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2,5-Furandicarboxylic acid (FDCA) is one of the top-12 value-added chemicals from sugar. Besides the wide application in chemical industry, here we found that solid FDCA polymerized to form an atomic-scale ordered sp

DNA small molecular probe study was considered as a promising approach to achieve DNA related disease diagnosis. Most related reports were performed under specific salinity. Herein, 4-imino-3-(pyridin-2-yl)-4H-quinolizine-1-carbonitrile (IPQC) was generated via a facile procedure with high yield (85%). It is found that IPQC could act as a universal probe for most tested ssDNA, dsDNA and G4 DNA in low [K+] concentration (less than 20 mM). However, IPQC showed highly selective G4 DNA binding via UV-vis and fluorescence response in increasing [K+] (e.g., 150 mM) conditions. The ion atmosphere effects are instructive for DNA probe exploration. This provides guidance for the design, selection and optimization of the probes for target DNA sensing.

Mitochondria autophagy, also known as mitophagy, is a process in which mitochondria are wrapped by autophagosomes and fused with lysosomes for degradation. This process is essential for mitochondrial quality control. Here, we developed a hybrid aggregate FRET probe through mixed assembly of two cyanine dyes FMOTY and AMTC. In live cells, FMOTY and AMTC exist independently in lysosomes and mitochondria and will not produce interfering FRET background signals. The FRET signal is only generated when mitochondria is transported to lysosomes during mitophagy. This allows the hybridized aggregate to be used as a highly specific probe for monitoring mitophagy.

DNA small molecular probe study was considered as a promising approach to achieve DNA related disease diagnosis. Most related reports were performed under specific salinity. Herein, 4-imino-3-(pyridin-2-yl)-4

Background G-quadruplex has been viewed as a promising therapeutic target in oncology due to its potentially important roles in physiological and pathological processes. Emerging evidence suggests that the biological functions of G-quadruplexes are closely related to the binding of some proteins. Insulin-like growth factor type I (IGF-1), as a significant modulator of cell growth and development, may serve as a quadruplex-binding protein. Methods The binding affinity and selectivity of IGF-1 to different DNA motifs in solution were measured by using fluorescence spectroscopy, Surface Plasmon Resonance (SPR), and force-induced remnant magnetization (FIRM). The effects of IGF-1 on the formation and stability of G-quadruplex structures were evaluated by circular dichroism (CD) and melting fluorescence resonance energy transfer (FRET) spectroscopy. The influence of quadruplex-specific ligands on the binding of G-quadruplexes with IGF-1 was determined by FIRM. Results IGF-1 shows a binding specificity for G-quadruplex structures, especially the G-quadruplex structure with a parallel topology. The quadruplex-specific ligands TMPyP4 and PDS (Pyridostatin) can inhibit the interaction between G-quadruplexes and proteins. Conclusions IGF-1 is demonstrated to selectively bind with G-quadruplex structures. The use of quadruplex-interactive ligands could modulate the binding of IGF-1 to G-quadruplexes. General significance This study provides us with a new perspective to understand the possible physiological relationship between IGF-1 and G-quadruplexes and also conveys a strategy to regulate the interaction between G-quadruplex DNA and proteins.

Chirality at a supramolecular level is currently attracting great attention attributed to rapid developments in supramolecular chemistry. Herein, we report a new type of chiral self-assembly based on the cyanine dye MTC. The chiral H-aggregates of MTC could form spontaneously from achiral J-aggregates, and could return back to achiral J-aggregates in high concentration on increasing the solution temperature.

Monitoring autophagy can provide valuable insights into understanding human pathological mechanisms, developing novel drugs, and exploring autophagy control approaches. Here, we proposed a new strategy to specifically monitor autophagy by lighting up the G-quadruplex structures entering autolysosomes. Based on this strategy, we designed a small-molecule fluorescent probe for autophagy imaging. This work not only opens up a new way for developing autophagy probes, but also provides an effective tool for autophagy research.

