serve as a dynamic ligand glue to reversibly switch the dimeric nanoassemblies of the thrombin binding aptamer G3 (TBA-G3). The glue planarity was considered to be a crucial factor for realizing this switching. More importantly, external stimuli including pH, sulfite, O₂ and H₂ O₂ can be employed as common regulators to easily modulate the glue's adhesivity for constructing and destructing the G3 nanoassemblies as a result of the ligand converting between isoforms. However, this assembly behavior does not occur with the counterpart TBA-G4. Our work demonstrates that higher-order G3 nanoassemblies can be reversibly operated by manipulating ligand adhesivity. This provides an alternative understanding of the unique behavior of guanine-rich sequences and focuses attention on the G3 fold since the nanoassembly event investigated herein might occur in living cells.

Kinetic control of chirality and circularly polarized luminescence in G-quartet materials

The formation of chirality of G-quartet materials has been of concern for a long time, however, the helix-handedness of G-quartet materials is still ambiguous, as well as the novel circularly polarized luminescence (CPL) properties. Here, we demonstrated that the handedness of G-quartet materials highly depends on their formation kinetics. By controlling the temperature or the initial concentration of reactants, we found that right-handed helical G-quartet nanostructures were synthesized in the slow process, while left-handed structures were synthesized in the fast process via orderly stacking. The phenomenon can be explained by the theory of kinetic trapping, in which a slow process leads to the thermodynamic equilibrium, while a fast process results in the kinetic trap state. Furthermore, the first kinetic trapping-controlled reversal CPL system was designed in G-quartet materials via chirality transfer, which has potential applications in CPL materials design and application.

Non-Canonical Helical Structure of Nucleic Acids Containing Base-Modified Nucleotides

Chemically modified nucleobases are thought to be important for therapeutic purposes as well as diagnosing genetic diseases and have been widely involved in research fields such as molecular biology and biochemical studies. Many artificially modified nucleobases, such as methyl, halogen, and aryl modifications of purines at the C8 position and pyrimidines at the C5 position, are widely studied for their biological functions. DNA containing these modified nucleobases can form non-canonical helical structures such as Z-DNA, G-quadruplex, i-motif, and triplex. This review summarizes the synthesis of chemically modified nucleotides: (i) methylation, bromination, and arylation of purine at the C8 position and (ii) methylation, bromination, and arylation of pyrimidine at the C5 position. Additionally, we introduce the non-canonical structures of nucleic acids containing these modifications.

Charge-Transfer Interactions Stabilize G-Quadruplex-Forming Thrombin Binding Aptamers and Can Improve Their Anticoagulant Activity

In the search for optimized thrombin binding aptamers (TBAs), we herein describe the synthesis of a library of TBA analogues obtained by end-functionalization with the electron-rich 1,5-dialkoxy naphthalene (DAN) and the electron-deficient 1,8,4,5-naphthalenetetra-carboxylic diimide (NDI) moieties. Indeed, when these G-rich oligonucleotides were folded into the peculiar TBA G-quadruplex (G4) structure, effective donor-acceptor charge transfer interactions between the DAN and NDI residues attached to the extremities of the sequence were induced, providing pseudo-cyclic structures. Alternatively, insertion of NDI groups at both extremities produced TBA analogues stabilized by π-π stacking interactions. All the doubly-modified TBAs were characterized by different biophysical techniques and compared with the analogues carrying only the DAN or NDI residue and unmodified TBA. These modified TBAs exhibited higher nuclease resistance, and their G4 structures were markedly stabilized, as evidenced by increased Tm values compared to TBA. These favorable properties were also associated with improved anticoagulant activity for one DAN/NDI-modified TBA, and for one NDI/NDI-modified TBA. Our results indicated that TBA pseudo-cyclic structuring by ad hoc designed end-functionalization represents an efficient approach to improve the aptamer features, while pre-organizing and stabilizing the G4 structure but allowing sufficient flexibility to the aptamer folding, which is necessary for optimal thrombin recognition.

Self-Assembly of Functionalized Lipophilic Guanosines into Cation-Free Stacked Guanine-Quartets

The hierarchical self-assembly of various lipophilic guanosines exposing either a phenyl or a ferrocenyl group in the C(8) position was investigated. In a solution, all the derivatives were found to self-assemble primarily into isolated guanine (G)-quartets. In spite of the apparent similar bulkiness of the two substituents, most of the derivatives form disordered structures in the solid state, whereas a specific 8-phenyl derivative self-assembles into an unprecedented, cation-free stacked G-quartet architecture.