G-quadruplex DNA has been viewed as a prospective anti-cancer target owing to its potential biological relevance. Real-time monitoring of DNA G-quadruplex structures in living cells can provide valuable insights into the relationship between G-quadruplex formation and its cellular consequences. However, the probes capable of detecting DNA G-quadruplexes in living cells are still very limited. Herein, we reported a new fluorescent probe, IMT, for real-time visualization of DNA G-quadruplex structures in living cells. Using IMT as a fluorescent indicator, the quantity changes of DNA G-quadruplex at different points in time during continuous cellular progression responding to Aphidicolin and Hydroxyurea treatment have been directly visualized. Our data demonstrate that IMT will be a valuable tool for exploring DNA G-quadruplexes in live cells. Further application of IMT in fluorescence imaging may reveal more information on the roles of DNA G-quadruplexes in biological systems.

G-quadruplex has attracted considerable attention due to their prevalent distribution in functional genomic regions and transcripts, which can importantly influence biological processes such as regulation of telomere maintenance, gene transcription and gene translation. Artificial receptor study has been developed for accurate identification of G-quadruplex from DNA species, since it is important for the G-quadruplex related basic research, clinical diagnosis, and therapy. Herein, fluorescent dye ThT-E, a derivative of the known fluorescence probe Thioflavin T (ThT), was designed and synthesized to effectively differentiate various G-quadruplex structures from other nucleic acid forms. Compared with methyl groups in ThT, three ethyl groups were introduced to ThT-E, which leads to strengthened affinity, selectivity and little inducing effect on the G-quadruplex formation. More importantly, ThT-E could be served as a visual tool to directly differentiate G-quadruplex solution even with naked eyes under illumination of ultraviolet light. Thus, this probe reported herein may hold great promise for high-throughput assay to screen G-quadruplex, which may widely apply to G-quadruplex-based potential diagnosis and therapy.

G-quadruplex has been an emerging target for drug design due to its physiologically important roles in oncology. A number of quadruplex-interactive ligands have been developed by synthetic and medicinal chemists over the past decades. However, the great challenge still remains that the method for detecting the specific targeting of these ligands to the G-quadruplex structures in cells is still lacking. Herein, a detection system for directly identifying the specific targeting of a ligand to DNA G-quadruplexes in cells was constructed by using a small-molecular fluorescent probe (IMT) as a fluorescent indicator. Four typical ligands have been successfully evaluated, demonstrating the promising application of this detection system in the screening and evaluation of quadruplex-specific therapeutic agents., Graphical abstract Image 1, Highlights • An effective system for assessing the targeting of G-quadruplex ligands in living cells is reported. • The targeting of four typical ligands to G-quadruplexes in live cells was successfully determined. • This detection system shows promising applications in the screening and evaluation of quadruplex-targeted drugs.

C-myc promoter G-quadruplex is a very important target for developing anti-cancer drugs. However, highly selective recognition of DNA c-myc G-quadruplex with parallel configuration is also a very challenging problem. Here, we showed a new type of N-containing alkaloid, 3,8a-disubstituted indolizinone, which adopted a distorted configuration. 6-Methyl-3-(naphthalen-2-yl)-8a-(4-methylpyridin-2-yl)-indolizinone could selectively recognize DNA c-myc G-quadruplex leading to an obvious fluorescence enhancement by 11-fold, and meanwhile the G-quadruplex can be stabilized up to 90 °C. Further, it could down-regulate the transcription of oncogene c-myc in both human non-small cell line (A549) and human laryngeal epithelial cell line (Hep-2).

There has been a big challenge in developing the Na(+) sensor that can be practically used in the physiological system with the interference of large amounts of K(+). In this research, a novel Na(+) sensor has been designed based on the G-quadruplex-conformation related DNAzyme activity. The sensor exhibits high selectivity and sensitivity with the detection limit of 0.6 μM, which enables the sensor to be practically used in determination of the Na(+) level in serum. The research not only provides a simple Na(+) sensor but also opens a new way for developing the detection technology of Na(+).

Multiple cycle regulation of the supramolecular chirality of a cyanine dye has been successfully achieved by using DNA G-quadruplexes as templates, which is easily controllable by repeated addition of Ag(+) and cysteine (Cys). This work provides an easy and controllable strategy for the chiral regulation of supramolecules.

It is found that G-quadruplexes have important functions in biological systems, such as gene expression. Molecules which can stabilize the G-quadruplex structure may have potential application in regulating the expression of gene. A series of methylazacalix[n]pyridine (n = 4, 6, 7, 8, 9) has been tested to stabilize the intermolecular human telomeric G-quadruplex (T12 and H12), intramolecular TBA, c-kit and bcl-2 G-quadruplex by CD denaturation experiments. The results showed that only methylazacalix[6] pyridine (MACP6) can stabilize the intermolecular G-quadruplex formed from the 12 bp human telomere. Further studies evidenced that the shape-complementary binding mode was what contributed to the interaction between MACP6 and T12 G-quadruplex. (C) 2015 Elsevier Ltd. All rights reserved.

The cyanine dyes are among the oldest classes of synthetic compounds but continue to find applications in a variety of fields. Compared to other organic molecules, diverse and controlled aggregate property is one most canonic feature of the cyanine dyes. With a primary focus on our own work, here we chose 3,3'-di(3-sulfopropyl)-4,5,4',5'-dibenzo-9-methyl-thiacarbo-cyanine triethylammonium salt as one model to discuss its controllable aggregates and its applications served as a chemosensor. Its H- and J-aggregates could be conversed mutually by the regulation of metal-salts or temperature or small peptides, presenting varied characteristic absorption spectra. And its J- or H-aggregates could be destroyed and converted to monomeric states, respectively by human serum albumin or G-quadruplex DNA. Furthermore, it was sensitive to the subtle conformer of G-quadruplex, and thus applied in detecting the Na+/K+ ratio or Pb2+ concentration in the solution samples as a chemosensor. (C) 2015 Elsevier Ltd. All rights reserved.

G-quadruplex as a therapeutic target to develop novel anti-cancer agents has attracted a growing interest. Among all the ligands of G-quadruplexes, pyridostatin derivatives play a very important role. Here, we first reported the recognition of the fundamental skeleton pyridostatin I, which was simply synthesized. Compared to pyridostatin II comprising terminal amino groups, pyridostatin I selectively stabilized intramolecular anti-parallel telomeric G-quadruplex by raising the melting temperature about 20 degrees C at 295 rim of H22, while pyridostatin II preferred to stabilize intermolecular parallel telomeric G-quadruplex by raising the melting temperature about 25 degrees C at 265 nm of H7, maybe due to the suited size measurements between G-quadruplex hosts and pyridostatin guests. MTT assays indicated that pyridostatin II had better cytotoxic effects against HCT-8 and A549 cell lines obviously, indicating positively charged side chains may be required for improving the water solubility and cellular uptake of the apolar central skeleton. (C) 2015 Published by Elsevier Ltd.

G-quadruplexes (G4s) play important roles in biological systems, such as telomere maintenance, replication, and transcription. Based on the DNA sequence, loop geometry, and the local environments, G4s can be classified into different conformations. It is important to detect different types of G4s to monitor the diseases related with G4s. Most ligands bind to G4s based on end-stacking modes, while rare ligands bind to G4s through groove binding modes. We have found that a cyanine dye DMSB interacts with parallel G4 by end-stacking and groove simultaneous binding mode. In this article, we found that DMSB could simply discriminate parallel G4s from other DNA motifs by using UV-vis spectrum. These results give some clues to develop high specificity G4 probes. (C) 2015 Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences. Published by Elsevier B.V. All rights reserved.

A series of dimeric cyanine dyes were designed to study their recognition for parallel c-myc G-quadruplex as well as their spectral features in solution. Dimeric cyanine dyes having different length linkers show their recognition for c-myc over duplex DNAs following the order: TC-P4 > TC-P5 > TC-P6 > TC-P3 > TC-P7 [the numeral is the number of repeat units (oligo-oxyethylene) in the linker]. This behaviour might result from their binding with G-quadruplex: the two chromophores of dimers stack on both ends of G-quadruplexes while the linker between two chromophores of dimers binds to the loops and grooves cooperatively. Further, these dyes presented an ability to differentiate the cervical cancer cell (Hela) from the normal cervical epithelial cell (CRL2614). These dyes have promising potential to be sensors to diagnose the G-quadruplex related diseases.