Ruthenium(II) Complex-Based G-quadruplex DNA Selective Luminescent 'Light-up' Probe for RNase H Activity Detection

A bis-heteroleptic ruthenium(II) complex, 1[PF₆ ]₂ of benzothiazole amide substituted 2,2'-bipyridine ligand (bmbbipy) has been synthesized for the selective detection of G-quadruplex (GQ) DNA and luminescence-assay-based RNase H activity monitoring. Compound 1[PF₆ ]₂ exhibited aggregation-caused quenching (ACQ) in water. Aggregate formation was supported by DLS, UV-vis, and ¹ H NMR spectroscopy results, and the morphology of aggregated particles was witnessed by SEM and TEM. 1[PF₆ ]₂ acted as an efficient GQ DNA-selective luminescent light-up probe over single-stranded and double-stranded DNA. The competency of 1[PF₆ ]₂ for selective GQ structure detection was established by PL and CD spectroscopy. For 1[PF₆ ]₂ , the PL light-up is exclusively due to the rigidification of the benzothiazole amide side arm in the presence of GQ-DNA. The interaction between the probe and GQ-DNA was analyzed by molecular docking analysis. The GQ structure detection capability of 1[PF₆ ]₂ was further applied in the luminescent 'off-on' RNase H activity detection. The assay utilized an RNA:DNA hybrid, obtained from 22AG2-RNA and 22AG2-DNA sequences. RNase H solely hydrolyzed the RNA of the RNA:DNA duplex and released G-rich 22AG2-DNA, which was detected via the PL enhancement of 1[PF₆ ]₂ . The selectivity of RNase H activity detection over various other restriction enzymes was also demonstrated.

GGGCTA repeats can fold into hairpins poorly unfolded by replication protein A: a possible origin of the length-dependent instability of GGGCTA variant repeats in human telomeres

Human telomeres are composed of GGGTTA repeats and interspersed with variant repeats. The GGGCTA variant motif was identified in the proximal regions of human telomeres about 10 years ago and was shown to display a length-dependent instability. In parallel, a structural study showed that four GGGCTA repeats folded into a non-canonical G-quadruplex (G4) comprising a Watson-Crick GCGC tetrad. It was proposed that this non-canonical G4 might be an additional obstacle for telomere replication. In the present study, we demonstrate that longer GGGCTA arrays fold into G4 and into hairpins. We also demonstrate that replication protein A (RPA) efficiently binds to GGGCTA repeats structured into G4 but poorly binds to GGGCTA repeats structured into hairpins. Our results (along with results obtained with a more stable variant motif) suggest that GGGCTA hairpins are at the origin of GGGCTA length-dependent instability. They also suggest, as working hypothesis, that failure of efficient binding of RPA to GGGCTA structured into hairpins might be involved in the mechanism of GGGCTA array instability. On the basis of our present and past studies about telomeric G4 and their interaction with RPA, we propose an original point of view about telomeric G4 and the evolution of telomeric motifs.

Folding Dynamics of DNA G-Quadruplexes Probed by Millisecond Temperature Jump Circular Dichroism

G-quadruplexes play important roles in cellular regulatory functions, but despite significant experimental and theoretical efforts, their folding mechanisms remain poorly understood. In this context, we developed a T-jump experiment to access the thermal denaturation and renaturation dynamics of short intramolecular G-quadruplexes in vitro, on the time scale of a few hundred milliseconds. With this new setup, we compared the thermal denaturation and renaturation kinetics of three antiparallel topologies made of the human telomeric sequences d[(5'-GGG(TTAGGG)₃-3']/Na⁺ and d[5'-AGGG(TTAGGG)₃-3']/Na⁺ and the thrombin-binding aptamer sequence d[5'-GGTTGGTGTGGTTGG-3']/K⁺, with those of the parallel topology made of the human CEB25 minisatellite d[5'-AAGGGTGGGTGTAAGTGTGGGTGGGT-3']/Na⁺. In all cases, exponential kinetics of the order of several hundred milliseconds were observed. Measurements performed for different initial temperatures revealed distinct denaturation and renaturation dynamics, ruling out a simple two-state mechanism. The parallel topology, in which all guanines adopt an anti conformation, displays much slower dynamics than antiparallel topologies associated with very low activation barriers. This behavior can be explained by the constrained conformational space due to the presence of the single-base propeller loops that likely hinders the movement of the coiled DNA strand and reduces the contribution of the entropy during the renaturation process at high temperatures.