Background Direct detection of G-quadruplexes in human cells has become an important issue due to the vital role of G-quadruplex related to biological functions. Despite several probes have been developed for detection of the G-quadruplexes in cytoplasm or whole cells, the probe being used to monitor the nucleolar G-quadruplexes is still lacking. Methods Formation of the nucleolar G-quadruplex structures was confirmed by using circular dichroism (CD) spectroscopy. The binding affinity and selectivity of Thioflavin T (ThT) towards various DNA/RNA motifs in solution and gel system were measured by using fluorescence spectroscopy and polyacrylamide gel electrophoresis (PAGE), respectively. G-quadruplex imaging in live cells was directly captured by using confocal laser scanning microscopy (CLSM). Results Formation of the rDNA and rRNA G-quadruplex structures is demonstrated in vitro. ThT is found to show much higher affinity and selectivity towards these G-quadruplex structures versus other nucleic acid motifs either in solution or in gel system. The nucleolar G-quadruplexes in living cells are visualized by using ThT as a fluorescent probe. G-quadruplex-ligand treatments in live cells lead to sharp decrease of ThT signal. Conclusions The natural existence of the G-quadruplexes structure in the nucleoli of living cells is directly visualized by using ThT as an indicator. General significance The research provides substantive evidence for formation of the rRNA G-quadruplex structures, and also offers an effective probe for direct visualization of the nucleolar G-quadruplexes in living cells.

Background A new G-quadruplex structure located in the B-cell CLL/lymphoma 2 (Bcl-2) P1 promoter and its physiological function related to Bcl-2 transcription have been studied to find a potential anticancer therapeutic target. Methods Absorption, polyacrylamide gel electrophoresis, fluorescence, circular dichroism, and nuclear magnetic resonance spectra have been employed to determine G-quadruplex structure and the interaction between G-quadruplex and phenanthrolin-dicarboxylate. Real time polymerase chain reaction and luciferase assay were done to assess the physiological function of the G-quadruplex structure. Results The UV-melting and polyacrylamide gel electrophoresis studies show that the p32 DNA sequence forms an intramolecular G-quadruplex structure. Circular dichroism and nuclear magnetic resonance spectra indicate that the G-quadruplex is a hybrid-type structure with four G-tetrads. Fluorescence spectra show that a phenanthroline derivative has a higher binding affinity for p32 G-quadruplex than duplex. Further circular dichroism and nuclear magnetic resonance studies indicate that the phenanthroline derivative can regulate p32 G-quadruplex conformation. Real time polymerase chain reaction and luciferase assays show that the phenanthroline derivative has down-modulated Bcl-2 transcription activity in a concentration-dependent manner. However, no such effect was observed when p32 G-quadruplex was denatured through base mutation. Conclusion The newly identified G-quadruplex located in the P1 promoter of Bcl-2 oncogene is intimately related with Bcl-2 transcription activity, which may be a promising anticancer therapeutic target. General significance The newly identified G-quadruplex in the Bcl-2 P1 promoter may be a novel anticancer therapeutic target.

A colorimetric and fluorometric dual-modal supramolecular chemosensor has been fabricated by using the H- and J-aggregates of a cyanine dye, which has been successfully applied to detect human serum albumin (HSA) in urine with high specificity.

A simple technology to construct diverse DNA logic gates (OR and INHIBIT) has been designed utilizing a H(+) and/or Ag(+) induced i-motif structure. The logic gates are easily controlled and also show a real time response towards inputs. The research provides a new insight for designing DNA logic gates using an i-motif DNA structure.

G-quadruplexes attract more and more attention in recent years. Numerous small molecules which can induce or stabilize the formation of G-quadruplexes have been investigated on the purpose of anticancer drug development. As a motif existed in physiological condition, flanking sequences are an important part of G-quadruplexes but the study on the impact of flanking sequences on (G-quadruplex)-ligand binding is rarely reported. In this paper, the effects of flanking sequences on binding affinity between a series of unimolecular parallel-stranded G-quadruplex sequences derived from c-myc oncogene promoter (termed as c-myc G-quadruplexes) and their ligands are discussed in detail. The results showed that the flanking sequences on c-myc G-quadruplexes play key roles in (G-quadruplex)-ligand interaction. When a c-myc G-quadruplex is bound to its ligands, the flanking sequences might form a binding cavity above the terminal G-quartet, which could provide a suitable site for ligands to dock in. Moreover, the bases on flanking sequences could interact with ligand through π-π stacking, and finally form a sandwich-stacking mode (terminal G-quartet, ligand and bases on the flanking sequence). This mode could stabilize the (G-quadruplex)-ligand complex effectively and enhance the binding affinity dramatically. However, flanking sequences are also found to exhibit steric hindrance effect which could impede the (G-quadruplex)-ligand binding.

Burkitt lymphoma (BL) is a rare and highly aggressive type of non-Hodgkin lymphoma. The mortality rate of BL patients is very high due to the rapid growth rate and frequent systemic spread of the disease. A better understanding of the pathogenesis, more sensitive diagnostic tools and effective treatment methods for BL are essential. Metabolomics, an important aspect of systems biology, allows the comprehensive analysis of global, dynamic and endogenous biological metabolites based on their nuclear magnetic resonance (NMR) and mass spectrometry (MS). It has already been used to investigate the pathogenesis and discover new biomarkers for disease diagnosis and prognosis. In this study, we analyzed differences of serum metabolites in BL mice and normal mice by NMR-based metabolomics. We found that metabolites associated with energy metabolism, amino acid metabolism, fatty acid metabolism and choline phospholipid metabolism were altered in BL mice. The diagnostic potential of the metabolite differences was investigated in this study. Glutamate, glycerol and choline had a high diagnostic accuracy; in contrast, isoleucine, leucine, pyruvate, lysine, α-ketoglutarate, betaine, glycine, creatine, serine, lactate, tyrosine, phenylalanine, histidine and formate enabled the accurate differentiation of BL mice from normal mice. The discovery of abnormal metabolism and relevant differential metabolites may provide useful clues for developing novel, noninvasive approaches for the diagnosis and prognosis of BL based on these potential biomarkers.

G-quadruplexes have attracted growing attention as a potential cancer-associated target for both treatment and detection in recent years. For detection purpose, high specificity is one of the most important factors to be considered in G-quadruplex probe design. It is well known that end stacking and groove binding are two dominated quadruplex-ligand binding modes, and currently most reported G-quadruplex probes are designed based on the former, which has been proven to show good selectivity between quadruplexes and non-quadruplexes. Because groove of G-quadruplex also has some unique chemical properties, it could be inferred that probes that can interact with both the groove and G-tetrad site of certain G-quadruplexes simultaneously might possess higher specificity in aspects of discriminating different quadruplexes. In this article, we report a cyanine dye as a potential novel probe scaffold that could occupy both the 5′-end external G-tetrad and the corresponding groove of the G-quadruplex simultaneously. By using various spectrum and nuclear magnetic resonance techniques, we give a detailed binding characterization for this dual-site simultaneous binding mode. A preliminary result suggests that this mode might provide highly specific recognition to a parallel-stranded G-quadruplex. These findings and the structural elucidation might give some clues in aspects of developing highly specific G-quadruplex probes.

The G-quadruplex ligands database (G4LDB, http://www.g4ldb.org) provides a unique collection of reported G-quadruplex ligands to streamline ligand/drug discovery targeting G-quadruplexes. G-quadruplexes are guanine-rich nucleic acid sequences in human telomeres and gene promoter regions. There is a growing recognition for their profound roles in a wide spectrum of diseases, such as cancer, diabetes and cardiovascular disease. Ligands that affect the structure and activity of G-quadruplexes can shed light on the search for G-quadruplex-targeting drugs. Therefore, we built the G4LDB to (i) compile a data set covering various physical properties and 3D structure of G-quadruplex ligands; (ii) provide Web-based tools for G-quadruplex ligand design; and (iii) to facilitate the discovery of novel therapeutic and diagnostic agents targeting G-quadruplexes. G4LDB currently contains >800 G-quadruplex ligands with ∼4000 activity records, which, to our knowledge, is the most extensive collection of its kind. It offers a user friendly interface that can meet a variety of data inquiries from researchers. For example, ligands can be searched for by name, molecular properties, structures, ligand activities and so on. Building on the reported data, the database also provides an online ligand design module that can predict ligand binding affinity in real time.

Calixaromatics have attracted much attention on molecular recognition owing to their flexible conformations, cavity structures, versatile recognition properties, and functions. However, conformational control of calixaromatics is still a challenging topic in the field of calixaromatics. Therefore, we explore the possibility to control the chirality of achiral calixaromatics, methylazacalix[6]pyridine (abbreviated as MACP6), by templating of DNA. We have found that MACP6 with opposite chirality can be achieved by controlling the secondary structure of bcl-2 2345 DNA. Furthermore, MACP6 with different chirality has been used to recognize fullerene derivatives in aqueous solution. Our results have provided a possible approach to construct chiral calixaromatics.