Spectroscopic and In Silico Studies on the Interaction of Substituted Pyrazolo[1,2-a]benzo[1,2,3,4]tetrazine-3-one Derivatives with c-Myc G4-DNA

Herein we describe a combined experimental and in silico study of the interaction of a series of pyrazolo[1,2-a]benzo[1,2,3,4]tetrazin-3-one derivatives (PBTs) with parallel G-quadruplex (GQ) DNA aimed at correlating their previously reported anticancer activities and the stabilizing effects observed by us on c-myc oncogene promoter GQ structure. Circular dichroism (CD) melting experiments were performed to characterize the effect of the studied PBTs on the GQ thermal stability. CD measurements indicate that two out of the eight compounds under investigation induced a slight stabilizing effect (2-4 °C) on GQ depending on the nature and position of the substituents. Molecular docking results allowed us to verify the modes of interaction of the ligands with the GQ and estimate the binding affinities. The highest binding affinity was observed for ligands with the experimental melting temperatures (Tms). However, both stabilizing and destabilizing ligands showed similar scores, whilst Molecular Dynamics (MD) simulations, performed across a wide range of temperatures on the GQ in water solution, either unliganded or complexed with two model PBT ligands with the opposite effect on the Tms, consistently confirmed their stabilizing or destabilizing ability ascertained by CD. Clues about a relation between the reported anticancer activity of some PBTs and their ability to stabilize the GQ structure of c-myc emerged from our study. Furthermore, Molecular Dynamics simulations at high temperatures are herein proposed for the first time as a means to verify the stabilizing or destabilizing effect of ligands on the GQ, also disclosing predictive potential in GQ-targeting drug discovery.

Characterization of In Vitro G-Quadruplex Formation of Imetelstat Telomerase Inhibitor

Imetelstat (GRN163L) is a potent and specific telomerase inhibitor currently in clinical development for the treatment of hematological malignancies such as myelofibrosis and myelodysplastic syndrome. It is a 13-mer N3'-P5' thio-phosphoramidate oligonucleotide covalently functionalized at the 5'-end with a palmitoyl lipid moiety through an aminoglycerol linker. As a competitive inhibitor of human telomerase, imetelstat directly binds to the telomerase RNA component sequence (hTR) in the catalytic site of the enzyme and acts as a direct competitor of human telomere binding. Administration of imetelstat causes progressive shortening of the telomeres, thereby inhibiting malignant cells' proliferation. We report here the ability of imetelstat to form stable, parallel, intermolecular G-quadruplex structures in vitro. The impact of the ionic environment on the formation and stability of imetelstat higher-order structure was investigated through circular dichroism spectroscopy, thermal denaturation analysis, and size-exclusion chromatography. We demonstrated that different structural elements, such as the 5'-palmitoyl linker and the thio-phosphoramidate backbone, critically contribute to G-quadruplex stability. Experiments further showed that G-quadruplex formation does not hamper binding to the hTR oligonucleotide sequence in vitro.

Divalent Cation Dependence Enhances Dopamine Aptamer Biosensing

Oligonucleotide receptors (aptamers), which change conformation upon target recognition, enable electronic biosensing under high ionic-strength conditions when coupled to field-effect transistors (FETs). Because highly negatively charged aptamer backbones are influenced by ion content and concentration, biosensor performance and target sensitivities were evaluated under application conditions. For a recently identified dopamine aptamer, physiological concentrations of Mg²⁺ and Ca²⁺ in artificial cerebrospinal fluid produced marked potentiation of dopamine FET-sensor responses. By comparison, divalent cation-associated signal amplification was not observed for FET sensors functionalized with a recently identified serotonin aptamer or a previously reported dopamine aptamer. Circular dichroism spectroscopy revealed Mg²⁺- and Ca²⁺-induced changes in target-associated secondary structure for the new dopamine aptamer, but not the serotonin aptamer nor the old dopamine aptamer. Thioflavin T displacement corroborated the Mg²⁺ dependence of the new dopamine aptamer for target detection. These findings imply allosteric binding interactions between divalent cations and dopamine for the new dopamine aptamer. Developing and testing sensors in ionic environments that reflect intended applications are best practices for identifying aptamer candidates with favorable attributes and elucidating sensing mechanisms.

How to untie G-quadruplex knots and why?

For over two decades, the prime objective of the chemical biology community studying G-quadruplexes (G4s) has been to use chemicals to interact with and stabilize G4s in cells to obtain mechanistic interpretations. This strategy has been undoubtedly successful, as demonstrated by recent advances. However, these insights have also led to a fundamental rethinking of G4-targeting strategies: due to the prevalence of G4s in the human genome, transcriptome, and ncRNAome (collectively referred to as the G4ome), and their involvement in human diseases, should we continue developing G4-stabilizing ligands or should we invest in designing molecular tools to unfold G4s? Here, we first focus on how, when, and where G4s fold in cells; then, we describe the enzymatic systems that have evolved to counteract G4 folding and how they have been used as tools to manipulate G4s in cells; finally, we present strategies currently being implemented to devise new molecular G4 unwinding agents.