A novel trend in G-quadruplex ligand design is to build a binder that is able to not only discriminate G-quadruplex from duplex-DNA, but also among various G-quadruplex structures. Methylazacalix[6]pyridine (MACP6), a new type of azacalixarene with flexible conformation, exhibits induced circular dichroism signals when interacted with most of G-quadruplexes. The intensities of the induced signals are strongly dependent on the topology of G-quadruplexes. Further evidence has shown that these signals can be ascribed to the preferred binding of MACP6 to the loops of G-quadruplexes, which rely on the nature of nucleotides in the loops.

Single-stranded telomeric DNA tends to form a four-base-paired planar structure termed G-quadruplex. Although kinds of G-quadruplex structures in vitro have been documented in the presence of potassium or sodium, recognition of these DNA motifs (both in vitro and in vivo) is still an important issue in understanding the biological function of the G-quadruplex structures in telomeres as well as developing anticancer agents. Herein we address this important question through the distinctive properties of a supramolecular system of cyanine dye 3,3′-di(3-sulfopropyl)-4,5,4′,5′-dibenzo-9-methyl-thiacarbocyanine triethylammonium salt (MTC) upon binding to different DNA motifs. Interaction of MTC with hybrid/mixed G-quadruplex results in a set of unique spectrophotometric signatures which are completely different from those arising from binding to other DNA motifs. Furthermore, such feature could be extended to map the locations of DNAs on interface. Linear duplex and mixed G-quadruplex in human telomeres assembled on Au film and stained by MTC were directly recognized by confocal laser scanning microscopy (CLSM). All results suggested that MTC supramolecular system may be a good probe of specific G-quadruplex structure.

The supramolecular assembly of a novel cyanine dye, 3,3'-di(3-sulfopropyl)-4,5,4',5'-dibenzo-9-ethyl-thiacarbocyanine triethylammonium salt (ETC) was designed to verify specific intramolecular G-quadruplexes from duplex and single-strand DNAs. Spectral results have shown that ETC presented two major distinct signatures with specific intramolecular G-quadruplexes in vitro: (i) dramatic changes in the absorption spectra (including disappearance of absorption peak around 660 nm and appearance of independent new peak around 584 nm); (ii) approximately 70 times enhancement of fluorescence signal at 600 nm. Furthermore, based on (1)H-nuclear magnetic resonance and circular dichroism results, the preferring binding of ETC to specific intramolecular G-quadruplexes probably result from end-stacking, and the loop structure nearby also plays an important role.

Human DNA sequences consisting of tandem guanine (G) nucleotides can fold into a four-stranded structure named G-quadruplex via Hoogsteen hydrogen bonding. As the sequences forming G-quadruplex exist in essential regions of eukaryotic chromosomes and are involved in many important biological processes, the study of their biological functions has currently become a hotspot. Compounds selectively binding and stabilizing G-quadruplex structures have the potential to inhibit telomerase activity or alter oncogene expression levels and thus may act as antitumor agents. Most of reported G-quadruplex ligands generally have planar structures which stabilize G-quadruplex by pi-pi stacking. However, based on a pharmacophore-based virtual screening two non-planar G-quadruplex ligands were found. These two ligands exhibit good capability for G-quadruplex stabilization and prefer binding to paralleled G-quadruplex rather than to duplex DNA. The binding of these ligands to G-quadruplex may result from groove binding at a 2:1 stoichiometry. These results have shown that planar structures are not essential for G-quadruplex stabilizers, which may represent a new class of G-quadruplex-targeted agents as potential antitumor drugs.

Nucleic acid based molecular device is a developing research field which attracts great interests in material for building machinelike nanodevices. G-quadruplex, as a new type of DNA secondary structures, can be harnessed to construct molecular device owing to its rich structural polymorphism. Herein, we developed a switching system based on G-quadruplexes and methylazacalix[6]pyridine (MACP6). The induced circular dichroism (CD) signal of MACP6 was used to monitor the switch controlled by temperature or pH value. Furthermore, the CD titration, Job-plot, variable temperature CD and 1H-NMR experiments not only confirmed the binding mode between MACP6 and G-quadruplex, but also explained the difference switching effect of MACP6 and various G-quadruplexes. The established strategy has the potential to be used as the chiral probe for specific G-quadruplex recognition.