Novel monomolecular derivatives of the anti-HIV-1 G-quadruplex-forming Hotoda's aptamer containing inversion of polarity sites

Here we report on the design, preparation and investigation of four analogues of the anti-HIV G-quadruplex-forming Hotoda's aptamer, based on an unprecedented linear topology. In these derivatives, four TGGGAGT tracts have been joined together by exploiting 3'-3' and 5'-5' inversion of polarity sites formed by canonical phosphodiester bonds or a glycerol-based linker. Circular dichroism data suggest that all oligodeoxynucleotides fold in monomolecular G-quadruplex structures characterized by a parallel strand orientation and three side loops connecting 3'- or 5'-ends. The derivative bearing two lipophilic groups, namely HT353LGly, inhibited virus entry into the host cell, with anti-HIV-1 activity in the low nanomolar range; the other derivatives, albeit sharing the same base sequence and similar topology, were inactive. These results highlight that monomolecular Hotoda's aptamers with inversion of polarity sites represent a successful alternative strategy that merges the easiness of synthesis with the maintenance of remarkable activity. They also indicate that two lipophilic groups are necessary and sufficient for biological activity. Our data will inspire the design of further simplified derivatives with improved biophysical and antiviral properties.

The effect of isomerism and other structural variations on the G-quadruplex DNA-binding properties of some nickel Schiff base complexes

A series of novel isomeric nickel Schiff base complexes, as well as nickel complexes of related ligands having asymmetric structures have been prepared and characterised using microanalysis, 1H and 13C NMR spectroscopy and ESI-MS. The Schiff base ligands were prepared by condensation reactions involving ethylenediamine and different derivatives of benzophenone. The solid-state structures of eight of the complexes were also determined and revealed that each possessed a regular square planar coordination geometry around the metal ion. Many of the new complexes featured at least one, and in many instances two, protonatable pendant groups that enhance aqueous solubility. This enabled the DNA binding properties of the latter complexes to be explored using a variety of instrumental approaches, including ESI-MS, circular dichroism (CD) spectroscopy, FRET melting assays and FID assays, as well as molecular docking studies. The results of experiments performed using ESI-MS suggested that none of the nickel complexes exhibit a high affinity towards either a double stranded DNA (dsDNA) molecule D2, or the parallel unimolecular quadruplex DNA (qDNA) molecule Q1. In contrast, complexes (8) and (12) both gave spectra which reflected a significant level of binding to the parallel tetramolecular qDNA Q4. The results of binding experiments performed using CD spectroscopy suggested that (12) exhibits a significant level of affinity towards most types of DNA, while (4) shows a preference for interacting with parallel, unimolecular qDNA molecules. Complex (4) produced the lowest values of DC50 in FID assays performed using parallel Q1 or Q4, confirming its affinity for these qDNA molecules. The results of FRET melting experiments provided further evidence that (12), along with (8), can interact extensively with anti-parallel unimolecular qDNA. Experiments which monitored the effect of the nickel complexes on the melting temperature of D2 showed that none had a stabilising effect on this dsDNA molecule.

A guanosine-based 2-formylphenylborate ester hydrogel with high selectivity to K+ ions

Guanosine-based supramolecular hydrogels are particularly of interest for biomaterial and biomedical purposes, as they are generally biocompatible and stimuli-responsive. We found a strong and long-life transparent hydrogel made by mixing guanosine (G) with 1 equiv. of 2-formylbenzeneboronic acid (2FPB) and KOH. Alkali cations can assist the stacking of individual G-quartet to give extended nanowires, but only K⁺ ion induces the formation of a stable and self-supporting network hydrogel for a couple of months. Data from variable temperature NMR indicated that guanosine 2-formylbenzeneborate ester and G are the key components of the self-assembly. Further, G-2FPB-K⁺ hydrogel solution can induce berberine (BBR) fluorescence, showing high selectivity to K⁺ ion and anti-ion interference capability. A good linear relationship between fluorescent intensity and K⁺ concentration allowed us to directly detect K⁺ levels in human blood serum.

A new self-assembling system prepared from guanosine and 2-formylbenzeneboronic acid showed a high selectivity to potassium ions and has a fluorescent enhancement effect on berberine, which can be used for serum potassium detection.

Right-/left-handed helical G-quartet nanostructures with full-color and energy transfer circularly polarized luminescence

Right (R)- and left (L)-handed helical G-quartet nanostructures were synthesized for the first time simultaneously via the self-assembly of 5'-guanosine monophosphate (GMP), the helical handedness of which is well regulated by metal ions. These g-nanostructures were further applied as circularly polarized luminescence (CPL) templates to realize full-color R-/L-CPL and Förster resonance energy transfer CPL. The glum value reached 10-2, indicating their excellent template function for CPL materials design and application.