A novel Ag+ sensor has been designed based on the mechanism that i-motif formation induced by Ag+ was sensitively recognized by a cyanine dye. The sensor exhibited an over 130–16,000 fold selectivity toward Ag+ than that toward other metal ions. This research not only provides a step forward toward the development of Ag+ detection but also represents a new application for i-motif DNA.

A probe for colorimetric detecting lead ion (Pb2+) has been designed by using a newly synthesized clip-like cyanine dye and G-quadruplex. The unique structure of the clip-like cyanine dye endowed the probe with a high selectivity towards Pb2+. Significant changes in absorption spectra of the cyanine dye recognizing the Pb2+ -induced conformational transition of G-quadruplexes made the probe show a high sensitivity towards Pb2+ with a detection limit of 1 nM. The excellent performance enabled the probe to be practically applied in measuring the Pb2+ pollution in freshwater system. (C) 2015 Elsevier B.V. All rights reserved.

Specific and sensitive identification of special G-quadruplex structures is an important issue and attracts increasing interest. In this paper, a novel, signal-amplified strategy is proposed for the specific detection of G-quadruplexes, which is very different from those currently-dominating methods based on single-molecular fluorescent probes. In this strategy, a ‘special designed’ cyanine dye loses the ability of self-assembly in solution but still keeps its assembly potential. When the G-quadruplex with a specific structure is present, the assembly potential of the dye is reactivated so that it can assemble to J-aggregates. Other DNA motifs without this specific structure cannot activate its assembly potential no matter if they are double-stranded or quadruplex DNA. Since the assembly is quite specific to structure, the induced procedure of the aggregates provides high specificity for this strategy. In addition, the attached aggregates exponentially amplify the signal due to the signal stacking of those monomers within the aggregates, which then significantly enhances the sensitivity of this strategy. As a result, this strategy exhibits a highly specific and sensitive detection ability for specific G-quadruplex structures both between quadruplexes and non-quadruplexes and among diverse quadruplex motifs.

A supramolecular probe is designed for visual detection of potassium based on a novel cyanine dye aggregate recognizing the motif transition of telomeric G-quadruplexes under the Na(+) background. The practical application for colorimetric measurement of urine potassium has been tested.

The H-aggregates of a novel cyanine dye, 3,3'-di(3-sulfopropyl)-4,5,4',5'-dibenzo-9-methyl-thiacarbocyanine triethylammonium salt (MTC), have been fabricated to verify hybrid/parallel intramolecular G-quadruplexes from linear duplex and single-strand DNAs under physiological conditions. The recognition is found to be successful both in solution and on Au film. These results have shown MTC H-aggregates, as a supramolecular system, may be used as a potential excellent probe for DNA structure, both in vitro and in vivo.

RNA G-quadruplexes (G4s) are one of the key components of the transcriptome that act as efficient post-transcriptional regulatory elements in living cells. To conduct further studies of the unique biological functions of RNA G4s, techniques need to be developed that can efficiently recognize RNA G4 structures under various conditions, in fixed cells and living cells, as well as in vitro. This paper presents the development of such a method, a new technique using a cyanine dye called CyT, which can detect both canonical and non-canonical RNA G4 structures from test tubes to living human cells. The ability of CyT to distinguish between G4 and nonG4 RNA offers a promising tool for future RNA G4-based biomarker discovery and potential diagnostic applications.

Biomolecules are promising templates that play important roles in controlling the supramolecular assembly process more flexibly and precisely due to their unique characteristic structures. Here we first present a G-quadruplex with a chair-like antiparallel motif as a novel dual-functional regulation template in the aggregation of a cyanine dye.

A G-quadruplex is identified which can exhibit two different motifs, respectively, corresponding to Na(+) and K(+). The relative amount of each motif is related to the Na(+)/K(+) ratio. Based on selective recognition of the G-quadruplex motifs by a cyanine dye aggregate, a method for both colorimetric and quantitative measurements of Na(+)/K(+) ratios is constructed.